Preparation and evaluation of functional allopurinol imprinted starch based biomaterials for transdermal drug delivery.

This study focuses on the synthesis of functional allopurinol (ALP) imprinted biomaterials for a transdermal drug delivery using mung bean starch (MBS), polyvinyl alcohol (PVA), sodium benzoate (SB) as a crosslinking agent, and poloxamer (PX) as a thermo-sensitive polymer. Prepared functional biomaterials were characterized and evaluated by SEM, FT-IR analysis, and physical properties. Results of ALP recognition properties indicated that adsorbed amounts (Q) of ALP on functional ALP imprinted biomaterials were 3.8 to 4.9-fold higher than that of non-ALP imprinted biomaterial. Results of ALP release revealed that the ALP release rate for PX added biomaterials was 1.10 (36.5 °C) or 1.30 (45 °C) times faster than that at 25 °C. These results indicate that functional ALP imprinted biomaterials have thermo-sensitive properties due to the addition of PX. Results of ALP release using artificial skin indicated that ALP release was increased at a relatively steady-state rate for 3 h and that the ALP release behavior followed the non-Fickian diffusion mechanism.

An attempt to enhance solubility of metoclopramide base by Solid dispersion strategy and its application on development of Transdermal device

Chemotherapy induced nausea and vomiting (CINV) is an issue, which usually occurs in cancer patient. Despite high bioavailability of oral and intravenous administration, these have some drawbacks. The oral route causes hepatic first pass metabolism and intravenous route is invasive in nature. Hence, antiemetic drug by means of transdermal route is necessary to administer in such cases. The aim of the present investigation is to develop suitable Transdermal Therapeutic System (TTS) with an objective to enhance solubility and skin permeability properties of metoclopramide base. Preformulation study begins with an approach to enhance solubility of 40 metoclopramide base by solid dispersion technique. transdermal films were prepared with 41 the solid dispersion as well as with pure drug. Phase solubility study at various temperatures reveals binding constants (Ka, 95-350 M-1 for PVP K30; 56-81 M-1 for HPßCD). Spontaneity of solubilization was justified by AL type linear profiles. The films showed satisfactory diffusion (%), permeation rate and flux after 8 h study. The transdermal patches as prepared were analyzed under FTIR, DSC and SEM. Both solubility and permeability rate in this investigation have been enhanced. So, it can be affirmed that this route would effectively enhance bioavailability

Effect of Common Excipients on Intestinal Drug Absorption in Wistar Rats.

The aim of the present paper is to study the effect of common excipients on the permeability of atenolol (as drug absorbed mainly by passive diffusion) and rhodamine (as P-glycoprotein substrate). The apparent permeability was measured by an in situ perfusion method in Wistar rats using the closed loop Doluisio's method. Permeability values were characterized in the absence and presence of 18 commonly used excipients. Excipient concentrations were selected based on the amounts in oral immediate release dosage forms, which failed the test during the human bioequivalence studies. Atenolol was studied with and without excipients in the whole small intestine, whereas rhodamine was tested in three different intestinal segments to account for the differential expression of P-glycoprotein, and it was further on tested in the ileum, in the presence of excipients. Atenolol presented higher permeability values when it was administered with colloidal silica, croscarmellose, hydroxypropyl methylcellulose (HPMC), magnesium stearate, MgCO3, poly(ethylene glycol) 400, poly(vinylpyrrolidone), sorbitol, starch, and TiO2 rhodamine showed higher permeability values when it was administered with croscarmellose and HPMC. On the one hand, the mechanisms of action were not discernible with the proposed experiments. On the other hand, commercial formulations do not present a single excipient but several, which can counteract their effects. The in situ perfusion technique can be useful for a preliminary screening and risk analysis, while the in vivo pharmacokinetic results would be needed to define conclusive effects.

Multiscale study on the enhancing effect and mechanism of borneolum on transdermal permeation of drugs with different log P values and molecular sizes.

