Chitosan citrate as multifunctional polymer for vaginal delivery. Evaluation of penetration enhancement and peptidase inhibition properties

Quality by Design-Guided Systematic Development and Optimization of Mucoadhesive Buccal Films

Mucoadhesive buccal films have found increased popularity in pharmaceutical drug delivery due to the several advantages that they possess. The present study strives to develop and optimize chitosan-based mucoadhesive buccal films by relying on quality-by-design (QbD) principles. Previous knowledge and experience were employed to firstly identify the critical quality attributes (CQAs), followed by a thorough risk assessment, which led to the selection of seven critical material attributes and process parameters, namely, the polymer grade and concentration, the plasticizer type and concentration, the citric acid (CA) concentration, the amount of the casted solution, and the drying condition. Their effects on the breaking hardness and mucoadhesivity, selected as CQAs, were investigated in three steps by three designs of the experiment (DoE). The medium molecular weight of chitosan (CH) was the preferred choice in the optimized formulation, and its concentration was the most important factor affecting the CQAs, thickness, and moisture content of the films. It was found that 0.364 g/cm2 was the suitable amount of the casting solution, and its optimum drying conditions were presented in the form of a design space. Glycerol (Gly) was the best choice as a plasticizer, and a design space representing several combinations of CH and CA concentrations that produce films with the required quality was constructed at a fixed concentration of 35% Gly. A formula from this design space was selected and employed to load with two model drugs to test its drug-carrying properties for drugs with different physicochemical characteristics. Uniform drug distribution with an immediate release profile was achieved in both drugs, although one of the CQAs was outside of the specifications in the case of lidocaine-containing film. To summarize, the obtention of the optimum mucoadhesive buccal film based on CH was efficiently facilitated by the rational application of QbD principles and the DoE approach.

Stability, Permeability and Cytotoxicity of Buccal Films in Allergy Treatment

Oral mucoadhesive systems, such as polymer films, are among innovative pharmaceutical products. These systems can be applied in swallowing problems and can also be used in geriatrics and paediatrics. In our earlier work, we successfully formulated buccal mucoadhesive polymer films, which contained cetirizine-hydrochloride (CTZ) as the API. The present study focused on investigating the stability and permeability of the prepared films. The stability of the films was studied with an accelerated stability test. During the stability test, thickness, breaking hardness and in vitro mucoadhesivity were analysed. Furthermore, the interactions were studied with FT-IR spectroscopy, and the changes in the amount of the API were also monitored. Cytotoxicity and cell line permeability studies were carried out on TR 146 buccal cells. Compositions that can preserve more than 85% of the API after 6 months were found. Most of the compositions had a high cell viability of more than 50%. Citric acid (CA) decreased the stability and reduced every physical parameter of the films. However, cell line studies showed that the permeability of the films was enhanced. In our work, we successfully formulated CTZ-containing buccal films with adequate stability, high cell viability and appropriate absorption properties.

Citric Acid: A Multifunctional Pharmaceutical Excipient

Citric acid, a tricarboxylic acid, has found wide application in the chemical and pharmaceutical industry due to its biocompatibility, versatility, and green, environmentally friendly chemistry. This review emphasizes the pharmaceutical uses of citric acid as a strategic ingredient in drug formulation while focusing on the impact of its physicochemical properties. The functionality of citric acid is due to its three carboxylic groups and one hydroxyl group. These allow it to be used in many ways, including its ability to be used as a crosslinker to form biodegradable polymers and as a co-former in co-amorphous and co-crystal applications. This paper also analyzes the effect of citric acid in physiological processes and how this effect can be used to enhance the attributes of pharmaceutical preparations, as well as providing a critical discussion on the issues that may arise out of the presence of citric acid in formulations.

Recent Advances in the Excipients Used in Modified Release Vaginal Formulations

The formulation of an ideal vaginal drug delivery system (DDS), with the requisite properties, with respect to safety, efficacy, patient compliance, aesthetics, harmonization with the regulatory requirements, and cost, requires a meticulous selection of the active ingredients and the excipients used. Novel excipients defined by diversity and multifunctionality are used in order to ameliorate drug delivery attributes. Synthetic and natural polymers are broadly used in pharmaceutical vaginal formulations (solid, semi-solid dosage forms, implantable devices, and nanomedicines) with a promising perspective in improving stability and compatibility issues when administered topically or systemically. Moreover, the use of biopolymers is aiming towards formulating novel bioactive, biocompatible, and biodegradable DDSs with a controllable drug release rate. Overviewing vaginal microenvironment, which is described by variable and perplexed features, a perceptive choice of excipients is essential. This review summarizes the recent advances on the excipients used in modified vaginal drug delivery formulations, in an attempt to aid the formulation scientist in selecting the optimal excipients for the preparation of vaginal products.

