International Journal of Pharmaceutics (v.301, #1-2)
TITLE PAGE (EDI BOARD) (iii).
High speed DSC (hyper-DSC) as a tool to measure the solubility of a drug within a solid or semi-solid matrix by Daniela Gramaglia; Barbara R. Conway; Vicky L. Kett; R. Karl Malcolm; Hannah K. Batchelor (1-5).
Conventional differential scanning calorimetry (DSC) techniques are commonly used to quantify the solubility of drugs within polymeric-controlled delivery systems. However, the nature of the DSC experiment, and in particular the relatively slow heating rates employed, limit its use to the measurement of drug solubility at the drug's melting temperature. Here, we describe the application of hyper-DSC (HDSC), a variant of DSC involving extremely rapid heating rates, to the calculation of the solubility of a model drug, metronidazole, in silicone elastomer, and demonstrate that the faster heating rates permit the solubility to be calculated under non-equilibrium conditions such that the solubility better approximates that at the temperature of use. At a heating rate of 400 °C/min (HDSC), metronidazole solubility was calculated to be 2.16 mg/g compared with 6.16 mg/g at 20 °C/min.
Keywords: High-speed DSC; Solubility; Metronidazole; Silicone;
Enhancement of the stability of BCNU using self-emulsifying drug delivery systems (SEDDS) and in vitro antitumor activity of self-emulsified BCNU-loaded PLGA wafer by Gang Soo Chae; Jin Soo Lee; Seon Hwa Kim; Kwang Su Seo; Moon Suk Kim; Hai Bang Lee; Gilson Khang (6-14).
The main purpose of this study was to develop self-emulsifying drug delivery systems (SEDDS) for the improvement of the stability of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) after released from poly (d,l-lactide-co-glycolide) (PLGA) wafer and to evaluate its in vitro antitumor activity against 9L gliosarcoma cells. The in vitro stability test of BCNU was characterized by the BCNU amount in phosphate buffered saline (PBS, pH 7.4) at 37 °C. SEDDS increased in vitro half-life of BCNU up to 130 min compared to 45 min of intact BCNU. Self-emulsified (SE) BCNU was fabricated into wafers with flat and smooth surface by compression molding. In vitro release of BCNU from SE BCNU-loaded PLGA wafer was prolonged up to 7 days followed first order release kinetics. Beside, the cytotoxicity of SE BCNU-loaded PLGA wafer against 9L gliosarcoma cells was higher than intact BCNU-loaded PLGA wafer which is more susceptible to hydrolysis. SE BCNU degraded much more slowly than the intact BCNU in PLGA matrix at 25 °C. These results strongly suggest that the self-emulsion system increased the stability of BCNU after released from PLGA wafer. From these results, it could be expected that the penetration depth of BCNU could be improved in brain tissue using self-emulsion system.
Keywords: Brain tumor; Self-emulsifying drug delivery system (SEDDS); 1,3-Bis(2-chloroethyl)-1-nitrosourea (BCNU);
Multivesicular liposome formulation for the sustained delivery of breviscapine by Haijun Zhong; Yingjie Deng; Xiumin Wang; Binghua Yang (15-24).
Breviscapine, a well-known bioactive flavonoid ingredient extracted from the traditional Chinese medicine, has been extensively used in clinic to treat ischemic cerebrovascular and cardiovascular diseases in China. In order to prolong the duration of the drug in the circulation, reduce the frequency of injection administration and subsequently afford patient compliance, multivesicular liposome (MVL, namely DepoFoam) was utilized as a sustained-delivery system for breviscapine. In vitro release and in vivo pharmacokinetics of MVLs containing breviscapine (bre-MVLs) following intramuscular injection to rats were investigated compared with those of traditional liposomes containing breviscapine (bre-TLs). The drug durations both in vitro and in vivo were significantly prolonged for the bre-MVL, and that the drug release in vitro and the absorption in vivo showed a good linear correlation (R = 0.9834), which provided an evidence for the suitability to select human plasma as the medium of drug release from MVLs in vitro. Drug release from bre-MVLs (triolein/tricaprylin, 10/0) in vitro extended a long period of 5–6 days, while the bre-TLs released 80% within only 4 h. The mean residence time (MRT) obtained from the pharmacokinetics study of bre-MVL was about 16.6- and 5.04-fold longer than those of breviscapine solution (BS) and bre-TL, respectively. A duration in vivo for a period of 4–5 days was fulfilled for bre-MVL. In conclusion, MVL can be successfully used as a sustained delivery system of breviscapine.
Keywords: Breviscapine; Multivesicular liposomes; Sustained delivery; In vitro–in vivo correlation;
Reducing bounce effects in the Andersen cascade impactor by Craig Dunbar; Abdo Kataya; Tiba Tiangbe (25-32).
The collection efficiency of the Andersen cascade impactor (ACI) can be affected by particle bounce, overload and re-entrainment (or blow-off), collectively referred to as bounce effects. Reduction of bounce effects in the ACI operated at 60 LPM was investigated for placebo large porous particles. Aerodynamic particle size distributions (aPSDs) obtained with the ACI and multi-stage liquid impinger (MSLI) were compared by observation of modes and statistical comparisons of the mass median aerodynamic diameter (MMAD) and geometric standard deviation (σ g). Particle bounce effects were prevalent in the ACI with uncoated plates, i.e., bi-modal distribution with statistically significant differences in MMAD and σ g (P < 0.05). Coating the impaction plates with a thin layer of vacuum grease and decreasing the ACI stage jet velocities reduced, but did not minimize bounce effects. Bounce effects were minimized using 20-μm pore glass fiber filters saturated in water placed on inverted impaction plates, with good agreement obtained between the ACI and MSLI aPSDs, i.e., mono-modal with no statistically significant differences in MMAD and σ g (P > 0.05). Selection of the impaction substrate material and solvent must be evaluated with the drug product and analytical methods to minimize bounce effects and obtain an accurate measure of the aPSD.
Keywords: Bounce effects; Cascade impaction; Large porous particles;
Thermal behaviour and stability in Olanzapine by Griselda I. Polla; Daniel R. Vega; Hilda Lanza; Dora G. Tombari; Ricardo Baggio; Alejandro Pedro Ayala; Josué Mendes Filho; Daniel Fernández; Gabriela Leyva; Gustavo Dartayet (33-40).
The stability and thermal behaviour of two anhydrate phases and a new mixed water:DMSO solvate of Olanzapine (2-methyl-4-(4-methyl-1-piperazinyl)-10H-thieno-[2,3-b][1,5]benzodiazepine) are studied by different methods: differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD) and Raman scattering (RS). Single crystal structural data for the latter phase are presented, confirming the presence of the (Olanzapine)2 dimer as the structural building unit of all known phases of the drug, either anhydrate or solvated.An apparent interconversion between both solid state forms is shown to be an artifact and explained in terms of a melting–recrystallization process.