D-borneolum is commonly used as a permeation enhancer in Traditional Chinese Medicine (TCM) formulas for transdermal application. Additionally, two other sources of borneolums were recorded in the 2015 edition of the Chinese Pharmacopoeia (ChP), including L-borneolum and borneolum syntheticum. To guide the selection and application of borneolum, the safety and enhancing effect of three sources of borneolums were investigated on transdermal permeation of compounds with different octanol-water partition coefficient (log P) values and molecular weights (MWs). Both the results of cellular cytotoxicity and in vitro transdermal permeation experiments showed that all three sources of borneolums could be applied in TDDS as permeation enhancers. Moreover, all three sources of borneolums achieved optimal permeation-enhancing performances on transdermal drugs with lower log P values as well as higher MWs. Further study was carried out to elucidate the potential molecular mechanism of borneolum enhancing transdermal drug delivery via transmission electron microscope (TEM) and coarse-grained molecular dynamic (CG-MD) simulation. Borneolum significantly promoted transdermal delivery of drugs via changing the dense morphology of the stratum corneum (SC), disturbing the ordered arrangement of ceramide (CER) and free fatty acid (FFA) molecules in lipid layers, and further increasing the diffusion rate of drugs in the lipid layers.

Prediction of skin permeation and concentration of rhododendrol applied as finite dose from complex cosmetic vehicles.

Finite dose experiments represent clinical use wherein depletion of dose, evaporation of excipients, and gradual change in vehicle composition may occur. In the present study, we attempted a mathematical approach for predicting skin permeation and concentration of a cosmetic active, rhododendrol (RD), from complex vehicle-based formulations applied in finite dose. In vitro skin permeation and concentration studies of RD were conducted from formulations containing water and polyols with concentrations ranging from 10 to 100% under infinite and finite dose conditions using vertical Franz diffusion cells. Observed data for skin permeation and the viable epidermis and dermis (VED) concentration of RD were estimated by the differential equations under Fick's second law of diffusion together with water evaporation kinetics and changes in the partition coefficient from vehicles to the stratum corneum. As a result, a goodness-of-fit was observed allowing accurate estimation of skin permeation and VED concentration of RD. This mathematical approach could become a useful tool to estimate the skin permeation and concentration of actives from topical formulation applied in finite dose conditions likened in actual use.

Corynebacterium pseudotuberculosis biovar ovis: evaluación de la sensibilidad antibiótica in vitro / Corynebacterium pseudotuberculosis biovar ovis: Evaluation of antibiotics susceptibility in vitro

Resumen Los objetivos de este trabajo fueron estudiar la sensibilidad antibiótica de aislamientos de Corynebacterium pseudotuberculosis procedentes de pequeños rumiantes e investigar la presencia de integrones que contienen genes de resistencia. Se estudiaron 15 aislamientos de diferentes fuentes por los métodos de difusión y dilución. Por el método de difusión, amoxicilina-clavulánico, ampicilina, cefotaxima, cefoxitina, ciprofloxacina, cloranfenicol, eritromicina, estreptomicina, gentamicina, imipenem, kanamicina, norfloxacina, penicilina, rifampicina, tetraciclina, trimetroprima-sulfametoxazol y vancomicina fueron activos frente al 100% de los aislamientos, mientras que amicacina presentó resultados variables. En los aislamientos que desarrollaron frente a amicacina se investigó la presencia de integrones de clase 1. El resultado fue negativo, sugiriendo la ausencia del integrón. Utilizando el método de dilución, los antibióticos más activos correspondieron a los grupos de cefalosporinas, gluco-péptidos, macrólidos, quinolonas y tetraciclinas. Se demostró menor actividad de p-lactámicos y aminoglucósidos. No se registró variabilidad en los perfiles antibióticos en los aislamientos procedentes de diferentes fuentes.

Abstract The aims of this work were to study the antibiotic susceptibility in Corynebacterium pseudotuberculosis isolated from small ruminants and to determine the presence of integrons that contain resistance genes. Fifteen isolates of different sources were analysed using the diffusion and the dilution methods. When the diffusion method was performed, amoxicillin-clavulanic, ampicillin, cefotaxime, cefoxitin, ciprofloxacin, chloramphenicol, erythromycin, streptomycin, gentamicin, imipenem, kanamycin, norfloxacin, penicillin, rifampicin, tetracycline, trimethoprim-sulfamethoxazole and vancomycin were effective against the 100% of isolates, while amikacin showed variable results. The isolates that were able to grow with amikacin, were studied in relation to the presence of integron class 1. The result was negative, suggesting the absence of integron. Using dilution method, the antibiotics belonging to the cephalosporin, glycopeptide, macrolide, quinolone, and tetracycline groups were the most active ones for the C. pseudotuberculosis biovar ovis isolates. Less activity of p-lactam and aminoglycosides were observed. There was no observation of variability in the antibiotic patterns in the strains coming from different sources.

