Current Drug Delivery (v.12, #2)

Meet Our Editorial Board Member: by Istvan Toth (121-121).

Physical Means of Stratum Corneum Barrier Manipulation to Enhance Transdermal Drug Delivery by Rabinarayan Parhi, Podilam Suresh, Suhasini Patnaik (122-138).
Since the approval of first transdermal patch (Transderm Scop®) containing scopolamine in 1979, the improvement in systemic drug delivery through skin remains incremental. The traditional methods based on passive diffusion of drug molecules in to the skin are unable to deliver macromolecules, such as peptides, proteins, DNA and vaccines, due to the barrier properties of stratum corneum (SC). During the course of approximately 35 years, the focuses are not only to overcome the above barrier property of the skin but also the safety, accuracy and patient compliance aspect of the traditional methods. The former limitation can be overcome by altering the SC barrier function by different active methods such electrically assisted methods (sonophoresis, iontophoresis, electroporation, magnetophoresis, pressure waves, electron beam irradiation), SC abruption (microneedles, high-velocity jet) and SC removal (tape-stripping, suction, microdermabrasion, ablation). This review summarizes basic principles, mechanisms, advantages, limitations and recent development of above physical techniques along with skin anatomy and drug transport pathways across skin.

Mucoadhesion can be defined as adhesion in biological setting. Process of mucoadhesion takes place in 3 stages- the first stage being that of wetting or swelling of mucoadhesive polymer. Second stage involves interpenetration of the chains of mucoadhesive polymer and the third stage involves formation of chemical bonds between entangled chains. Several polymer related factors like molecular weight, chain length, degree of cross-linking, hydration, functional groups, charge, polymer concentration and several environmental and physiological factors like contact time, mucin turnover rate and mucus viscosity affect the degree of mucoadhesion. Formulation scientists have structured and engineered several mucoadhesive polymers for their usefulness in enhancement of bioavailability, controlled and targeted drug delivery. Mucoadhesive polymers can be classified as non-specific first generation polymers and novel second generation polymers based on the mechanism of mucoadhesion. Mucoadhesive drug delivery systems have been applied to buccal cavity, oesophagus, gastrointestinal tract, eye, nasal cavity, vagina and rectal cavity. Several in vitro/ex vivo and in vivo evaluation techniques have evolved for the evaluation of mucoadhesive strength of these polymers. This review provides historical perspective on mucoadhesive polymers and an understanding of the phenomenon of mucoadhesion, factors affecting mucoadhesion, types of mucoadhesive polymers, their practical applications and the various evaluation techniques for determination of mucoadhesive strength.

Studies with Emulsion Containing trans-resveratrol: in vitro Release Profile and ex vivo Human Skin Permeation by Priscila Aparecida de Almeida, Michele Campos Alves, Hudson Caetano Polonini, Stephane Lima Calixto, Tiago Brum Braga Gomes, Alexandre Augusto Barros Lataliza, Cristiano Dias da Silveira Ramos, Nadia Rezende Barbosa Raposo, Anderson de Oliveira Ferreira, Marcos Antonio Fernandes Brandao (157-165).
Resveratrol is a phenolic compound that has been widely studied in the last years because of its extensive pharmacological properties. It also has physicochemical properties that are adequate for diffusion through the human skin. An analytical method by high performance liquid chromatography was developed and validated for its determination in transdermal emulsion, as well in receptor media and skin layers. The trans-resveratrol release kinetic followed the Higushi's model (R2 = 0.9926) with steady-state diffusion flux and lag time of 138.5 µg cm–2 h–1 and 0.49 h, respectively. It showed a percentage at 64.96 % for permeation. Thus, the results suggest that the emulsion studied is a potential vehicle for transresveratrol administration by transdermal route.

Self-Emulsifying Lipid Formulation: An Overview by Vikrant Saluja, Sunnia Arora, Suman Goyal (166-176).
An important step in oral drug development is to identify drug candidates that show sufficient aqueous solubility and could resist or bypass first-pass metabolism in order to overcome bioavailability problems. Aqueous solubility is characteristically low for Biopharmaceutical Classification System (BCS) class II and class IV drug candidates. Several formulation approaches are being identified to overcome the low solubility aspect of a drug candidate such as particle size manipulation, solid dispersions, inclusion complexes and several of nanoparticle-based options. However, the formulation for drug candidates that in addition to low aqueous solubility shows high intestinal and first-pass metabolism is challenging. The self-emulsifying lipid formulations (SELF) provide a mean for sidestepping these factors and improve the bioavailability of lipophilic and highly first- pass metabolised drugs. Nevertheless, formulation of a successful SELF requires an exhaustive understanding of the component used to formulate them, the behaviour of the formulation within the gastrointestinal (GI) milieu and the mechanism by which the drug is released and absorbed. This review gives a brief description of the formulation aspects of SELF and their potential role to mitigate the bioavailability problem related to lipophilic and highly first- pass metabolised drugs.