Chitosan-microencapsulated rhEGF in promoting wound healing

AIMS

Chitosan and epidermal growth factor (EGF) have been shown to improve wound healing. This study investigates the healing effects of a spray solution (NewEpi, JoyCom Bio-Chem Co. Ltd., Taiwan) containing recombinant human EGF (rhEGF) delivered via a newly patented technology-chitosan microencapsulated nanoparticles.

METHODS

On Wistar rats, two full-thickness wounds on the dorsum bilateral of the spine were created. The rats were randomised to the following treatment groups: hydrogel, wet dressing, foam, rhEGF spray and rhEGF spray+foam. Sterile dressings were applied and changed daily. A total of 2μg of rhEGF was administered in two sprays during each dressing change. All animals were euthanised on day 14. Tissue samples were taken from the wound bed, including an area of 2cm surrounding the wound margin for histological evaluations.

RESULTS

Wounds treated with the rhEGF spray achieved the greatest size reduction by day 14 compared with other types of conventional dressings. An overall significant difference in levels of collagen synthesis existed between groups (p<0.01). Pair-wise comparisons showed that the rhEGF spray treatment significantly promoted higher levels of mature Type I collagen than any other conventional dressings (p<0.01), whereas non-rhEGF treatments resulted in higher levels of Type III collagen. The regenerated tissue in rhEGF spray treatment groups was also in alignment with that of normal skin. Epidermis, dermis and hair follicles were easily observed in wounds treated with the rhEGF spray.

CONCLUSION

The major challenge of topical application of rhEGF was overcome by using a new drug delivery technology: chitosan-rhEGF nanoparticles. The positive healing effects observed in this study suggest the therapeutic potentials of this novel rhEGF topical spray solution.

Recent Advances in Polymer-Based Vaginal Drug Delivery Systems

The vagina has been considered a potential drug administration route for centuries. Most of the currently marketed and investigated vaginal formulations are composed with the use of natural or synthetic polymers having different functions in the product. The vaginal route is usually investigated as an administration site for topically acting active ingredients; however, the anatomical and physiological features of the vagina make it suitable also for drug systemic absorption. In this review, the most important natural and synthetic polymers used in vaginal products are summarized and described, with special attention paid to the properties important in terms of vaginal application. Moreover, the current knowledge on the commonly applied and innovative dosage forms designed for vaginal administration was presented. The aim of this work was to highlight the most recent research directions and indicate challenges related to vaginal drug administrations. As revealed in the literature overview, intravaginal products still gain enormous scientific attention, and novel polymers and formulations are still explored. However, there are research areas that require more extensive studies in order to provide the safety of novel vaginal products.

New Perspective Enteric-Coated Tablet Dosage Form for Oral Administration of Ceftriaxone: In Vitro and In Vivo Assessments

Ceftriaxone (CTX) is a widely used injectable third-generation cephalosporin that exhibits broad-spectrum antibacterial activity. Unfortunately, the oral route of this drug suffers different encumbrances, such as instability in the upper part of the GIT and enzymatic degradation, as well as poor permeability. There is no reported tablet dosage form for this drug. In this respect, the authors investigated the possibility of developing an enteric-coated oral tablet of CTX that would be helpful for better patient compliance. The tablet consists of directly compressed core of CTX, citric acid (CA), sodium chloride (NaCl), and two biopolymers-chitosan (CH), a permeation enhancer, and silicified microcrystalline cellulose (SMCC), a wicking agent. Both biopolymers are naturally occurring polysaccharides that are biodegradable in the colon and able to incorporate acid labile drugs. CA is a pH modulator to protect CTX from protease enzymes, while NaCl is a translocation enhancer that helps drug penetration. The enteric coat of the core was shellac (SH) with plasticizer glycerol tristearate (GTS) and CA that was applied by direct compression (dry coating). The solventless heat curable coat resulted in an enteric-coated tablet that complies with the USP pharmacopeia. The optimized formula was further subjected to in vitro release and stability studies, as well as ingredient compatibility. In vivo oral bioavailability of the enteric-coated tablets in rabbits gave promising results (absolute bioavailability of about 80%). Synergistically, all ingredients together augmented oral bioavailability of CTX. This developed formula could be a perspective delivery system for those drugs intended to be absorbed from the colon such as peptides and peptide-like drugs.