Nonuniform Crowding Enhances Transport.

The cellular cytoplasm is crowded with macromolecules and other species that occupy up to 40% of the available volume. Previous studies have reported that for high crowder molecule concentrations, colloidal tracer particles have a dampened diffusion due to the higher solution viscosity. However, these studies employed uniform distributions of crowder molecules. We report a scenario, previously unexplored experimentally, of increased tracer transport driven by a nonuniform concentration of crowder macromolecules. In gradients of a polymeric crowder, tracer particles undergo transport several times higher than that of their bulk diffusion rate. The direction of the transport is toward regions of lower crowder concentration. Mechanistically, hard-sphere interactions and the resulting volume exclusion between the tracer and crowder increase the effective diffusion by inducing a convective motion of tracers, which we explain through modeling. Strikingly, soft deformable particles show even greater enhancement in transport in crowder gradients compared to similarly sized hard particles. Overall, this demonstration of enhanced transport in nonuniform distributions of crowders is anticipated to clarify aspects of multicomponent intracellular transport.

Water dynamics in MCF-7 breast cancer cells: a neutron scattering descriptive study.

Water mobility in cancer cells could be a powerful parameter to predict the progression or remission of tumors. In the present descriptive work, new insight into this concept was achieved by combining neutron scattering and thermal analyses. The results provide the first step to untangle the role played by water dynamics in breast cancer cells (MCF-7) after treatment with a chemotherapy drug. By thermal analyses, the cells were probed as micrometric reservoirs of bulk-like and confined water populations. Under this perspective we showed that the drug clearly alters the properties of the confined water. We have independently validated this idea by accessing the cellular water dynamics using inelastic neutron scattering. Finally, analysis of the quasi-elastic neutron scattering data allows us to hypothesize that, in this particular cell line, diffusion increases in the intracellular water in response to the action of the drug on the nanosecond timescale.

Impact of Molecular Crowding on Translational Mobility and Conformational Properties of Biological Macromolecules.

Effects of molecular crowding on structural and dynamical properties of biological macromolecules do depend on the concentration of crowding agents but also on the molecular mass and the structural compactness of the crowder molecules. By employing fluorescence correlation spectroscopy (FCS), we investigated the translational mobility of several biological macromolecules ranging from 17 kDa to 2.7 MDa. Polyethylene glycol and Ficoll polymers of different molecular masses were used in buffer solutions to mimic a crowded environment. The reduction in translational mobility of the biological tracer molecules was analyzed as a function of crowder volume fractions and was generally more pronounced in PEG as compared to Ficoll solutions. For several crowding conditions, we observed a molecular sieving effect, in which the diffusion coefficient of larger tracer molecules is reduced to a larger extent than predicted by the Stokes-Einstein relation. By employing a FRET-based biosensor, we also showed that a multiprotein complex is significantly compacted in the presence of macromolecular crowders. Importantly, with respect to sensor in vivo applications, ligand concentration determining sensors would need a crowding specific calibration in order to deliver correct cytosolic ligand concentration.

Dispersion in porous media in oscillatory flow between flat plates: applications to intrathecal, periarterial and paraarterial solute transport in the central nervous system.

BACKGROUND: As an alternative to advection, solute transport by shear-augmented dispersion within oscillatory cerebrospinal fluid flow was investigated in small channels representing the basement membranes located between cerebral arterial smooth muscle cells, the paraarterial space surrounding the vessel wall and in large channels modeling the spinal subarachnoid space (SSS). METHODS: Geometries were modeled as two-dimensional. Fully developed flows in the channels were modeled by the Darcy-Brinkman momentum equation and dispersion by the passive transport equation. Scaling of the enhancement of axial dispersion relative to molecular diffusion was developed for regimes of flow including quasi-steady, porous and unsteady, and for regimes of dispersion including diffusive and unsteady. RESULTS: Maximum enhancement occurs when the characteristic time for lateral dispersion is matched to the cycle period. The Darcy-Brinkman model represents the porous media as a continuous flow resistance, and also imposes no-slip boundary conditions at the walls of the channel. Consequently, predicted dispersion is always reduced relative to that of a channel without porous media, except when the flow and dispersion are both unsteady. DISCUSSION/CONCLUSIONS: In the basement membranes, flow and dispersion are both quasi-steady and enhancement of dispersion is small even if lateral dispersion is reduced by the porous media to achieve maximum enhancement. In the paraarterial space, maximum enhancement Rmax = 73,200 has the potential to be significant. In the SSS, the dispersion is unsteady and the flow is in the transition zone between porous and unsteady. Enhancement is 5.8 times that of molecular diffusion, and grows to a maximum of 1.6E+6 when lateral dispersion is increased. The maximum enhancement produces rostral transport time in agreement with experiments.

