Advances in Colloid and Interface Science (v.199-200, #C)

Phenothiazine drugs have been the subject of great interest due to their interesting aggregation properties and ability to interact with surfactants, model lipid bilayers, and biomembranes. Since these drugs show enormous pharmacological actions and deposits on the biomembranes, their pharmacological activities seem to be related to the drug–membrane interactions or to the absorbability on the membrane. Further, the mechanisms for the various biological activities of phenothiazines can be explained by exploring these drug–membrane interactions. Keeping these points in view, many researchers have investigated the interactions of these drugs with surfactants. This review describes the physicochemical aspects of the interactions between phenothiazine drugs and surfactants which have been discussed under three sections: (i) micellar and interfacial studies, (ii) spectroscopic studies, (iii) phase separation studies (CP) and (iv) miscellaneous.Display Omitted
Keywords: Phenothiazine drugs; Surfactants; Micellization; Interfacial; Spectroscopic; Phase separation;

Accuracy of surface tension measurement from drop shapes: The role of image analysis by Ali Kalantarian; Sameh M.I. Saad; A. Wilhelm Neumann (15-22).
Axisymmetric Drop Shape Analysis (ADSA) has been extensively used for surface tension measurement. In essence, ADSA works by matching a theoretical profile of the drop to the extracted experimental profile, taking surface tension as an adjustable parameter. Of the three main building blocks of ADSA, i.e. edge detection, the numerical integration of the Laplace equation for generating theoretical curves and the optimization procedure, only edge detection (that extracts the drop profile line from the drop image) needs extensive study. For the purpose of this article, the numerical integration of the Laplace equation for generating theoretical curves and the optimization procedure will only require a minor effort. It is the aim of this paper to investigate how far the surface tension accuracy of drop shape techniques can be pushed by fine tuning and optimizing edge detection strategies for a given drop image. Two different aspects of edge detection are pursued here: sub-pixel resolution and pixel resolution. The effect of two sub-pixel resolution strategies, i.e. spline and sigmoid, on the accuracy of surface tension measurement is investigated. It is found that the number of pixel points in the fitting procedure of the sub-pixel resolution techniques is crucial, and its value should be determined based on the contrast of the image, i.e. the gray level difference between the drop and the background. On the pixel resolution side, two suitable and reliable edge detectors, i.e. Canny and SUSAN, are explored, and the effect of user-specified parameters of the edge detector on the accuracy of surface tension measurement is scrutinized. Based on the contrast of the image, an optimum value of the user-specified parameter of the edge detector, SUSAN, is suggested. Overall, an accuracy of 0.01 mJ/m2 is achievable for the surface tension determination by careful fine tuning of edge detection algorithms.Display Omitted
Keywords: Axisymmetric Drop Shape Analysis; Surface tension; Edge detection; Sub-pixel resolution;