Design, Characterization, and Biopharmaceutical Behavior of Nanoparticles Loaded with an HIV-1 Fusion Inhibitor Peptide

New therapeutic alternatives to fight against the spread of HIV-1 are based on peptides designed to inhibit the early steps of HIV-1 fusion in target cells. However, drawbacks, such as bioavailability, short half-life, rapid clearance, and poor ability to cross the physiological barriers, make such peptides unattractive for the pharmaceutical industry. Here we developed, optimized, and characterized polymeric nanoparticles (NPs) coated with glycol chitosan to incorporate and release an HIV-1 fusion inhibitor peptide (E1) inside the vaginal mucosa. The NPs were prepared by a modified double emulsion method, and optimization was carried out by a factorial design. In vitro, ex vivo, and in vivo studies were carried out to evaluate the optimized formulation. The results indicate that the physicochemical features of these NPs enable them to incorporate and release HIV fusion inhibitor peptides to the vaginal mucosa before the fusion step takes place.

Mucoadhesive Properties of Eudragit®RS100, Eudragit®S100, and Poly(ε-caprolactone) Nanocapsules: Influence of the Vehicle and the Mucosal Surface

The use of polymers as mucoadhesive materials has been explored in several drug delivery systems. It is well known that the resulting mucoadhesiveness not only depends on the polymers by themselves, but also on the way they are delivered and on the application target. However, little attention has been given to the combined effect of such characteristics. Therefore, the objective of this study is to analyze the mucoadhesion resulting from combined effects of nanocapsules produced with polymers of different ionic properties, Eudragit®RS100, Eudragit®S100, or poly(ε-caprolactone), when they are incorporated into different vehicles (suspension, hydrogel, and powder) and applied on different mucosal surfaces (mucin, porcine vaginal, and buccal mucosa). Mucoadhesion was measured by a tensile stress tester. Our findings show that polymeric self-assembling as nanocapsules improved the mucoadhesion of the polymers. Eudragit®RS100 nanocapsules have the best performance, independently of the vehicle and surface used. Regarding the vehicle, hydrogels showed higher adhesion when compared to suspensions and powders. When considering different types of surfaces, mucin presented a similar pattern like the animal mucosa, but it overestimated the mucoadhesiveness of all formulations. In conclusion, this study demonstrated that the best strategy to achieve high mucoadhesive formulations is by incorporating Eudragit®RS100 nanocapsules in hydrogels. Moreover, mucin is a suitable substrate to compare and screen different formulations but not as a conclusive estimation of the mucoadhesion values that can be achieved. These results are summarized in a decision tree that can help to understand different strategies of combination of these factors and the expected outcomes.

A novel ionic amphiphilic chitosan derivative as a stabilizer of nanoemulsions: Improvement of antimicrobial activity of Cymbopogon citratus essential oil

Amphiphilic chitosans have been recently proposed to improve delivery of poorly soluble drugs. In the present paper a derivative obtained by ionic interaction between chitosan and oleic acid was for the first time studied to physically stabilize o/w nanoemulsions of an antimicrobial essential oil, Cymbopogon citratus (Lemongrass), in a low energy and mild conditions emulsification process. The novel combination of spontaneous emulsification process with chitosan oleate amphiphilic properties resulted in a stable dispersion of a few hundred nanometer droplets. Positive zeta potential confirmed the presence of a chitosan shell around the oil droplets, which is responsible for the nanoemulsion physical stabilization and for the maintenance of chitosan bioactive properties, such as mucoadhesion. Cytotoxicity test was performed on four different cell lines (HEp-2, Caco-2, WKD and McCoy cells) showing biocompatibility of the system. The maintenance and in some cases even a clear improvement in the essential oil antimicrobial activity towards nine bacterial and ten fungal strains, all of clinical relevance was verified for Lemongrass nanoemulsion.

A review of polymers as multifunctional excipients in drug dosage form technology

In the article, groups of multifunctional polymers used in drug dosage form technology were classified and evaluated. These compounds, in addition to their basic function as excipients, may have additional properties, e.g. stimuli sensitivity, enzyme inhibition, intestinal epithelium penetration enhancement, efflux pump inhibition, taste-masking, pharmacological activity and the ability to interact with enzymes responsible for drug metabolism. While classifying specific groups of multifunctional polymers, special emphasis was placed on the advantages of using them when designing new drug. Such advantages include, i.a., increasing substance bioavailability, improving substance stability during formulation and the possibility of obtaining forms of controlled or localized release to a specific site in the organism.