Nanomedicines Based Drug Delivery Systems for Anti-Cancer Targeting and Treatment by Vikas Jain, Shikha Jain, S.C. Mahajan (177-191).
Cancer is defined as an uncontrolled growth of abnormal cells. Current treatment strategies for cancer include combination of radiation, chemotherapy and surgery. The long-term use of conventional drug delivery systems for cancer chemotherapy leads to fatal damage of normal proliferate cells and this is particularly used for the management of solid tumors, where utmost tumor cells are not invaded quickly. A targeted drug delivery system (TDDS) is a system, which releases the drug at a preselected biosite in a controlled manner. Nanotechnology based delivery systems are making a significant impact on cancer treatment and the polymers play key role in the development of nanopraticlulate carriers for cancer therapy. Some important technological advantages of nanotherapeutic drug delivery systems (NDDS) include prolonged half-life, improved bio-distribution, increased circulation time of the drug, controlled and sustained release of the drug, versatility of route of administration, increased intercellular concentration of drug and many more. This review covers the current research on polymer based anticancer agents, the rationale for development of these polymer therapeutical systems and discusses the benefits and challenges of cancer nanomedicines including polymer-drug conjugates, micelles, dendrimers, immunoconjugates, liposomes, nanoparticles.

Stability Studies on Piroxicam Encapsulated Niosomes by Zehra Ceren Ertekin, Zerrin Sezgin Bayindir, Nilufer Yuksel (192-199).
Drug delivery systems which yield ideal treatments are currently the center of interest for researchers. Niosomes have numerous advantages over other drug delivery systems. However, stability issue is not clear yet and is a serious drawback for niosomes. In this study, the stability of niosomes was the center of interest. Piroxicam which was chosen as the model drug was loaded to niosomes. Niosomes were prepared by thin-film method and different forms (aqueous dispersion, lyophilized powder and lyophilized powder with cryoprotectant) of the original niosome formulation were prepared. The samples were stored either at 5A°CA±3A°C or 25A°CA±2A°C/60% RHA±5% RH for 3 months. The drug leakage percent, particle size and distribution, zeta potential, drug release profiles were determined and niosomes were visualized under optic microscope. Niosome formulation provided sustained release of piroxicam. The drug leakage from stored niosomes was observed at the level of 1.56-6.63 %. Individual vesicle images were obtained for all samples by optical microscope. However, particle size of niosomes was increased upon storage. The zeta potential values were neither related to time nor physical form. Drug release profiles and amounts were quite similar for all forms of niosomes and the original formulation but a slight decrease was noticed on drug release amounts by time. This indicates that niosomes become more rigid by time. Although the ideal storage was obtained with lyophilized niosomes at 5A±3A°C in this study, the usage of suitable cryoprotectant and optimized lyophilization process should be further evaluated.

Development Of Etofenamate-Loaded Semisolid Sln Dispersions And Evaluation Of Anti-Inflammatory Activity For Topical Application by Ulya Badilli, C. Tuba Sengel-Turk, Arzu Onay-Besikci, Nilufer Tarimci (200-209).
Dermal application of various active substances is widely preferred for topical or systemic delivery. SLNs consist of biocompatible and non-toxic lipids and have a great potential for topical application in drugs. In this study, semisolid SLN formulations were successfully prepared by a novel one-step production method as a topical delivery system of etofenamate, an anti-inflammatory drug. Compritol 888 ATO and Precirol ATO 5 were chosen as lipid materials for the fabrication of the formulations. In-vitro evaluation of the formulations was performed in terms of encapsulation efficiency, particle size, surface charge, thermal behavior, rheological characteristics, in vitro drug release profile, kinetics, mechanisms, stability, and anti-inflammatory activity. The colloidal size and spherical shape of the particles were proved. According to the results of the rheological analysis, it was demonstrated that the semisolid SLN formulations have a gel-like structure. Stability studies showed that semisolid SLNs were stable at 4A°C for a six month period. Zero order release was obtained with Precirol ATO 5, while Compritol 888 ATO followed the square root of time (Higuchi's pattern) dependent release. Semisolid SLNs showed higher inhibitory activity of COX in comparison with pure etofenamate. In conclusion, etofenamate-loaded semisolid SLN formulations can be successfully prepared in a novel one-step production method and useful for topical application.

Controlled Release of Insulin in Blood from Strontium-Substituted Carbonate Apatite Complexes by Aiman Ahmad, Iekhsan Othman, Anuar Zaini Md Zain, Ezharul Hoque Chowdhury (210-222).
Diabetes mellitus is a chronic disease accompanied by a multitude of problems worldwide with subcutaneously administered insulin being the most common therapy currently. Controlledrelease insulin is assumed to be of high importance for long-term glycaemic control by reducing the number of daily injections. Long-acting insulin also mimics the basal insulin levels in normal individuals that may be lacking in diabetic patients. Nanoparticles of carbonate apatite as established for efficient intracellular transport of DNA and siRNA have the potential to be used for sustained release of insulin as responsive nano-carriers. The flexibility in the synthesis of the particles over a wide range of pHs with eventual adjustment of pH-dependent particle dissolution and the manageable variability of particle-integrity by incorporating selective ions into the apatite structure are the promising features that could help in the development of sustained release formulations for insulin. In particular strontium-incorporated carbonate apatite particles were formulated and compared with those of unsubstituted apatite in the context of insulin binding and subsequent release kinetics in DMEM, simulated buffer and finally human blood over a period of 20 hours. Clearly, the former demonstated to have a stronger electrostatic affinity towards the acidic insulin molecules and facilitate to some extent sustained release of insulin by preventing the initial burst effect at physiological pH in comparison with the latter. Thus, our findings suggest that optimization of the carbonate apatite particle composition and structure would serve to design an ideal insulin nano-carrier with a controlled release profile.