Temperature- and rigidity-mediated rapid transport of lipid nanovesicles in hydrogels.

Lipid nanovesicles are widely present as transport vehicles in living organisms and can serve as efficient drug delivery vectors. It is known that the size and surface charge of nanovesicles can affect their diffusion behaviors in biological hydrogels such as mucus. However, how temperature effects, including those of both ambient temperature and phase transition temperature (Tm), influence vehicle transport across various biological barriers outside and inside the cell remains unclear. Here, we utilize a series of liposomes with different Tm as typical models of nanovesicles to examine their diffusion behavior in vitro in biological hydrogels. We observe that the liposomes gain optimal diffusivity when their Tm is around the ambient temperature, which signals a drastic change in the nanovesicle rigidity, and that liposomes with Tm around body temperature (i.e., ∼37 °C) exhibit enhanced cellular uptake in mucus-secreting epithelium and show significant improvement in oral insulin delivery efficacy in diabetic rats compared with those with higher or lower Tm Molecular-dynamics (MD) simulations and superresolution microscopy reveal a temperature- and rigidity-mediated rapid transport mechanism in which the liposomes frequently deform into an ellipsoidal shape near the phase transition temperature during diffusion in biological hydrogels. These findings enhance our understanding of the effect of temperature and rigidity on extracellular and intracellular functions of nanovesicles such as endosomes, exosomes, and argosomes, and suggest that matching Tm to ambient temperature could be a feasible way to design highly efficient nanovesicle-based drug delivery vectors.

Illicit massive silicone injections always induce chronic and definitive silicone blood diffusion with dermatologic complications.

Male-to-female transgender (MtF TG) individuals often report using illegal subcutaneous silicone injections for body feminisation. It leads to silicone dissemination and various dermatologic complications.We report the long-term complications of these feminisation procedures with blood smear examination and dermatologic examination.Between July 2015 and December 2015, 77 MtF TG consulting at Bichat Hospital (Paris, France) were included in this cross-sectional study. Blood smear examinations were performed by a trained haematologist to quantify the presence of silicone vacuoles in monocytes.All patients reported a history of massive amounts of silicone injections (mean 4 L, range 0.5-15 L). Most patients were South American (75/77, 97%). Fifty-nine (59/75, 79%) were HIV-seropositive, mostly with undetectable HIV RNA plasma levels (46/58, 80%). Clinical examinations reported dermatologic complications for all patients: lymphatic or subcutaneous migration of silicone (59%), inflammation (50%), varicose veins (39%), post-inflammatory pigmentation (20%), infection (14%) and abscesses (4%). Blood smear examination showed intracytoplasmic vacuoles containing silicone in monocytes in all patients.We did not chemically prove the silicone nature of the vacuoles. The design of this study does not allow evaluation of short-term complications that should not be minimized.Illicit massive silicone injections always induced chronic and definitive silicone blood diffusion with dermatologic complications. This study highlights the dangers and the inefficiency of clandestine esthetic surgery. There is a need for targeted information campaigns with transgender populations about silicone injections. Otherwise, these practices may persist.

Preparation and optimization of poly (lactic acid) nanoparticles loaded with fisetin to improve anti-cancer therapy.