A novel gel based on an ionic complex from a dendronized polymer and ciprofloxacin: Evaluation of its use for controlled topical drug release

The development and characterization of a novel, gel-type material based on a dendronized polymer (DP) loaded with ciprofloxacin (CIP), and the evaluation of its possible use for controlled drug release, are presented in this work. DP showed biocompatible and non-toxic behaviors in cultured cells, both of which are considered optimal properties for the design of a final material for biomedical applications. These results were encouraging for the use of the polymer loaded with CIP (as a drug model), under gel form, in the development of a new controlled-release system to be evaluated for topical administration. First, DP-CIP ionic complexes were obtained by an acid-base reaction using the high density of carboxylic acid groups of the DP and the amine groups of the CIP. The complexes obtained in the solid state were broadly characterized using FTIR spectroscopy, XRP diffraction, DSC-TG analysis and optical microscopy techniques. Gels based on the DP-CIP complexes were easily prepared and presented excellent mechanical behaviors. In addition, optimal properties for application on mucosal membranes and skin were achieved due to their high biocompatibility and acute skin non-irritation. Slow and sustained release of CIP toward simulated physiological fluids was observed in the assays (in vitro), attributed to ion exchange phenomenon and to the drug reservoir effect. An in vitro bacterial growth inhibition assay showed significant CIP activity, corresponding to 38 and 58% of that exhibited by a CIP hydrochloride solution at similar CIP concentrations, against Staphylococcus aureus and Pseudomonas aeruginosa, respectively. However, CIP delivery was appropriate, both in terms of magnitude and velocity to allow for a bactericidal effect. In conclusion, the final product showed promising behavior, which could be exploited for the treatment of topical and mucosal opportunistic infections in human or veterinary applications.

Preparation and characterization of bioadhesive controlled-release gels of cidofovir for vaginal delivery

The aim of this study was to develop mucoadhesive and thermosensitive gels for vaginal delivery that would be able to provide a controlled release of the model drug, cidofovir. The study also monitored the drug's potential antiviral properties. Cidofovir was put into the form of a vaginal gel, using mucoadhesive and thermosensitive polymers such as chitosan, Carbopol 974P, HPMC, and poloxamer 407. The physicopharmaceutical properties and stability of the vaginal gel formulations were evaluated. The gel formulation which was prepared with HPMC K100M exhibited the highest viscosity, as well as maximum adhesiveness, cohesiveness, and mucoadhesion values. The results of antiviral activity studies, which used the bovine herpes virus type 1 virus infection in vitro model using Vero cells, demonstrated the antiherpetic effect of the cidofovir gel containing HPMC K100M, at least under in vitro conditions. The study found that a mucoadhesive vaginal gel containing cidofovir can be a promising and innovative alternative therapeutic system for the treatment of genital herpes simplex virus and human papilloma virus induced infections in women.

Mucoadhesive and thermogelling systems for vaginal drug delivery

This review focuses on two formulation approaches, mucoadhesion and thermogelling, intended for prolonging residence time on vaginal mucosa of medical devices or drug delivery systems, thus improving their efficacy. The review, after a brief description of the vaginal environment and, in particular, of the vaginal secretions that strongly affect in vivo performance of vaginal formulations, deals with the above delivery systems. As for mucoadhesive systems, conventional formulations (gels, tablets, suppositories and emulsions) and novel drug delivery systems (micro-, nano-particles) intended for vaginal administration to achieve either local or systemic effect are reviewed. As for thermogelling systems, poly(ethylene oxide-propylene oxide-ethylene oxide) copolymer-based and chitosan-based formulations are discussed as thermogelling systems. The methods employed for functional characterization of both mucoadhesive and thermogelling drug delivery systems are also briefly described.

Polymer-based nanocarriers for vaginal drug delivery

The vaginal delivery of various drugs is well described and its relevance established in current medical practice. Alongside recent advances and achievements in the fields of pharmaceutical nanotechnology and nanomedicine, there is an increasing interest in the potential use of different nanocarriers for the delivery of old and new pharmacologically active molecules with either therapeutic or prophylactic purposes. Nanosystems of polymeric nature in particular have been investigated over the last years and their interactions with mucosal fluids and tissues, as well as genital tract biodistribution upon vaginal administration, are now better understood. While different applications have been envisioned, most of the current research is focusing in the development of nano-formulations with the potential to inhibit the vaginal transmission of HIV upon sexual intercourse. The present work focuses its discussion on the potential and perils of polymer-based nanocarriers for the vaginal administration of different pharmacologically active molecules.