Drug delivery using nanoparticles as drug carriers has recently attracted the attention of many investigators. Targeted delivery of nanoparticles to the lymph nodes is especially important to prevent cancer metastasis or infection, and to diagnose disease stage. However, systemic injection of nanoparticles often results in organ toxicity because they reach and accumulate in all the lymph nodes in the body. An attractive strategy would be to deliver the drug-loaded nanoparticles to a subset of draining lymph nodes corresponding to a specific site or organ to minimize systemic toxicity. In this respect, mucosal delivery of nanoparticles to regional draining lymph nodes of a selected site creates a new opportunity to accomplish this task with minimal toxicity. One example is the delivery of nanoparticles from the vaginal lumen to draining lymph nodes to prevent the transmission of HIV in women. Other known examples include mucosal delivery of vaccines to induce immunity. In all cases, molecular and particle transport by means of diffusion and convective diffusion play a major role. The corresponding transport processes have common inherent regularities and are addressed in this review. Here we use nanoparticle delivery from the vaginal lumen to the lymph nodes as an example to address the many aspects of associated transport processes. In this case, nanoparticles penetrate the epithelial barrier and move through the interstitium (tissue) to the initial lymphatics until they finally reach the lymph nodes.Since the movement of interstitial liquid near the epithelial barrier is retarded, nanoparticle transport was found to take place through special foci present in the epithelium. Immediately after nanoparticles emerge from the foci, they move through the interstitium due to diffusion affected by convection (convective diffusion). Specifically, the convective transport of nanoparticles occurs due to their convection together with interstitial fluid through the interstitium toward the initial lymph capillaries. Afterwards, nanoparticles move together with the lymph flow along the initial lymph capillaries and then enter the afferent lymphatics and ultimately reach the lymph node. As the liquid moves through the interstitium toward the initial lymph capillaries due to the axial movement of lymph along the lymphatics, the theory for coupling between lymph flow and concomitant flow through the interstitium is developed to describe this general case.The developed theory is applied to interpret the large uptake of Qdots by lymph nodes during inflammation, which is induced by pre-treating mouse vagina with the surfactant Nonoxynol-9 prior to instilling the Qdots. Inflammation is viewed here to cause broadening of the pores within the interstitium with the concomitant formation of transport channels which function as conduits to transport the nanoparticles to the initial lymph capillaries. We introduced the term “effective channels” to denote those channels which interconnect with foci present in the epithelial barrier and which function to transport nanoparticles to initial lymph capillaries. The time of transport toward the lymph node, predicated by the theory, increases rapidly with increasing the distance y 0 between the epithelial barrier and the initial lymph capillaries. Transport time is only a few hours, when y 0 is small, about some R (where R is the initial lymph capillary radius), due to the predomination of a rather rapid convection in this case. This transport time to the lymph nodes may be tens of hours (or longer) when y 0 is essentially larger and the slow diffusion controls the transport rate in a zone not far from the epithelial barrier, where convection is weak at large y 0. Accounting for transport by diffusion only, which is mainly considered in many relevant publications, is not sufficient to explain our nanoparticle uptake kinetics because the possibility of fast transport due to convection is overlooked. Our systematic investigations have revealed that the information about the main transport conditions, namely, y 0 and the pore broadening up to the dimension of the interstitial transport channels, is necessary to create the quantitative model of enhanced transport during inflammation with the use of the proposed model as a prerequisite.The modeling for convective diffusion of nanoparticles from the epithelial barrier to the lymph node has been mainly accomplished here, while the diffusion only scenario is accounted for in other studies. This first modeling is a semi-quantitative one. A more rigorous mathematical approach is almost impossible at this stage because the transport properties of the model are introduced here for the first time. These properties include: discovery of foci in the epithelium, formation of transport channels, definition of channels interconnecting with foci (effective foci and channels), generation of flow in the interstitium toward the initial lymph capillaries due to axial flow within afferent lymphatics, deformation of this flow due to hydrodynamic impermeability of the squamous layer with the formation of the hydrodynamic stagnation zone near the epithelial barrier, predomination of slow diffusion transport within the above zone, and predomination of fast convection of nanoparticles near the initial lymph capillaries.Display Omitted
Keywords: Convective diffusion; Interstitium hydrodynamics; Interstitium channels; Effective channels; Foci; Effective foci; Epithelial barrier defects; Lymphatic vaccine delivery; Therapeutic nanoparticles; Quantum dots; HIV prevention;