Keywords: Olanzapine; Polymorphism; Stability;
Thymosin-loaded enteric microspheres for oral administration: Preparation and in vitro release studies by Ju Fei Yang; Li Yan Qiu; Yi Jin; Jian Xiang Zhang (41-47).
Thymosin, a water-soluble polypeptide compound, was encapsulated within enteric microspheres of acrylic acid resin II by modified oil in oil (o/o) emulsion solvent evaporation method. The mixture emulsifier composed of lecithin and Span 80 was critical to the formation of sphere-shaped thymosin microparticles. Optimizing process parameters, such as the volume ratio of organic solvent to water, initial drug feed and polymer concentration, resulted in high drug encapsulation efficiency of 89.7% (6% polymer concentration and 0.5% initial drug feed). In vitro release studies suggested that thymosin release from microspheres exhibited pH dependent profiles. For formulation with 6% polymer concentration and 0.5% initial drug feed, 68.7% thymosin was released within 4 h in pH 6.8 PBS buffer, while only 6.5% was observed in acid medium.
Keywords: Thymosin; Acrylic acid resin; Microspheres; Emulsion solvent evaporation method;
Decreasing malathion application time for lice treatment reduces transdermal absorption by Rhonda M. Brand; Anna R. Charron; Randall E. Brand (48-53).
Head lice are the most common parasitic infestation in the United States requiring topical treatment with pediculicides. Ovide®, the 0.5% malathion formulation used in treatment of head lice requires placement on dry hair for 8–12 h. Malathion, however, is effective at killing lice and nits in 10 min. Our concern of over exposing children to malathion has led us to examine whether significantly more malathion will penetrate transdermally when applied for the recommended 8 h than for a shorter but apparently equally effective period.In vitro absorption studies were performed across haired rat skin and human abdominal skin to determine whether reducing malathion application time decreased skin absorption.A 0.5 h exposure caused 0.36 ± 0.14% of the donor malathion to penetrate through human skin after 24 h and 2.1 ± 0.6% remained in the skin after washing with shampoo. After 8 h of topical applications penetration was approximately three-fold greater (1.02 ± 0.41) and 3.4 ± 0.5% remained in the skin (p < 0.05 versus 0.5 h). The relationship between absorption and exposure time also occurred for haired rat skin (p < 0.05). This differential continued for 72 h even after removal of the source.Significantly less malathion penetrated from Ovide® after 0.5 h versus the suggested 8 h application, without decreasing the product's efficacy. Further clinical studies in children are warranted to confirm the efficacy of this shortened application time.
Keywords: Head lice; Malathion; Transdermal;
Physicochemical characterization and in vivo evaluation of poloxamer-based solid suppository containing diclofenac sodium in rats by Chul Soon Yong; Yu-Kyoung Oh; Yong-Il Kim; Jong Oh Kim; Bong-Kyu Yoo; Jong-Dal Rhee; Kang Choon Lee; Dae-Duk Kim; Young-Joon Park; Chong-Kook Kim; Han-Gon Choi (54-61).
To develop a poloxamer-based solid suppository with poloxamer mixtures, the melting point of various formulations composed of poloxamer 124 (P 124) and poloxamer 188 (P 188) were investigated. The dissolution and pharmacokinetic study of diclofenac sodium delivered by the poloxamer-based suppository were performed. Furthermore, the identification test in the rectum and morphology test of rectal tissues were carried out after its rectal administration in rats. The poloxamer mixtures composed of P 124 and P 188 were homogeneous phases. Very small amounts of P 188 affected the melting point of poloxamer mixtures. In particular, the poloxamer mixture [P 124/P 188 (97/3%)] with the melting point of about 32 °C was a solid form at room temperature and instantly melted at physiological temperature. Very small amounts of P 188 hardly affected the dissolution rates of diclofenac sodium from the suppository. Dissolution mechanism analysis showed the dissolution of diclofenac sodium was proportional to the time. The poloxamer-based suppository gave significantly higher initial plasma concentrations and faster T max of diclofenac sodium than did conventional PEG-based suppository, indicating that the drug from poloxamer-based suppository could be absorbed faster than that from PEG-based one in rats. It retained in the rectum for at least 4 h and could not irritate or damage the rectal tissues of rats. Thus, the poloxamer-based solid suppository with P 124 and P 188 was a mucoadhesive, safe and effective rectal dosage form for diclofenac sodium.
Keywords: Diclofenac sodium; Poloxamer 124; Poloxamer 188; Mucoadhesive; Poloxamer-based solid suppository; Pharmacokinetics;
The effects of bivalent inorganic salts on the mucoadhesive performance of a polymethylmethacrylate sodium salt by Francesco Cilurzo; Francesca Selmin; Paola Minghetti; Luisa Montanari (62-70).
The effects of bivalent inorganic salts, namely CaCl2, MgCl2, MgSO4, ZnCl2 and ZnSO4, on the mucoadhesive performance of a polymethylmethacrylate sodium salt (EuSNa) were investigated. The swelling properties and mucoadhesion of ten different blends made of EuSNa and 5 or 10% (m/m) inorganic salts were evaluated. Only the addition of Zn salts caused a significant reduction of mucoadhesive properties and an increase of swelling. Swelling and mucoadhesive properties of the linear polymethylmethacrylate salt were affected by a physical cross-linking due to bivalent cations. The extent of such interaction may be mainly ascribed to the different electronegativity of the bivalent cations. Attenuated total reflectance infrared spectroscopy (ATR-FTIR) and texture analysis supported this hypothesis.Adding magnesium and calcium salts, the intrinsic dissolution rate of EuSNa decreased of at least 25%. Mucoadhesive tablets were prepared with the most suitable blends and tested on human healthy volunteers. The addition of the magnesium and calcium increased the in vivo permanence time without affecting the mucoadhesive performances. The lack of swelling, mucosal irritation and unpleasant sensation allow the use of such blends in the preparation of mucoadhesive tablets.
Keywords: Polymethylmethacrylate sodium salt; Buccal tablets; Mucoadhesion; ATR-FTIR spectroscopy;
Synthesis and transdermal penetration of NSAID glycoside esters by Henk Swart; Jaco C. Breytenbach; Jonathan Hadgraft; Jeanetta du Plessis (71-79).
The glucoside and mannoside derivatives of the NSAIDs flurbiprofen, ibuprofen, ketoprofen and naproxen were synthesised and their penetration through human skin was determined. Experimental transdermal flux data showed that the parent NSAIDs penetrated human skin to a much higher extent than the glycosides.