Development of chitosan oleate ionic micelles loaded with silver sulfadiazine to be associated with platelet lysate for application in wound healing

In the treatment of chronic wounds, topical application of anti-infective drugs such as silver sulfadiazine (AgSD) is of primary importance to avoid infections and accelerate wound repair. AgSD is used in burns and chronic wounds for its wide antibacterial spectrum, but presents limitations due to poor solubility and cytotoxicity. In the present work polymeric micelles obtained by self-assembling of chitosan ionically modified by interaction with oleic acid were developed as carriers for AgSD to overcome the drawbacks of the drug. The AgSD loaded micelles were intended to be associated in wound healing with platelet lysate (PL), a hemoderivative rich in growth factors. Unloaded micelles demonstrated good compatibility with both fibroblasts and PL. The relevance of chitosan concentration and of the ratio between chitosan and oleic acid to the drug loading and the particle size of nanoparticles was studied. A marked increase (up to 100 times with respect to saturated solution) of AgSD concentration in micelle dispersion was obtained. Moreover, the encapsulation reduced the cytotoxic effect of the drug towards fibroblasts and the drug incompatibility with PDGF-AB (platelet derived growth factor), chosen as representative of platelet growth factors.

Chitosan gel containing polymeric nanocapsules: a new formulation for vaginal drug delivery

The vaginal route of administration is an alternative for several treatments for either local or systemic pharmacological effects. However, the permanence of a drug in this route represents a challenge for formulation development that can be overcome by using nanoencapsulation and chitosan gel. Thus, this work aimed to evaluate the performance of chitosan hydrogels containing cationic and anionic acrylic-based nanocapsules (Eudragit^® RS 100 and Eudragit^® S 100, respectively) with Nile red as a model of lipophilic substance in the vaginal route of administration, as measured by increases in the residence time and the penetration of these formulations. Several formulations were prepared with increasing chitosan concentrations, and were analyzed in terms of pH and rheological behavior so that the most suitable formulation could be selected. The enhancement of the adhesion (tensile stress test and washability profile) and penetration (confocal laser scanning microscopy and extraction followed by quantification) properties of the formulations, when applied to porcine vaginal mucosa, were evaluated. The nanocapsule suspensions produced presented adequate properties: size of approximately 200 nm (polydispersity index of ≤v0.2); zeta potential around +10 mV for the cationic formulation and -10 mV for the anionic formulation; and pH values of 6.1±0.1 (Eudragit RS 100), 5.3±0.2 (Eudragit S 100), 6.2±0.1 (Nile red loaded Eudragit RS 100), and 5.1±0.1 (Nile red loaded Eudragit S 100). The chitosan formulation presented suitable viscosity for vaginal application and acidic pH (approximately 4.5). The tensile stress test showed that both formulations containing polymeric nanocapsules presented higher mucoadhesion when compared with the formulation without nanocapsules. In the washability experiment, no significant differences were found between formulations. Confocal microscopy and fluorescence quantification after extraction from the mucosa showed higher penetration of Nile red when it was nanoencapsulated, particularly in cationic nanocapsules. The formulations developed based on chitosan gel vehicle at 2.5% weight/weight containing polymeric nanocapsules, especially the cationic nanocapsules, demonstrated applicability for the vaginal delivery of hydrophobic substances.

Chitosan-coated liposomes for topical vaginal therapy: assuring localized drug effect

The choice of drug therapy in pregnant patients suffering from vaginal infections is limited by the safety profile of the drug. Assuring the efficient topical therapy to avoid systemic absorption is considered the best therapy option. Chitosan-coated liposomes have been developed and optimized to assure localized therapy of clotrimazole. Chitosan was selected as mucoadhesive polymer both to prolong system's retention at the vaginal site and act on biofilms responsible for high recurrence of infections. Sonicated liposomes were coated with chitosan in three different concentrations, namely 0.1, 0.3 and 0.6% (w/v). Clotrimazole-containing (22 μg/mg lipid) chitosan-coated liposomes were in the size range of 100-200 nm. The in vitro release studies confirmed prolonged release of clotrimazole from both non-coated and chitosan-coated liposomes as compared to control. The ex vivo penetration experiments performed on the pregnant sheep vaginal tissue showed that coated liposomes assured increased clotrimazole tissue retention and reduced its penetration as compared to the control. Mucin studies revealed that the coating with lower chitosan concentration increased the system's mucoadhesive potential, as compared to coating with higher concentrations. These results provide a good platform for further in vivo animal studies on mucoadhesive liposomes destined to localized vaginal therapy.