Fisetin is a natural flavonoid with promising antitumor activity, whereas its clinical application is limited by its hydrophobic property. In this study, we aimed to load fisetin into poly(lactic acid) (PLA) nanoparticles to increase fisetin's solubility and therapeutic efficacy. Based on spontaneous emulsification solvent diffusion (SESD) method, the formulation of PLA nanoparticles was optimized by two successive experimental designs. One-factor-at-a-time variation experiments were first applied to investigate the effects of four process variables on three responses, including drug encapsulation efficiency, average particles size and cumulative drug release ratio, followed by determining the possible ranges of these variables. Subsequently, the combinations of four variables at best levels were evaluated using a Taguchi orthogonal array design with regard to the same three responses. Eventually, the nanoparticle prepared by optimized procedure showed a narrow size distribution around 226.85 ±â€¯4.78 nm with a high encapsulation efficiency of 90.35%. The incorporation of fisetin in nanoparticles was subsequently confirmed by FT-IR and DSC spectroscopy. Furthermore, cytotoxicity assay against HCT116 colon cancer cells in vitro and antitumor test in a xenograft 4T1 breast cancer model in vivo demonstrated that the antitumor effect of drug-loaded nanoparticles was superior to that of free drug solution.

Nucleation and growth of pores in 1,2-Dimyristoyl-sn-glycero-3-phosphocholine (DMPC) / cholesterol bilayer by antimicrobial peptides melittin, its mutants and cecropin P1.

Antimicrobial peptides are one of the most promising alternatives to antibiotics for targeting pathogens without developing resistance. In this study, pore formation in 1,2-Dimyristoyl-snglycero-3-phosphocholine (DMPC) / cholesterol liposome induced by native melittin, its two mutant variants (G1I and I17 K), and cecropin P1 was investigated by monitoring the dynamics of fluorescence dye leakage. A critical peptide concentration was required for dye leakage with the rate of leakage being dependent on peptide concentration above a critical value. A lag time was required for dye leakage for low peptide concentrations that are above the critical value, which decreased at higher peptide concentrations eventually approaching zero. Lag time was found to be in the order I17 K mutant with lower hydrophobicity and higher net charge > G1I with higher hydrophobicity > melittin > cecropin P1. Cecropin P1 exhibited the highest rate of dye leakage followed by melittin, G1I, and I17 K. Size distribution and transmission electron microscopy (TEM) of liposomes exposed to peptides of different concentrations indicated pore formation with accompanied stretching of liposomes at low peptide concentrations for both melittin and cecropin P1. At much higher concentrations, however, size distribution indicated three peaks for both peptides. In both cases, TEM images show that the middle and small peaks are shown to be due to stretched liposome and broken stretched liposome respectively. For melittin, the large peak is due to peptide aggregates as well as aggregates of liposome. For cecropin P1, however, the large peak indicates cecropin P1 aggregates with solubilized lipids thus suggesting carpet mechanism.

Effect of Local Anesthetics on the Organization and Dynamics of Hippocampal Membranes: A Fluorescence Approach.

Understanding the mechanism of action of local anesthetics has been challenging. We previously showed that the local anesthetic phenylethanol (PEtOH) inhibits the function of serotonin1A receptor, which is a member of the G protein-coupled receptor family and a neurotransmitter receptor. With the objective of gaining insight into the molecular mechanism underlying the anesthetic (PEtOH) action, we monitored the organization and dynamics of hippocampal membranes using multiple fluorescent reporters, which include a molecular rotor (BODIPY-C12) and a voltage-sensitive probe (4-(2-(6-(dioctylamino)-2-naphthalenyl)ethenyl)-1-(3-sulfopropyl)-pyridinium inner salt) (di-8-ANEPPS), besides pyrene. These interfacial membrane probes were chosen because membrane partitioning of PEtOH would be reflected in the membrane interfacial environment. Taken together, we report a reduction in dipole potential and microviscosity of hippocampal membranes, with a concomitant increase in lateral diffusion in the presence of PEtOH. The reduction in membrane dipole potential induced by PEtOH constitutes one of the first experimental demonstrations on the modulation of membrane dipole potential by local anesthetics. Our results assume significance in view of previous reports that correlate membrane-perturbing effects of local anesthetics to their anesthetic action. We envision that insights into the interaction of local anesthetics with membranes could serve as a crucial link in developing a comprehensive understanding of the molecular mechanisms involved in anesthesia.

Determinants of drug-target interactions at the single cell level.