Keywords: Flurbiprofen; Ibuprofen; Ketoprofen; Naproxen; Glycoside; Transdermal penetration;
A combined cell based approach to identify P-glycoprotein substrates and inhibitors in a single assay by Praveen V. Balimane; Saeho Chong (80-88).
The objective of this project was to develop a cell based in vitro experimental procedure that can differentiate P-glycoprotein (P-gp) substrates from inhibitors in a single assay. Caco-2 cells grown to confluency on 12-well Transwell® were used for this study. The efflux permeability (B to A) of P-gp specific probe (viz., digoxin) in the presence of test compounds (e.g. substrates, inhibitors and non-substrates of P-gp) was monitored, and the influx permeability (A to B) of test compounds was evaluated after complete P-gp blockade. Radiolabelled digoxin was added on the basolateral side with buffer on the apical side. The digoxin concentration appearing on the apical side represents digoxin efflux permeability during the control phase (0–1 h period). After 1 h, a test compound (10 uM) was added on the apical side. The reduced efflux permeability of digoxin suggests that the added test compound is an inhibitor. The influx permeability of test compound is also determined during the 1–2 h study period by measuring the concentration of the test compound in the basolateral side. At the end of 2 h, a potent P-gp inhibitor (GF120918) was added. The increased influx permeability of test compound during the 2–3 h incubation period indicates that the added test compound is a substrate. Samples were taken from both sides at the end of 1–3 h and the concentrations of the test compounds and digoxin were quantitated. Digoxin efflux permeability remained unchanged when incubated with P-gp substrates (e.g., etoposide, rhodamine123, taxol). However, when a P-gp inhibitor was added to the apical side, the digoxin efflux (B to A permeability) was significantly reduced (ketoconazole = 51% reduction) as expected. The influx permeability of substrates increased significantly (rhodamine123 = 70%, taxol = 220%, digoxin = 290%) after the P-gp inhibitor (GF120918) was introduced, whereas the influx permeability of P-gp inhibitor and non-substrates was not affected by GF120918. Thus, this combined assay provides an efficient cell based in vitro screening tool to simultaneously distinguish compounds that are P-gp substrates from P-gp inhibitors.
Keywords: Permeability; Efflux; Caco-2 cell; High-throughput; P-glycoprotein; Inhibitor; Substrate;
Sequential design of a novel PVA-based crosslinked ethylenic homopolymer for extended drug delivery by Viness Pillay; Wilbert Sibanda; Michael P. Danckwerts (89-101).
A Box–Behnken Design was employed to study the influence of boric acid, sodium sulfate, ammonia and n-propanol in the formulation of crosslinked ethylenic homopolymeric (CEH) gelispheres from native polyvinyl alcohol (PVA). The dependent variables studied included the size of the spherical gelispheres, drug encapsulation efficiency, in vitro dissolution after 30 min and textural parameters, namely fracture force and matrix rupture energy. Based on these responses, an optimized CEH gelisphere matrix was formulated and thereafter incorporated as a powder into a candidate crosslinked zinc–pectinate multiple-unit device to assess its effect on modifying drug release. In the case of the CEH-loaded zinc–pectinate gelispheres, it was determined via constrained optimization that a maximum drug encapsulation efficiency of 28.63% could be obtained under the conditions of 0% (w/v) CEH, 13 h of crosslinking and drying temperature of 60 °C. On the other hand, initial drug release could be significantly retarded when 0.10% (w/v) of CEH was included in the formulation and crosslinked for 24 h at 40 °C. In this regard, CEH induced a 4 h lag phase. Furthermore, zero-order drug release was produced and could be maintained over several weeks. Kinetic analysis of drug release further supported that CEH inhibits polymer relaxation (k 2 ≪ k 1), and hence slows down drug diffusion. Based on these results, the CEH-zinc–pectinate drug delivery system appears to be a suitable carrier that may be employed for long-term administration for, e.g. via subcutaneous implantation.
Keywords: Polyvinyl alcohol; Crosslinked ethylenic homopolymeric gelispheres; Experimental Design;
Dynamic swelling behavior of γ-radiation induced polyelectrolyte poly(AAm-co-CA) hydrogels in urea solutions by Erdener Karadağ; Ömer Barış Üzüm; Dursun Saraydin; Olgun Güven (102-111).
The aim of this study was to investigate the equilibrium swelling properties in urea solutions of γ-radiation induced polyelectrolyte copolymeric hydrogels consisting of acrylamide (AAm) and crotonic acid (CA). Poly(acrylamide-co-crotonic acid), poly(AAm-co-CA) hydrogels containing different amounts of CA were obtained in the form of rods after radiation. Swelling experiments were performed in aqueous urea solutions at 25 °C, gravimetrically. The hydrogels showed large extents of swelling in aqueous (urea/water) media the swelling being highly dependent on the chemical composition of the hydrogels and irradiation dose. The percentage swelling of poly(AAm-co-CA) hydrogels was between 1160 and 4250%, while that of the AAm hydrogels was between 670 and 900%. The diffusional exponent values (n) are between 0.51 and 0.66, hence the diffusion of urea/water into the hydrogels is non-Fickian. Equilibrium urea/water contents of the hydrogel systems were changed between 0.870 and 0.977.
Keywords: γ-Radiation; Swelling; Diffusion; Acrylamide/crotonic acid; Hydrogel; Urea;
Physicochemical characterization and mechanisms of release of theophylline from melt-extruded dosage forms based on a methacrylic acid copolymer by Christopher R. Young; Caroline Dietzsch; Matteo Cerea; Thomas Farrell; Kurt A. Fegely; Ali Rajabi-Siahboomi; James W. McGinity (112-120).
The purpose of the current study was to investigate the physicochemical properties of melt-extruded dosage forms based on Acryl-EZE® and to determine the influence of gelling agents on the mechanisms and kinetics of drug release from thermally processed matrices. Acryl-EZE® is a pre-mixed excipient blend based on a methacrylic acid copolymer that is optimized for film-coating applications. Powder blends containing theophylline, Acryl-EZE®, triethyl citrate and an optional gelling agent, Methocel® K4M Premium (hydroxypropyl methylcellulose, HPMC, hypromellose 2208) or Carbopol® 974P (carbomer), were thermally processed using a Randcastle single-screw extruder. The physical and chemical stability of materials during processing was determined using thermal gravimetric analysis and HPLC. The mechanism of drug release was determined using the Korsmeyer–Peppas model and the hydration and erosion of tablets during the dissolution studies were investigated. The excipient blends were physically and chemically stable during processing, and the resulting dosage forms exhibited pH-dependent dissolution properties. Extrusion of blends containing HPMC or carbomer changed the mechanism and kinetics of drug release from the thermally processed dosage forms. At concentrations of 5% or below, carbomer was more effective than HPMC at extending the duration of theophylline release from matrix tablets. Furthermore, carbomer containing tablets were stable upon storage for 3 months at 40 °C/75% RH. Thus, hot-melt extrusion was an effective process for the preparation of controlled release matrix systems based on Acryl-EZE®.