Marine medicinal glycomics

Glycomics is an international initiative aimed to understand the structure and function of the glycans from a given type of cell, tissue, organism, kingdom or even environment, as found under certain conditions. Glycomics is one of the latest areas of intense biological research. Glycans of marine sources are unique in terms of structure and function. They differ considerably from those of terrestrial origin. This review discusses the most known marine glycans of potential therapeutic properties. They are chitin, chitosan, and sulfated polysaccharides named glycosaminoglycans, sulfated fucans, and sulfated galactans. Their medical actions are very broad. When certain structural requirements are found, these glycans can exhibit beneficial effects in inflammation, coagulation, thrombosis, cancer growth/metastasis, and vascular biology. Both structure and therapeutic mechanisms of action of these marine glycans are discussed here in straight context with the current glycomic age through a project suggestively named marine medicinal glycomics.

Hydrogels in mucosal delivery

The concept of mucoadhesion and the molecular design requirements for the synthesis of mucoadhesive agents are both well understood and, as a result, hydrogel formulations that may be applied to mucosal surfaces are readily accessible. Nanosized hydrogel systems that make use of biological recognition or targeting motifs, by reacting to disease-specific environmental triggers and/or chemical signals to affect drug release, are now emerging as components of a new generation of therapeutics that promise improved residence time, faster response to stimuli and triggered release.

Methotrexate-loaded chitosan- and glycol chitosan-based nanoparticles: a promising strategy for the administration of the anticancer drug to brain tumors

Brain tumor treatment employing methotrexate (MTX) is limited by the efflux mechanism of Pg-p on the blood-brain barrier. We aimed to investigate MTX-loaded chitosan or glycol chitosan (GCS) nanoparticles (NPs) in the presence and in the absence of a coating layer of Tween 80 for brain delivery of MTX. The effect of a low Tween 80 concentration was evaluated. MTX NPs were formulated following the ionic gelation technique and size and zeta potential measurements were acquired. Transport across MDCKII-MDR1 monolayer and cytotoxicity studies against C6 glioma cell line were also performed. Cell/particles interaction was visualized by confocal microscopy. The particles were shown to be cytotoxic against C6 cells line and able to overcome MDCKII-MDR1 cell barrier. GCS-based NPs were the most cytotoxic NPs. Confocal observations highlighted the internalization of Tween 80-coated fluorescent NPs more than Tween 80-uncoated NPs. The results suggest that even a low concentration of Tween 80 is sufficient for enhancing the transport of MTX from the NPs across MDCKII-MDR1 cells. The nanocarriers represent a promising strategy for the administration of MTX to brain tumors which merits further investigations under in vivo conditions.

Platelet lysate mucohadesive formulation to treat oral mucositis in graft versus host disease patients: a new therapeutic approach

Optimal treatment of oral mucositis (OM) due to graft versus host disease (GvHD) is currently not available. Platelet-derived growth factors (PDGFs) have high capability for tissue healing and may play a role in repairing the mucosal barrier. The aim of the present work was to develop a mucoadhesive formulation to administer platelet lysate to oral cavity prolonging contact time of platelet lysate with oral mucosa. The mucoadhesive formulation was characterized for in vitro properties (PDGF-AB concentration, mucoadhesive properties, cytotoxicity, fibroblast proliferation, wound healing). Moreover, a preliminary clinical study on seven GvHD patients with OM refractory to other therapies was conducted, to evaluate feasibility, safety, and efficacy. GVPL (mucoadhesive gel vehicle mixed with platelet lysate)showed good mucoadhesive properties; additionally, it was characterized by good biocompatibility in vitro on fibroblasts and it was able to enhance fibroblast proliferation and wound healing, maintaining the efficacy for up to 14 days following storage at 2-8°C. In vivo, clinical response was good-to-complete in five, fair in one, none in the remaining one. The in vitro results indicate that GVPL has optimal mucoadhesive and healing enhancer properties, maintained over time (up to 14 days); preliminary clinical results suggest that oral application of platelet lysate-loaded mucoadhesive formulation is feasible, safe, well tolerated, and effective. A larger controlled randomized study is needed.

Structural and Functional Analysis of the Complex between Citrate and the Zinc Peptidase Carboxypeptidase A

A high-resolution carboxypeptidase-Zn(2+)-citrate complex was studied by X-ray diffraction and enzyme kinetics for the first time. The citrate molecule acts as a competitive inhibitor of this benchmark zinc-dependent peptidase, chelating the catalytic zinc ion in the active site of the enzyme and inducing a conformational change such that carboxypeptidase adopts the conformation expected to occur by substrate binding. Citrate adopts an extended conformation with half of the molecule facing the zinc ion, while the other half is docked in the S1' hydrophobic specificity pocket of the enzyme, in contrast with the binding mode expected for a substrate like phenylalanine or a peptidomimetic inhibitor like benzylsuccinic acid. Combined structural and enzymatic analysis describes the characteristics of the binding of this ligand that, acting against physiologically relevant zinc-dependent proteases, may serve as a general model in the design of new drug-protecting molecules for the oral delivery of drugs of peptide origin.