The physiochemical determinants of drug-target interactions in the microenvironment of the cell are complex and generally not defined by simple diffusion and intrinsic chemical reactivity. Non-specific interactions of drugs and macromolecules in cells are rarely considered formally in assessing pharmacodynamics. Here, we demonstrate that non-specific interactions lead to very slow incorporation kinetics of DNA binding drugs. We observe a rate of drug incorporation in cell nuclei three orders of magnitude slower than in vitro due to anomalous drug diffusion within cells. This slow diffusion, however, has an advantageous consequence: it leads to virtually irreversible binding of the drug to specific DNA targets in cells. We show that non-specific interactions drive slow drug diffusion manifesting as slow reaction front propagation. We study the effect of non-specific interactions in different cellular compartments by permeabilization of plasma and nuclear membranes in order to pinpoint differential compartment effects on variability in intracellular drug kinetics. These results provide the basis for a comprehensive model of the determinants of intracellular diffusion of small-molecule drugs, their target-seeking trajectories, and the consequences of these processes on the apparent kinetics of drug-target interactions.

The lens internal microcirculation system delivers solutes to the lens core faster than would be predicted by passive diffusion.

It has been proposed that optical properties of the lens are actively maintained by an internal microcirculation system that utilizes ionic and fluid fluxes to deliver nutrients to deeper regions of the lens tissue via the extracellular space faster than would occur by passive diffusion alone. To test this hypothesis, we utilized a range of commercially available magnetic resonance imaging (MRI) reagents of varying molecular sizes that served as tracers of extracellular solute delivery. The penetration of these tracers into bovine lenses incubated in the absence and presence of solutions that inhibit the microcirculation was monitored in real time over a 4-h period using T1-weighted MRI. We found that only the smaller contrast agents were delivered to the core of the lens and that the rate of solute penetration was significantly faster than that calculated simple diffusion. Next, the lenses were first incubated in either high extracellular K+ to depolarize the lens potential or ouabain to inhibit the Na+ pump. These two perturbations are known to inhibit the circulating ionic and fluid fluxes that are proposed to drive solute delivery into the lens core. Both perturbations inhibited the delivery of the extracellular tracer molecules to the lens core. Our findings suggest that the microcirculation system can potentially be harnessed to deliver exogenous antioxidants to the lens core to afford mature fiber cells protection against oxidative damage that ultimately manifests as age-related nuclear cataract.

Permeability of Ciprofloxacin-Loaded Polymeric Micelles Including Ginsenoside as P-glycoprotein Inhibitor through a Caco-2 Cells Monolayer as an Intestinal Absorption Model.

The low oral bioavailability of ciprofloxacin is associated with two distinct challenges: its low aqueous solubility and efflux by p-glycoproteins (P-gp) in the intestinal membrane. Several studies were conducted in order to improve its solubility and permeability through the gastrointestinal membrane. In this study, in a full factorial design study, eight polymeric micelles were prepared and their characteristics, including particle size, loading and release rate were evaluated. Polymeric micelles demonstrated particle sizes below 190 nm and 27⁻88% loading efficiency. Drug release was affected by drug solubility, polymeric micelle erosion and swelling in simulated gastrointestinal fluids. An optimized polymeric micelle was prepared based on appropriate characteristics such as high drug loading and low particle size; and was used for a permeation study on Caco-2 cells. Optimized polymeric micelles with and without ginsenoside and ginsenoside alone enhanced drug permeability through Caco-2 cells significantly in the absorptive direction. The effect of ginsenoside was dose dependent and the maximum effect was seen in 0.23 mg/mL concentration. Results showed that P-gp may not be responsible for ciprofloxacin secretion into the gut. The main mechanism of ciprofloxacin transport through Caco-2 cells in both directions is active diffusion and P-gp has inhibitory effects on ciprofloxacin permeability in the absorptive direction that was blocked by ginsenoside and micelles without ginsenoside.

Modification of sterculia gum polysaccharide via network formation by radiation induced crosslinking polymerization for biomedical applications.