Keywords: Melt-extrusion; Methacrylic acid copolymer; Eudragit® L 100-55; Acryl-EZE®; Carbomer; Hydroxypropyl methylcellulose;
Formulation of an ophthalmic lipid emulsion containing an anti-inflammatory steroidal drug, difluprednate by Masazumi Yamaguchi; Shin-ichi Yasueda; Akiharu Isowaki; Makiko Yamamoto; Masako Kimura; Katsuhiro Inada; Akira Ohtori (121-128).
Preparation of oil-in-water (o/w) type lipid emulsion is one of the approaches to formulate drugs that are poorly water-soluble but can be dissolved in the oil phase of the emulsions. A synthetic glucocorticoid medicine, difluprednate (DFBA), is a water-insoluble compound. We formulated DFBA (0.05%, w/v) ophthalmic lipid emulsion containing 5.0% (w/v) caster oil and 4.0% (w/v) polysorbate 80. The appearance of the emulsion was blue and translucent lipid emulsion, and the median particle size of the lipid emulsion was 104.4 nm. Neither separation nor change in particle size was observed after 6 months at 40 °C. Furthermore, when compared with DFBA (0.05%, w/v) ophthalmic suspension, the lipid emulsion showed 5.7-fold higher concentration of DFB that was an active metabolite of DFBA in aqueous humor at 1 h after instillation. Ophthalmic lipid emulsion enhances the intraocular penetration of drugs, and it is useful as a delivery system for the ophthalmic preparations of lipophilic drugs.
Keywords: Lipid emulsion; Polysorbate 80; Difluprednate; Intraocular penetration;
The effect of unsaturated fatty acids in benzyl alcohol on the percutaneous permeation of three model penetrants by Gihan R. Nanayakkara; Ann Bartlett; Ben Forbes; Chris Marriott; Phil J. Whitfield; Marc B. Brown (129-139).
The model penetrants butyl paraben (BP), methyl paraben (MP) and caffeine (CF), because of their different octanol/water partition coefficients and postulated routes of permeation through human skin, were selected to assess the enhancing activity of pre-treatment solutions consisting of monounsaturated (oleic (OA) and palmitoleic (PA)) and poly-unsaturated (linoleic (LA)) fatty acids in benzyl alcohol (BA) using Franz diffusion cells and HPLC detection. Prior to assessing the effect of penetrant lipophilicity, MP was chosen to investigate the concentration-dependent effect of fatty acids in pre-treatment solutions. At 5% (w/w) fatty acids in BA, only pre-treatment solutions containing palmitoleic acid (PA) increased the permeation of MP when compared to pre-treatment with BA alone, whereas at higher concentrations (10 and 20%, w/w), all pre-treatment solutions except 10% OA produced a significant increase in MP flux (P < 0.05). The general order of fatty acid effectiveness at any concentration was PA > LA > OA. At 20% (w/w) fatty acids in BA, all pre-treatment solutions significantly enhanced the permeation of all three penetrants (P < 0.05) and an inverse relationship between penetrant lipophilicity and enhancement effect was observed. The permeation of BP was enhanced to a similar extent by all three fatty acids, whereas PA caused a significantly greater enhancement in the flux of both MP and CF when compared to OA, LA and controls (P < 0.05). It was proposed that the synergetic enhancement mechanisms of fatty acids and BA in pre-treatment solutions were augmenting the polar route by way of interactions with both polar and non-polar regions of stratum corneum lipids. Furthermore, the combination of PA and BA appears to be a good candidate as a penetration enhancer for hydrophilic molecules.
Keywords: Palmitoleic acid; Fatty acids; Benzyl alcohol; Transdermal; Lipophilicity;
Characterisation and in vitro evaluation of bioadhesive liposome gels for local therapy of vaginitis by Željka Pavelić; Nataša Škalko-Basnet; Ivan Jalšenjak (140-148).
The purpose of this study was to design and evaluate a new vaginal delivery system for the local treatment of vaginitis. Liposomes containing two commonly applied drugs in the treatment of vaginal infections, namely clotrimazole and metronidazole, were prepared by the proliposome and the polyol dilution methods. Both types of liposomes were characterised and compared for particle size, polydispersity, entrapment efficiency, and tested for in vitro stability in media that mimic human vaginal conditions (buffer, pH 4.5, and vaginal fluid simulant). To achieve application viscosity and to further improve their stability, liposomes containing drugs were incorporated in a bioadhesive gel made of Carbopol® 974P NF resin. In vitro release studies have demonstrated that even after 24 h of incubation in vaginal fluid simulant (at 37 °C) more than 30% of the originally entrapped clotrimazole (or 50% of metronidazole) was still retained in the gel. Storage stability studies have proved the ability of Carbopol® 974P NF gel to preserve original size distributions of incorporated liposomes. All the performed experiments confirm the applicability of bioadhesive liposome gels as a novel delivery system for local therapy of vaginal infections.
Keywords: Liposomes; Clotrimazole; Metronidazole; Bioadhesive gel; Stability; Vaginal infections;
Influence of particle size, antigen load, dose and additional adjuvant on the immune response from antigen loaded PLA microparticles by Yogesh K. Katare; T. Muthukumaran; Amulya K. Panda (149-160).
Polylactide (PLA) polymer particles entrapping tetanus toxoid (TT) were evaluated in terms of particle size, antigen load, dose and additional adjuvant for achieving high and sustained anti-TT antibody titer from single point intramuscular immunization. Admixture of polymer entrapped TT and alum improved the immune response in comparison to particle-based immunization. High and long lasting antibody titer was achieved upon immunization with 2–8 μm size particles. Microparticles within the size range 50–150 μm elicited very low serum antibody response. Immunization with very small particles (<2 μm) and with intermediate size range particles (10–70 μm) elicited comparable antibody response from single point immunization but lower in comparison to that achieved while immunizing with 2–8 μm size particles. Potentiation of antibody response on immunization of admixture of microparticles and alum was also dependent on particle size. These results indicate the need of optimal particle sizes in micron ranges for improved humoral response from single point immunization. Increasing antigen load on polymer particles was found to have positive influence on generation of antibody titers from particle based immunization. Maximum peak antibody titer of ∼300 μg/mL was achieved on day 50 upon immunization with particles having highest load of antigen (94 μg/mg of polymer). Increase in dose of polymer entrapped antigen resulted in concomitant increase in peak antibody titers indicating the importance of antigen stability, particle size and load on generating reproducible immune response. Optimization of particle size, antigen load, dose and use of additional adjuvant resulted in high and sustained anti-TT antibody titers over a period of more than 250 days from single point immunization. Serum anti-TT antibody titers from single point immunization of admixrure of PLA particles and alum was comparable with immunization from two divided doses of alum adsorbed TT.