Gold nanoparticles: A paradigm shift in biomedical applications by Mohammed S. Khan; Gowda D. Vishakante; Siddaramaiah H (44-58).
In the medical field, majority of the active ingredients exists in the form of solid particle (90% of all medicines). Nanotechnology had grabbed the attention of many scientists working in different aspects and gave them a vivid imagination in order to utilize the nanotechnology in an innovative way according to their needs. One of the major applications of nanotechnology is drug delivery through nanoparticles which is on boom for the researchers and gives a challenging environment for the researchers. Among them upcoming challenge is the use of inorganic nanoparticles for the drug delivery and related aspects. There is growing interests in usage of inorganic nanoparticles in medicine due to their size, and unique physical properties that make them different from other nanoparticulate systems. This review will lay special emphasis on the uniqueness of inorganic nanoparticles especially gold nanoparticles as a drug delivery vehicle and moreover will present a wide spread scenario of gold nanoparticles that has been used for treatment of life threatening diseases like cancer.Nanomaterials have recently attracted strong interest from the scientific community all over the world not only as budding drug delivery vehicles, but also as diagnostic tools, as a radio contrast agent in cancer therapy and as biomarkers in molecular deep tissue imaging techniques. This review mainly focuses on gold nanoparticles and discusses the role of gold nanoparticle in drug delivery, including their synthesis, chemical modifications, properties and their usage as biomarkers in the pharmaceutical field. The review focuses on the recent contribution of gold nanoparticles in the medical field.Display Omitted
Keywords: Gold nanoparticles; Cancer therapy; Computed tomography; Biomedical applications;

Charged aerosol detection to characterize components of dispersed-phase formulations by Christopher B. Fox; Sandra J. Sivananthan; Traci J.T. Mikasa; Susan Lin; Sarah C. Parker (59-65).
Colloidal formulations based on biocompatible phospholipids, emulsifiers, and oils are employed in a wide range of applications including medicine, food, and cosmetics. However, characterization of these dispersed-phase components may be difficult to analyze by traditional HPLC with UV, visible, or fluorescence detection modalities due to lack of chromophores or fluorophores. Charged aerosol detection (CAD) is increasingly used for analysis of dispersed-phase components due to its broad applicability and high sensitivity for non-chromophore containing components found in many colloidal systems, such as lipid-based molecules. In this review, we summarize the recent applications of CAD reported in the literature as well as our own laboratory for the analysis of widely used components of dispersed-phase systems. In particular, we discuss the advantages and disadvantages of CAD compared to other HPLC detection methods, as well as the various sample preparation methods suitable for colloidal formulations prior to HPLC–CAD analysis.Display Omitted
Keywords: Charged aerosol detection; Emulsions; Vaccine adjuvants; Liposomes; Saponins;

We illustrate the great potential of Raman and ROA spectroscopies for investigating the structure and organisation of glycoproteins and the complex matrices they can form. In combination these spectroscopic techniques are sensitive to changes in conformation revealing details of secondary and tertiary structures, probing hydrogen bonding interactions, as well as resolving side chain orientation and the absolute configuration of chiral substructures. To demonstrate this potential we have characterised the structural changes in a complex glycoprotein, mucin. Spectral changes were observed during the entanglement transition as the mucin concentration was increased. By applying two-dimensional correlation analysis (2DCos) to the ROA and Raman concentration-dependent spectral sets delicate transitions in mucin conformation could also be determined. From ~ 20–40 mg/ml conformational transitions assigned mainly to the sugar N-acetyl-d-galactosamine (GalNAc), which is the linking saccharide unit to the protein backbone, were monitored. Further changes in local oligosaccharide conformation above 40 mg/ml were also monitored, together with other structural transitions observed in the protein core, particularly β-structure formation. Consequently, these spectral techniques were shown to monitor the formation of transient entanglements formed by brush–brush interactions between oligosaccharide combs of mucin molecules identifying changes in both carbohydrate and protein moieties. This work clearly shows how these methods can be used to elucidate fresh insights into the complex behaviour of these large complex molecules.Display Omitted
Keywords: Raman optical activity; Raman spectroscopy; Glycoprotein; Mucin; Polymer entanglement; 2D correlation analysis;