AIMS: Keeping in view the therapeutic and pharmaceutical applications of sterculia gum polysaccharide in consideration, its modification has been carried out through grafting and crosslinking to develop the hydrogels for enhanced biomedical applications. Radiation method was used for formation of sterile network of sterculia gum, carbopol and graphene oxide (GO). These polymers were characterized by Cryo-SEMs, AFM, 13C NMR solid state, swelling studies. Some biomedical properties of hydrogels like thrombogenicity, haemolytic potential, antioxidant activity, mucoadhesion and gel strength were determined along with the drug delivery studies. SCOPE: In the present work, sterile polysaccharide gum based drug delivery system was developed for the slow delivery of gemcitabine, an anti-cancer drug, to overcome its side. CONCLUSIONS: The release profile of anti-cancer drug "gemcitabine" followed non-Fickian diffusion mechanism and release profile was best fitted in Korsmeyer-Peppas kinetic model of drug release. The hydrogels were found to be non-thrombogenic, non-haemolytic, mucoadhesive and antioxidant in nature. Incorporation of the GO nano-sheets in the composite hydrogel matrix has improved its mechanical and drug delivery properties and also exerted strong influence on the network density and mesh size of the hydrogels.

Combined Effects of Supersaturation Rates and Doses on the Kinetic-Solubility Profiles of Amorphous Solid Dispersions Based on Water-Insoluble Poly(2-hydroxyethyl methacrylate) Hydrogels.

Under nonsink dissolution conditions, the kinetic-solubility profiles of amorphous solid dispersions (ASDs) based on soluble carriers typically exhibit so-called "spring-and-parachute" concentration-time behaviors. However, the kinetic-solubility profiles of ASDs based on insoluble carriers (including hydrogels) are known to show sustained supersaturation during nonsink dissolution through a matrix-regulated diffusion mechanism by which the supersaturation of the drug is built up gradually and sustained over an extended period without any dissolved polymers acting as crystallization inhibitors. Despite previous findings demonstrating the interplay between supersaturation rates and total doses on the kinetic-solubility profiles of soluble amorphous systems (including ASDs based on dissolution-regulated releases from soluble polymer carriers), the combined effects of supersaturation rates and doses on the kinetic-solubility profiles of ASDs based on diffusion-regulated releases from water-insoluble carriers have not been investigated previously. Thus, the objective of this study is to examine the impacts of total doses and supersaturation-generation rates on the resulting kinetic-solubility profiles of ASDs based on insoluble hydrogel carriers. We employed a previously established ASD-carrier system based on water-insoluble-cross-linked-poly(2-hydroxyethyl methacrylate) (PHEMA)-hydrogel beads and two poorly water soluble model drugs: the weakly acidic indomethacin (IND) and the weakly basic posaconazole (PCZ). Our results show clearly for the first time that by using the smallest-particle-size fraction and a high dose (i.e., above the critical dose), it is indeed possible to significantly shorten the duration of sustained supersaturation in the kinetic-solubility profile of an ASD based on a water-insoluble hydrogel carrier, such that it resembles the spring-and-parachute dissolution profiles normally associated with ASDs based on soluble carriers. This generates sufficiently rapid initial supersaturation buildup above the critical supersaturation, resulting in more rapid precipitation. Above this smallest-particle-size range, the matrix-diffusion-regulated nonlinear rate of drug release gets slower, which results in a more modest rate of supersaturation buildup, leading to a maximum supersaturation below the critical-supersaturation level without appreciable precipitation. The area-under-the-curve (AUC) values of the in vitro kinetic-solubility concentration-time profiles were used to correlate the corresponding trends in dissolution enhancement. There are observed monotonic increases in AUC values with increasing particle sizes for high-dose ASDs based on water-insoluble hydrogel matrixes, as opposed to the previously reported AUC maxima at some intermediate supersaturation rates or doses in soluble amorphous systems, whereas in the case of low-dose ASDs (i.e., below the critical dose levels), crystallization would be negligible, leading to sustained supersaturation with all particle sizes (i.e., eventually reaching the same maximum supersaturation) and the smallest particle size reaching the maximum supersaturation the fastest. As a result, the smallest particle sizes yield the largest AUC values in the case of low-dose ASDs based on water-insoluble hydrogel matrixes. In addition to probing the interplay between the supersaturation-generation rates and total doses in ASDs based on insoluble hydrogel carriers, our results further support the fact that through either increasing the hydrogel-particle size or lowering the total dose to achieve maximum supersaturation still below the critical-supersaturation level, it is possible to avoid drug precipitation so as to maintain sustained supersaturation.