Keywords: PLA particles; Tetanus toxoid; Particle size; Antigen load; Antibody response;
Effect of counterions on the physical properties of l-arginine in frozen solutions and freeze-dried solids by Ken-Ichi Izutsu; Yasuto Fujimaki; Akiko Kuwabara; Nobuo Aoyagi (161-169).
The objective of this study was to elucidate the physical properties of l-arginine and various counterion combinations in frozen aqueous solutions and in freeze-dried solids. l-Arginine remains amorphous in the highly concentrated non-ice phase in frozen solutions with a T ′ g (glass transition temperature of maximally freeze-concentrated solutes) of −41.4 °C. Some acids and salts (e.g., H3PO4, H2SO4, HNO3, and NaH2PO4) raised the T ′ g , whereas others (e.g., HCl, CH3COOH, HCOOH, Na2HPO4, and NaCl) had little effect or lowered the l-arginine T ′ g . Co-lyophilization with phosphoric acid also raised the glass transition temperature (T g) of amorphous freeze-dried l-arginine solids. Arginine–H3PO4 combinations exhibited properties that led to either the stabilization or destabilization of a model protein (lactate dehydrogenase: LDH) during freeze-drying, depending on their concentration ratios. Fourier-transform infrared (FT-IR) and diffusion reflectance near-infrared (NIR) spectra indicated the presence of interactions between the amino and/or guanidyl groups of l-arginine and phosphate ions in the amorphous freeze-dried cakes. It was postulated that the interaction between l-arginine and the multivalent counterions, as well as an increase in hydrogen bonding network, reduced the mobility of molecules in the frozen solutions and freeze-dried solids.
Keywords: Freeze-drying; Near-infrared Spectroscopy; Amorphous solid; Glass transition;
Spray-dried Amioca® starch/Carbopol® 974P mixtures as buccal bioadhesive carriers by D. Ameye; D. Mus; P. Foreman; J.P. Remon (170-180).
In the present study, spray-dried Amioca® starch/Carbopol® 974P mixtures were evaluated as potential buccal bioadhesive tablets. Carbopol® (C 974P) concentrations from 5 to 75% were tested. All spray-dried mixtures showed a comparable or better bioadhesive capacity compared to a reference formulation (DDWM/C 974P 95/5). The bioadhesive capacities of Amioca®/Carbopol® 974P mixtures were improved by spray-drying. All spray-dried mixtures showed significantly higher work of adhesion values compared to their equivalent physical mixtures. The influence of Carbopol® concentration on the in vivo adhesion time of placebo tablets and in vitro miconazole nitrate release was tested. The ratio Amioca®/C 974P 70/30 showed the longest in vivo adhesion time (24.5 ± 8.5 h). Lower and higher C 974P concentrations had a shorter in vivo adhesion time. The mixtures containing between 15 and 30% C 974P could all sustain the in vitro miconazole nitrate release over 20h. Again, lower and higher C 974P concentrations showed a faster in vitro miconazole release. The drug loading capacity of a spray-dried mixture containing 20% C 974P was investigated in vivo in dogs using testosterone as model drug. The spray-dried mixture could be loaded with 60% drug without loosing its in vivo bioadhesive and pharmacokinetic properties.
Keywords: Spray-dried Amioca®/Carbopol® 974P mixtures; Buccal; Bioadhesion; In vitro/in vivo bioavailability;
The development of DMA for the detection of amorphous content in pharmaceutical powdered materials by Paul G. Royall; Ching-ya Huang; See-wah Jai Tang; John Duncan; Glynn Van-de-Velde; Marc B. Brown (181-191).
The aim of this short study was to develop a novel method of sample presentation that will allow currently available DMA apparatus designed for the testing of self-supporting materials to detect amorphous content in controlled mixtures of amorphous and crystalline powders. The preparation of amorphous lactose was carried out by spraying drying, using a Büchi mini spray drier. Controlled mixtures of amorphous and crystalline lactose were produced to give eight samples ranging between 2% and 75% (w/w) amorphous content. These powdered mixtures were loaded into the DMA using a novel powder-pocket device, which consisted of folded sheet of stainless steel. The pocket was clamped directly into the DMA using a single cantilever configuration, and subjected to oscillating displacement, forcing horizontal shearing of the powder between the two plates of the pocket. Typical experimental parameters were a dynamic displacement of 0.05 mm with a frequency of 1 Hz and a heating rate of 5 °C/min, from 25 °C to 250 °C. Over the glass transition region of amorphous lactose, the storage modulus decreased rapidly and a peak was observed in the tan δ signal, which are typical DMA responses for self-supporting glassy materials over their glass transition region. In both the storage modulus and tan δ signals, contributions from both plasticized and non-plasticized amorphous lactose were demonstrated. Such an observation was caused by the powder pocket restricting the loss of the 2.5% (w/w) water present in the spray-dried lactose within the time scale of the first heating cycle. The tan δ peak for the non-plasticized amorphous lactose showed Arrhenius behaviour as function of oscillation frequency. The relationship between the increase in the tan δ peak with increasing frequency allowed the determination of an activation energy that was comparable to the literature values for similar compounds. The height of the tan δ peak for the non-plasticized material was directly proportional to the amount of amorphous lactose present in the mixtures. The glass transition response was still detectable in mixtures containing as little as 2% (w/w) amorphous content, however the theoretical limit of detection was higher than that determined for the same mixtures using solution calorimetry. The results demonstrate that the novel powder pocket allows the use of conventional DMA instruments for the analysis of pharmaceutical powders, however the technique requires more development to further reduce its theoretical limit of detection.
Keywords: DMA; Amorphous powders; Glass transition; Powder pocket; Lactose;
The effect of the solvent on the film-forming parameters of hydroxypropyl-cellulose by János Bajdik; Géza Regdon; Tamás Marek; István Erős; Károly Süvegh; Klára Pintye-Hódi (192-198).
In pharmaceutical technology, film-forming agents are often applied in solution during the preparation of solid dosage forms. A wide range of polymers have already been examined, but many of the effects of the applied solvent on the properties of the film are still not fully known. The study of these phenomena might be of great help in the preparation of better films. In the present study, the frequently used polymer hydroxypropyl-cellulose was examined in water and ethanol. The latter solvent exhibits better wetting properties for this polymer. It was found that the use of ethanol enhanced the processibility because of the easier atomization and the shorter drying period. Properties characteristic of the chemical nature (wetting, surface free energy and thermal properties) and the physical behaviour (deformation process) of the poured films were studied. Relevant differences were detected only in the mechanical parameters. The sizes of the free volume holes in the differently prepared polymers were also determined, but this parameter proved irrelevant as concerns alterations of the breaking process. The explanation of the differences processibility of the films might be the different strengths of binding between the macromolecular chains. This phenomenon can also explain the different degrees of hydration of the polymer and the changes in the drying process.