In vitro Evaluation of Acyclovir/Chitosan Floating Systems

Chitosan (CS) floating lyophilized formulations (L) for gastric drug delivery of acyclovir (ACV) have been developed. The freeze-dried formulations were obtained from acidic aqueous suspensions prepared with different ACV/CS ratios. No changes in ACV crystallinity were observed during X-ray diffraction powder studies as a consequence of the manufacturing process. Considering that fed and fasted states modified the intragastric pH, swelling and in vitro dissolution studies were carried out in different acidic media (0.1 M HCl and progressive pH medium) in order to understand the influence of these physiological states on ACV/CS formulations. Swelling behavior of the floating lyophilized formulations was dependent on CS and ACV proportions within L and on medium nature due to pH dependent CS solubility. Furthermore, no interactions between ACV and CS were detected in solid state according to the X-ray studies. In vitro dissolution of ACV from L was influenced by the swelling behavior. However, it is feasible to optimize the ACV/CS ratios to achieve a desired formulation that releases the total quantity of ACV at a specific time. Moreover, floatability was assessed by buoyancy tests. The results demonstrated that the freeze-drying process achieved effective floating systems capable of remaining within the stomach while the total amount of ACV is released from L.

Investigation of the physicochemical and physicomechanical properties of a novel intravaginal bioadhesive polymeric device in the pig model

The purpose of this study was to develop and evaluate the bioadhesivity, in vitro drug release, and permeation of an intravaginal bioadhesive polymeric device (IBPD) loaded with 3'-azido-3'-deoxythymidine (AZT) and polystyrene sulfonate (PSS). Modified polyamide 6,10, poly(lactic-coglycolic acid), polyacrylic acid, polyvinyl alcohol, and ethylcellulose were blended with model drugs AZT and PSS as well as radio-opaque barium sulfate (BaSO4) and then compressed into caplet devices on a tableting press. One set of devices was coated with 2% w/v pentaerythritol polyacrylic acid (APE-PAA) while another remained uncoated. Thermal analysis was performed on the constituent polymers as well the IBPD. The changes in micro-environmental pH within the simulated human vaginal fluid due to the presence of the IBPD were assessed over a period of 30 days. Textural profile analysis indicated that the bioadhesivity of the APE-PAA-coated devices (3.699 +/- 0.464 N; 0.0098 +/- 0.0004 J) was higher than that of the uncoated devices (1.198 +/- 0.150 N; 0.0019 +/- 0.0001 J). In addition, BaSO4-facilitated X-ray imaging revealed that the IBPD adhered to pig vaginal tissue over the experimental period of 30 days. Controlled drug release kinetics was obtained over 72 days. During a 24-h permeation study, an increase in drug flux for both AZT (0.84 mg cm(-2) h(-1)) and PSS (0.72 mg cm(-2) h(-1)) was realized up to 12 h and thereafter a steady-state was achieved. The diffusion and dissolution dynamics were mechanistically deduced based on a chemometric and molecular structure modeling approach. Overall, results suggested that the IBPD may be sufficiently bioadhesive with desirable physicochemical and physicomechanical stability for use as a prolonged intravaginal drug delivery device.

Antifungal activity of low molecular weight chitosan against clinical isolates of Candida spp

Chitosan is a natural polymer derived from chitin, a structural component of fungi, insects and shrimp, which exerts antimicrobial effects against bacteria and fungi. The aim of this study was to investigate the in vitro antifungal activity of low molecular weight chitosan (LMWC), and the potential synergy between chitosan and a currently used antifungal drug, fluconazole. The in vitro minimal inhibitory concentrations (MICs) of chitosan and fluconazole against 105 clinical Candida isolates were measured by the broth microdilution method. LMWC exhibited a significant antifungal activity, inhibiting over 89.9% of the clinical isolates examined (68.6% of which was completely inhibited). The species included several fluconazole-resistant strains and less susceptible species such as C. glabrata, which was inhibited at a concentration of 4.8 mg/l LMWC. Although some strains were susceptible at pH 7.0, a greater antifungal activity of LMWC was observed at pH 4.0. There was no evidence of a synergistic effect of the combination of LMWC and fluconazole at pH 7.0. This is the first report in which the antifungal activity of LMWC was investigated with clinical Candida strains. The use of LMWC as an antifungal compound opens new therapeutic perspectives, as the low toxicity of LMWC in humans supports its use in new applications in an environment of pH 4.0-4.5, such as a topical agent for vulvovaginal candidiasis.