Membrane-Permeabilizing Activity of Reverse-Amide 2-Aminoimidazole Antibiofilm Agents Against Acinetobacter baumannii by Sean D. Stowe, Richele J. Thompson, Lingling Peng, Zhaoming Su, Meghan S. Blackledge, G. Logan Draughn, William H. Coe, Eva Johannes, Valerie K. Lapham, John Mackenzie, Christian Melander, John Cavanagh (223-230).
Acinetobacter baumannii has quickly become one of the most insidious and prevalent nosocomial infections. Recently, the reverse-amide class of 2-aminoimidazole compounds (RA-2AI) was found both to prevent A. baumannii biofilm formation and also to disperse preexisting formations, putatively through interactions with cytosolic response regulators. Here we focus on how this class of antibiofilm agent traverses cellular membranes. Following the discovery of dosage-dependent growth rate changes, the cellular effects of RA-2AI were investigated using a combination of molecular assays and microscopic techniques. It was found that RA-2AI exposure has measureable effects on the bacterial membranes, resulting in a period of increased permeability and visible structural aberrations. Based on these results, we propose a model that describes how the structure of RA-2AI allows it to insert itself into and disrupt the fluidity of the membrane, creating an opportunity for increased molecular permeability.

Design of Sustained Release Tablet Containing Fucoidan by Thao Truong-Dinh Tran, Dai Kieu-Phuong Ngo, Toi Van Vo, Phuong Ha-Lien Tran (231-237).
The study introduced a new therapeutic agent, fucoidan, which can offer potential medical treatments including anti-inflammatory and anti-coagulant activities, as well as anti-proliferative effects on cancer cells. Fucoidan was included in sustained release formulations expected for an effective plasma drug concentration for approximately 24 h. The matrices based on the two polymers hydroxypropyl methycellulose (HPMC) and polyethylene oxide (PEO) were prepared with various ratios between the polymers and fucoidan. The dissolution profiles of various matrix tablets performed in enzyme- free simulated intestinal fluid (pH 6.8) for 24 h indicated a higher potential of PEO-based matrix tablets in sustaining release of fucoidan. The swelling and erosion of the tablets were also characterized to elucidate the difference among those dissolution profiles.

The efficiency of the human intestinal absorption (HIA) of the 59 drugs which are marketed as salts is predicted using the rule of unity. Intrinsic aqueous solubilities and partition coefficients along with the drug dose are used to calculate modified absorption potential (MAP) values. These values are shown to be related to the fraction of the dose that is absorbed upon oral administration in humans (FA). It is shown that the MAP value can distinguish between drugs that are poorly absorbed (FA <0.5) and those that are well absorbed (FA ≥ 0.5). Inspection of the data as well as a receiver operative characteristic (ROC) plot shows that a single critical MAP value can be used for predicting efficient human absorption of drugs. This forms the basis of a simple rule of unity based solely on in vitro data for predicting whether or not a drug will be well absorbed at a given dose.

Self Emulsifying Drug Delivery System (SEDDS) for Phytoconstituents: A Review by Neeraj Chouhan, Vineet Mittal, Deepak Kaushik, Anurag Khatkar, Mitali Raina (244-253).
The self emulsifying drug delivery system (SEDDS) is considered to be the novel technique for the delivery of lipophillic plant actives. The self emulsifying (SE) formulation significantly enhance the solubility and bioavailability of poorly aqueous soluble phytoconstituents. The self emulsifying drug delivery system (SEDDS) can be developed for such plant actives to enhance the oral bioavailability using different excipients (lipid, surfactant, co solvent etc.) and their concentration is selected on the basis of pre formulation studies like phase equilibrium studies, solvent capacity of oil for drug and mutual miscibility of excipients. The present review focuses mainly on the development of SEDDS and effect of excipients on oral bioavailability and aqueous solubility of poorly water soluble phytoconstituents/ derived products. A recent list of patents issued for self emulsifying herbal formulation has also been included. The research data for various self emulsifying herbal formulation and patents issued were reviewed using different databases such as PubMed, Google Scholar, Google patents, Scopus and Web of Science. In a nutshell, we can say that SEDDS was established as a novel drug delivery system for herbals and with the advances in this technique, lots of patents on herbal SEDDS can be translated into the commercial products.