Keywords: HPC; Investigation of solutions; Deformation process; Polymer film; Solvent;
Improved physicochemical characteristics of felodipine solid dispersion particles by supercritical anti-solvent precipitation process by Dong-Han Won; Min-Soo Kim; Sibeum Lee; Jeong-Sook Park; Sung-Joo Hwang (199-208).
Solid dispersions of felodipine were formulated with HPMC and surfactants by the conventional solvent evaporation (CSE) and supercritical anti-solvent precipitation (SAS) methods. The solid dispersion particles were characterized by particle size, zeta potential, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), solubility and dissolution studies. The effects of the drug/polymer ratio and surfactants on the solubility of felodipine were also studied. The mean particle size of the solid dispersions was 200–250 nm; these had a relatively regular spherical shape with a narrow size distribution. The particle size of the solid dispersions from the CSE method increased at 1 h after dispersed in distilled water. However, the particle sizes of solid dispersions from the SAS process were maintained for 6 h due to the increased solubility of felodipine. The physical state of felodipine changed from crystalline to amorphous during the CSE and SAS processes, confirmed by DSC/XRD data. The equilibrium solubility of the felodipine solid dispersion prepared by the SAS process was 1.5–20 μg/ml, while the maximum solubility was 35–110 μg/ml. Moreover, the solubility of felodipine increased with decreasing drug/polymer ratio or increasing HCO-60 content. The solid dispersions from the SAS process showed a high dissolution rate of over 90% within 2 h. The SAS process system may be used to enhance solubility or to produce oral dosage forms with high dissolution rate.
Keywords: Felodipine; Solid dispersion; Supercritical anti-solvent precipitation;
Novel lipid-based formulations enhancing the in vitro dissolution and permeability characteristics of a poorly water-soluble model drug, piroxicam by Sunil Prabhu; Maru Ortega; Chan Ma (209-216).
Lipid-based delivery systems are becoming increasingly popular as carriers of drugs due to their ability to overcome barriers to oral absorption. The purpose of this study was to prepare novel lipid-based formulations of a model drug, piroxicam (PXCM), a poorly water-soluble non-steroidal anti-inflammatory drug (NSAID) using 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) phospholipid alone, and in combination with polyethylene glycol (PEG 4600). Lipid-based drug delivery systems were prepared using conventional methods of preparation and the following aspects were evaluated (1) in vitro dissolution behavior, (2) absorption via Caco-2 cell monolayers and (3) stability of formulations over a 12-month period. In addition, physical characterization studies using differential scanning calorimetry (DSC) were also performed. Formulations of PXCM were prepared using DMPC in the following combinations (A) 1:1 and (B) 2:1 and a mixture of DMPC and PEG 4600 (C) 2:1:1, respectively. Dissolution studies conducted in phosphate buffered saline (PBS, pH 7.4, 37 ± 0.5 °C) using the USP type II (paddle) dissolution apparatus showed an increase in dissolution rate and extent of the PXCM from all solid dispersion formulations when compared to the control. As such, the rate of drug release was observed to be fastest with formulation (C) showing the greatest increase of over two-fold compared to the control. Release of PXCM from formulations (A) and (B) was intermediate with the latter showing superior dissolution behavior despite containing lower amounts of the carrier lipid than the former. This observation indicates a possible existence of threshold levels for phospholipids carriers beyond which dissolution could be adversely affected. DSC studies further confirmed the dissolution behavior of these formulations demonstrating different levels of amorphous to crystalline nature. Results of HPLC analysis from Caco-2 cell culture studies showed increase in transport of PXCM from all formulations, with formulation (C) showing the maximum increase followed by formulations (B) and (A), when compared to control. The apparent permeability coefficients (P app) were calculated to be 7.92 × 10−6, 9.48 × 10−6, 9.2 × 10−6 and 5.6 × 10−6 cm/s for formulations (A)–(C) and control, respectively. Overall, permeation appeared to improve for all formulations over the control. Stability studies at various temperatures showed all formulations to have good stability for the first 6 months; then a decline in dissolution rates was observed, especially for PEG-based lipid carrier systems, attributed to the increase in crystalline content of the solid dispersions upon storage.
Keywords: Lipid-based drug delivery systems; Poorly water-soluble drugs; Dissolution; Permeability; DSC; DMPC; PEG 4600; Stability;
Controlled release of levonorgestrel from biodegradable poly(d,l-lactide-co-glycolide) microspheres: In vitro and in vivo studies by S.H. Wang; L.C. Zhang; F. Lin; X.Y. Sa; J.B. Zuo; Q.X. Shao; G.S. Chen; S. Zeng (217-225).
Poly(d,l-lactide-co-glycolide) (PLG) biodegradable microspheres containing a contraceptive drug, levonorgestrel (LNG), were prepared using both the solvent evaporation method and a modified solvent extraction–evaporation method. The microspheres prepared with the solvent evaporation process had porous surfaces with low product yields and poor encapsulation efficiencies. On the other hand, the microspheres prepared using the modified solvent extraction–evaporation method were nonporous with encapsulation efficiencies close to 100%. In vitro drug release showed the nonporous microspheres had a lower initial burst and a slightly prolonged duration of release than those porous microspheres. In vivo release kinetics of the low burst microspheres were determined by measuring LNG plasma levels after a single intramuscular injection to female rats. At a LNG dose of 41.1 mg/kg, average plasma LNG levels were 6–10 ng/ml in the first 24 h and subsequently remained above 1 ng/ml until 126 days. The duration above the minimum effective LNG plasma level of 0.2 ng/ml was 168 days. By comparison, a similar dose of LNG microcrystals used as control produced a much higher plasma level of 15–21 ng/ml in the first day followed by a fast and continuous decline of LNG levels with a duration of only about 35 days.
Keywords: Levonorgestrel; Poly(d,l-lactide-co-glycolide); Microspheres; In vitro release; In vivo release; Rats;
Release characteristics of anionic drug compounds from liquid crystalline gels by Dara Fitzpatrick; John Corish (226-236).