Modeling and simulation of electrostatically gated nanochannels by G. Pardon; W. van der Wijngaart (78-94).
Today, despite the growing interest in nanofluidics, the descriptions of the many complex physical phenomena occurring at this scale remain scattered in the literature. Due to the additional complexity encountered when considering electrostatic nanofluidic gating, it is important to regroup several relevant theories and discuss them with regard to this application. In this work, we present a theoretical study of electrostatically gated phenomena and propose a model for the electrostatic gating of ion and molecular transport in nanochannels. In addition to the classical electrokinetic equations, that are reviewed in this work, several relevant phenomena are considered and combined to describe gating effects on nanofluidic properties more accurately. Dynamic surface charging is accounted for and is shown to be an essential element for electrostatic gating. The autoprotolysis of water is also considered to allow for accurate computing of the surface charge. Modifications of the Nernst–Planck equations are considered for more accurate computing of the concentration profiles at higher surface potentials by accounting for ion crowding near charge walls. The sensitivity of several parameters to the electric field and ion crowding is also studied. Each of these models is described separately before their implementation in a finite element model. The model is verified against previous experimental work. Finally, the model is used to simulate the tuning of the ionic current through the nanochannel via electrostatic gating. The influence of the additional models on these results is discussed. Guidelines for potentially better gating efficiencies are finally proposed.Display Omitted
Keywords: Nanofluidics; Electrostatic gating; Nanofluidic transistor; Model; Nanochannel;

Superparamagnetic iron oxide based nanoprobes for imaging and theranostics by Tina Lam; Philippe Pouliot; Pramod K. Avti; Frédéric Lesage; Ashok K. Kakkar (95-113).
The need to target, deliver and subsequently evaluate the efficacy of therapeutics in the treatment of a disease has provided added impetus in developing novel and highly efficient contrast agents. Superparamagnetic iron oxide nanoparticles (SPIONs) have offered tremendous potential in designing advanced magnetic resonance imaging (MRI) diagnostic agents, due to their unique physicochemical properties. There has been tremendous effort devoted in the recent past in developing synthetic methodologies through which their size, hydrodynamic radii, chemical composition and morphologies could be tailored at the nanoscale. This enables one to fine tune their magnetic behavior, and thus their MRI response. While novel synthetic strategies are being assembled for directing SPIONs to the diseased site as well as imparting them stealth and biocompatibility, it is also essential to evaluate their biological toxicological profiles. This review highlights recent advances that have been made in the synthesis of SPIONs, subsequent functionalization with desired entities, and a discussion on their use as MRI contrast agents in cardiovascular research.Display Omitted
Keywords: Superparamagnetic iron oxide nanoparticles (SPIONs); Magnetic resonance imaging (MRI); Cardiovascular disease; Synthesis; Physicochemical properties;

A particle gel is a network of aggregated colloidal particles with soft solid-like mechanical properties. Its structural and rheological properties, and the kinetics of its formation, are dependent on the sizes and shapes of the constituent particles, the volume fraction of the particles, and the nature of the interactions between the particles before, during and after gelation. Particle gels may be permanent or transient depending on whether the colloidal forces between the aggregating particles lead to irreversible bonding or weak reversible interactions. With short-range reversible interactions, network formation is typically associated with phase separation or kinetic arrest due to particle crowding. Much existing knowledge has been derived from computer simulations of idealized model systems containing spherical particles interacting with well-defined pair potentials. The status of current progress is reviewed here by summarizing the underlying methodology and key findings from a range of simulation approaches: Monte Carlo, molecular dynamics, Brownian dynamics, Stokesian dynamics, dissipative particle dynamics, multiparticle collision dynamics, and fluid particle dynamics. Then it is described how the technique of Brownian dynamics simulation, in particular, has provided detailed insight into how different kinds of bonding and weak reversible interactions can affect the aggregate fractal structure, the percolation behaviour, and the small-deformation rheological properties of network-forming colloidal systems. A significant ongoing development has been the establishment and testing of efficient algorithms that are able to capture the subtle dynamic structuring effects that arise from effects of interparticle hydrodynamic interactions. This has led to an appreciation recently of the potentially important role of these particle–particle hydrodynamic effects in controlling the evolving morphology of simulated colloidal aggregates and in defining the location of the sol–gel phase boundary.Display Omitted
Keywords: Computer simulation; Particle gelation; Aggregation; Percolation; Brownian dynamics; Hydrodynamics; Fractal structure; Rheology;