Liquid crystalline gels (LCG) offer the formulator dynamic and flexible vehicles, into which actives, enhancers and other adjuvants with a wide range of physicochemical properties can be incorporated. This is achievable because of the biphasic oil/water composition of the gel. In this paper, the suitability of an isotropic liquid crystalline gel is investigated for a range of anionic drug molecules, with particular emphasis on sodium diclofenac. Parameters, which have been investigated, include the mode of vehicle preparation, the effect of the concentration of the drug and how buffering the gel and/or the receptor medium affect the release profiles. Such profiles have been measured for the sodium salts of benzoate, salicylate and indomethacin. The passive release from the standard system was found to adhere to matrix-controlled diffusion. An increase in concentration leads to a non-linear increase in the cumulative release of sodium diclofenac from the gels. In direct contrast to the result reported for cationic salbutamol base, optimum release from the gel was achieved when neither the receptor medium nor the aqueous phase of the gel was buffered. The percentages released of the sodium salts of benzoate, salicylate and indomethacin, after 24 h, were determined to be 25, 26 and 19%, respectively, and these are significantly greater than the release of sodium diclofenac. This suggests that diclofenac undergoes ion-pairing or complexation within the gel, which inhibits its diffusion from the vehicle. Future papers will report on the incorporation of enhancers and the effects of iontophoresis on the release profiles of drugs from these gels, and ultimately on the transdermal transport of drugs from these vehicles across human and porcine skin.
Keywords: Diclofenac; Liquid crystalline gel; Transdermal; Buffering; Vehicle preparation;
Phase behavior of the microemulsions and the stability of the chloramphenicol in the microemulsion-based ocular drug delivery system by Feng-Feng Lv; Li-Qiang Zheng; Chen-Ho Tung (237-246).
Microemulsion systems composed of Span20/80 + Tween20/80 + n-butanol + H2O + isopropyl palmitate (IPP)/isopropyl myristate (IPM) were investigated as model systems of drug carriers for eye drops. Effects of chloramphenicol, normal saline, sodium hyaluronate and various oils on the phase behavior were studied. The phase transition was investigated by the electrical conductivity measurements. The electrical conductivity of the microemulsion was affected by the encapsulation of the drug into the system, and the addition of normal saline and sodium hyaluronate. The chloramphenicol is used to treat the diseases such as trachoma and keratitis. However, this drug in the common eye drops hydrolyzes easily. The main product of the hydrolysis is glycols. Here, the chloramphenicol was trapped into the oil-in-water (o/w) microemulsions and its stability was investigated by the high performance liquid chromatography (HPLC) assays in the accelerated experiments of 3 months. Its location in the microemulsion formulations was determined by means of 1H NMR spectroscopy. The results of HPLC revealed that the contents of the glycols in the microemulsion formulations were much lower than that in the commercial eye drops at the end of the accelerated experiments. It implied that the stability of the chloramphenicol in the microemulsion formulations was increased remarkably. The NMR experiments confirmed that the chloramphenicol molecules should be trapped into the hydrophilic shells of the microemulsion drops, which was composed of many oxyethylene groups. The nitro-groups of the chloramphenicol molecules were near the α2-CH2 of the surfactant molecules and the benzene rings of the chloramphenicol molecules were near the oxyethylene groups of the surfactant molecules. It was this reason that enabled the chloramphenicol molecules in the microemulsions to be screened from the bulk water and its stability to be increased remarkably.
Keywords: Microemulsion; Chloramphenicol eye drops; Phase behavior; Electrical conductivity; Stability;
Encapsulation of lipopeptides within liposomes: Effect of number of lipid chains, chain length and method of liposome preparation by Ming T. Liang; Nigel M. Davies; Istvan Toth (247-254).
The purpose of this study was to systematically investigate the effect of lipid chain length and number of lipid chains present on lipopeptides on their ability to be incorporated within liposomes. The peptide KAVYNFATM was synthesized and conjugated to lipoamino acids having acyl chain lengths of C8, C12 and C16. The C12 construct was also prepared in the monomeric, dimeric and trimeric form. Liposomes were prepared by two techniques: hydration of dried lipid films (Bangham method) and hydration of freeze-dried monophase systems. Encapsulation of lipopeptide within liposomes prepared by hydration of dried lipid films was incomplete in all cases ranging from an entrapment efficiency of 70% for monomeric lipoamino acids at a 5% (w/w) loading to less than 20% for di- and trimeric forms at loadings of 20% (w/w). The incomplete entrapment of lipopeptides within liposomes appeared to be a result of the different solubilities of the lipopeptide and the phospholipids in the solvent used for the preparation of the lipid film. In contrast, encapsulation of lipopeptide within liposomes prepared by hydration of freeze-dried monophase systems was high, even up to a loading of 20% (w/w) and was much less affected by the acyl chain length and number than when liposomes were prepared by hydration of dried lipid films. Freeze drying of monophase systems is better at maintaining a molecular dispersion of the lipopeptide within the solid phospholipid matrix compared to preparation of lipid film by evaporation, particularly if the solubility of the lipopeptide in solvents is markedly different from that of the polar lipids used for liposome preparation. Consequently, upon hydration, the lipopeptide is more efficiently intercalated within the phospholipid bilayers.
Keywords: Liposomes; Lipopeptides; Lipoamino acid conjugates; Sub-unit vaccines;
Uptake characteristics of galactosylated emulsion by HepG2 hepatoma cells by Chittima Managit; Shigeru Kawakami; Fumiyoshi Yamashita; Mitsuru Hashida (255-261).
Galactosylated (Gal) emulsions containing various molar ratios of cholesten-5-yloxy-N-(4-((1-imino-2-d-thiogalactosylethyl)amino)butyl)formamide (Gal-C4-Chol) as a ligand for asialoglycoprotein receptors were prepared to study the effect of the galactose content of Gal-emulsions labeled with [3H]cholesteryl hexadecyl ether on their targeted delivery to hepatocytes. The uptake characteristics of Gal-emulsions having Gal-C4-Chol of 1, 3, 4, 6, and 9 mol% were evaluated in HepG2 cells which posses asialoglycoprotein receptors and NIH3T3 cells which are lack of asialoglycoprotein receptors. The uptake and internalization by HepG2 cells was enhanced by the addition of Gal-C4-Chol to the Gal-emulsions whereas the uptake of Gal-emulsions by NIH3T3 cells was not much and was comparable with that of bare-emulsions. In the presence of excess Gal-BSA, the uptake of Gal-emulsions having Gal-C4-Chol of 4, 6, and 9% was inhibited suggesting asialoglycoprotein receptor mediated uptake. Moreover, Gal-emulsions having Gal-C4-Chol of 4, 6, and 9% showed a slight increase in surface binding and exhibited extensive uptake and internalization into HepG2 cells. The present study strongly suggested that the Gal-emulsions are taken up by the asialoglycoprotein receptor-mediated endocytosis and galactose density of Gal-emulsions is important for effective recognition and cell internalization.
Keywords: Galactosylated emulsion; Drug delivery system; Targeting; Hepatocytes;
Stability of dexamethasone sodium phosphate in rat plasma by Mahesh N. Samtani; William J. Jusko (262-266).
The use of corticosteroid prodrugs in pharmacokinetic studies poses the risk of overestimation of corticosteroid concentrations due to in vitro hydrolysis of prodrugs after sample collection. This study tests the effectiveness of the anticoagulant EDTA as a stabilizer for dexamethasone sodium phosphate (DSP) in rat plasma and provides simultaneous HPLC analysis of DSP and dexamethasone. An already developed ion-paired reversed-phase HPLC assay for simultaneous measurement of corticosteroid phosphate ester prodrugs and their active steroids was applied in this study. This assay was used for analyzing samples from an in vitro DSP hydrolysis study in rat plasma. In agreement with allometric principles, the prodrug hydrolysis occurred at a much faster rate (in vitro half-life of 1.75 h) in rat plasma as compared with previously reported prodrug hydrolysis half-life of 10–12 h in sheep and human plasma. The in vitro degradation of the prodrug in rat plasma was greatly minimized in plasma containing EDTA at the concentration commonly used an anticoagulant. This study demonstrates that artifacts in pharmacokinetic profiles of corticosteroids due to in vitro prodrug hydrolysis can be greatly minimized by collecting blood samples with EDTA as the anticoagulant.
Keywords: Corticosteroid; EDTA; HPLC; Pharmacokinetics; Prodrug; Stability in plasma;
by Kevin M.G. Taylor (267).
Nano-encapsulation of azole antifungals: Potential applications to improve oral drug delivery by Rajesh Pandey; Zahoor Ahmad; Sadhna Sharma; G.K. Khuller (268-276).
The present study was designed to improve the oral bioavailability of two clinically important antifungal drugs—clotrimazole and econazole. Each drug was encapsulated in nanoparticles of a synthetic polymer (polylactide-co-glycolide, PLG) or a natural polymer (alginate stabilized with chitosan). The nanoparticles were prepared by the emulsion–solvent-evaporation technique in case of PLG and by the cation-induced controlled gelification in case of alginate. Drug encapsulation efficiency was better (>90%) for the alginate formulation compared with the PLG formulation (nearly 50%). The formulations were orally administered to mice and the drugs were analyzed in plasma by a validated HPLC technique. The biodistribution/pharmacokinetic data suggested that there was a controlled drug release for 5–6 days with each of the formulations, compared with unencapsulated drugs, which were cleared within 3–4 h of oral/intravenous administration. There was a striking improvement in the relative and absolute bioavailability of each drug. Further, the drugs were detected in the tissues (lungs, liver and spleen) till 6–8 days in case of nanoparticles whereas free drugs were cleared by 12 h. Overall, the alginate formulation appeared to be better than the PLG formulation. The results emphasize the power of nanotechnology to make the concept of enhancement in oral bioavailability of azole antifungal drugs come to reality.
Keywords: Nanoparticles; Clotrimazole; Econazole; Polylactide-co-glycolide; Alginate;
A multifunctional envelope-type nano device for novel gene delivery of siRNA plasmids by Rumiko Moriguchi; Kentaro Kogure; Hidetaka Akita; Shiroh Futaki; Makoto Miyagishi; Kazunari Taira; Hideyoshi Harashima (277-285).
A multifunctional envelope-type nano device (MEND) for use in the delivery of siRNA expression plasmids is described. The plasmid DNA encoding anti-luciferase short interfering RNA (siRNA) was condensed by poly-l-lysine (PLL) and packaged into the MEND. The silencing effect of the MEND(PLL) showed a 96% inhibition of luciferase activities in a co-transfection study. The silencing effect was maintained at more than 60%, even under the 100-fold diluted conditions. In the luciferase transformed cells, however, the MEND(PLL) showed no significant silencing effect (10%), indicating heterogeneity in transfection by the MEND(PLL). To solve this problem, the DNA condensing agents were optimized by comparing PLL, stearyl octaarginine (STR-R8) and protamine (Prot). No difference in silencing effect (95–97%) was found among these MENDs in a co-transfection study. However, the MEND(Prot) showed a 70% silencing effect in the transformed cells. These results suggest that the MEND(Prot) has less heterogeneity in transfection, while the MEND(PLL) and the MEND(STR-R8) have large heterogeneities. These results demonstrate that MEND(Prot) is a promising gene delivery system for siRNA expression plasmids with less heterogeneity associated with the transfection.
Keywords: Non-viral gene delivery system; Multifunctional envelope-type nano device; siRNA plasmid; Protamine;
Preparation and characterization of uniform nanosized cephradine by combination of reactive precipitation and liquid anti-solvent precipitation under high gravity environment by Jie Zhong; Zhigang Shen; Yan Yang; Jianfeng Chen (286-293).
In this work, a novel direct method, which was combined with reactive precipitation and liquid anti-solvent precipitation under high gravity environment, had been developed to prepare nanosized cephradine with narrow particle size distribution. Compared with commercial crude cephradine, the prepared cephradine showed a significant decrease in particle size, a significant increase in the specific surface area and shorter dissolving time when used for injection. The characteristic particle size was between 200–400 nm. The specific surface area increased from 2.95 to 10.87 m2/g after micronization. When the amount of l-arginin decreased from 0.25 to 0.18 g, the mixture of nanosized cephradine and l-arginine could still dissolve in 1 min. The X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analysis indicated that the physical characteristics and molecular states remained unchanged after the recrystallization process. This method had potential application in industrial fields because of its low cost, efficient processing and the ease of scaling-up.
Keywords: Nanosized pharmaceuticals; Cephradine; Reactive precipitation; Liquid anti-solvent precipitation; Dissolving time;
In vitro degradation of polyanhydride/polyester core-shell double-wall microspheres by Emily J. Pollauf; Cory Berkland; Kyekyoon (Kevin) Kim; Daniel W. Pack (294-303).
Double-wall microspheres (DWMS), comprising distinct polymer core and shell phases, are useful and interesting for controlled-release drug delivery. In particular, the presence of a surface-eroding polymer core may be expected to limit water penetration and, therefore, delay degradation of the core phase and drug release. In this study, solid microspheres and DWMS were fabricated using a surface-eroding polymer (poly[1,6-bis(p-carboxyphenoxy)hexane]; PCPH) and a bulk-eroding polymer (poly(d,l-lactide-co-glycolide); PLG). Erosion of the particles was observed by optical and electron microscopy, while polymer degradation was followed by gel permeation chromatography, during incubation in buffer at 37 °C. Degradation and erosion were very different depending on which polymer formed the particle shell. Nevertheless, the relatively thin (∼5 μm) PCPH shells could not prevent water penetration, and the PLG cores completely eroded by 6 weeks of incubation.
Keywords: Microsphere; Double-wall microsphere; Poly(d,l-lactide-co-glycolide); Polyanhydride; Degradation;