Chitins and chitosans as immunoadjuvants and non-allergenic drug carriers

Due to the fact that some individuals are allergic to crustaceans, the presumed relationship between allergy and the presence of chitin in crustaceans has been investigated. In vivo, chitin is part of complex structures with other organic and inorganic compounds: in arthropods chitin is covalently linked to proteins and tanned by quinones, in fungi it is covalently linked to glucans, while in bacteria chitin is diversely combined according to Gram(+/-) classification. On the other hand, isolated, purified chitin is a plain polysaccharide that, at the nano level, presents itself as a highly associated structure, recently refined in terms of regularity, nature of bonds, crystallinity degree and unusual colloidal behavior. Chitins and modified chitins exert a number of beneficial actions, i.e., (i) they stimulate macrophages by interacting with receptors on the macrophage surface that mediate the internalization of chitin particles to be degraded by lysozyme and N-acetyl-beta-glucosaminidase (such as Nod-like, Toll-like, lectin, Dectin-1, leukotriene 134 and mannose receptors); (ii) the macrophages produce cytokines and other compounds that confer non-specific host resistance against bacterial and viral infections, and anti-tumor activity; (iii) chitin is a strong Th1 adjuvant that up-regulates Th1 immunity induced by heat-killed Mycobacterium bovis, while down- regulating Th2 immunity induced by mycobacterial protein; (iv) direct intranasal application of chitin microparticles into the lung was also able to significantly down-regulate allergic response to Dermatophagoids pteronyssinus and Aspergillus fumigatus in a murine model of allergy; (v) chitin microparticles had a beneficial effect in preventing and treating histopathologic changes in the airways of asthmatic mice; (vi) authors support the fact that chitin depresses the development of adaptive type 2 allergic responses. Since the expression of chitinases, chitrotriosidase and chitinase-like proteins is greatly amplified during many infections and diseases, the common feature of chitinase-like proteins and chitinase activity in all organisms appears to be the biochemical defense of the host. Unfortunately, conceptual and methodological errors are present in certain recent articles dealing with chitin and allergy, i.e., (1) omitted consideration of mammalian chitinase and/or chitotriosidase secretion, accompanied by inactive chitinase-like proteins, as an ancestral defensive means against invasion, capable to prevent the insurgence of allergy; (2) omitted consideration of the fact that the mammalian organism recognizes more promptly the secreted water soluble chitinase produced by a pathogen, rather than the insoluble and well protected chitin within the pathogen itself; (3) superficial and incomplete reports and investigations on chitin as an allergen, without mentioning the potent allergen from crustacean flesh, tropomyosine; (4) limited perception of the importance of the chemical/biochemical characteristics of the isolated chitin or chitosan for the replication of experiments and optimization of results; and (5) lack of interdisciplinarity. There is quite a large body of knowledge today on the use of chitosans as biomaterials, and more specifically as drug carriers for a variety of applications: the delivery routes being the same as those adopted for the immunological studies. Said articles, that devote attention to the safety and biocompatibility aspects, never reported intolerance or allergy in individuals and animals, even when the quantities of chitosan used in single experiments were quite large. Therefore, it is concluded that crab, shrimp, prawn and lobster chitins, as well as chitosans of all grades, once purified, should not be considered as "crustacean derivatives", because the isolation procedures have removed proteins, fats and other contaminants to such an extent as to allow them to be classified as chemicals regardless of their origin.

FG90 chitosan as a new polymer for metronidazole mucoadhesive tablets for vaginal administration

Topical administration of the antibacterial metronidazole (MET) represents the most common therapy in the treatment of bacterial vaginosis (BV). The formulations generally available for BV therapy are creams, gels, vaginal lavages and vaginal suppositories. In this study, a new dosage form, containing MET, was developed with the aim to realize vaginal mucoadhesive tablets by including bioadhesive polymers as chitosan (FG90C), polyvinylpyrrolidone (PVPK90) and polycarbophil (PCPAA1), blended in different ratios. All formulations were characterized by studies of DSC, friability, hardness, hydration, mucoadhesion, in vitro release and antibacterial activity. All polymer mixtures employed were used to prepare tablets with the compactness and hardness so as allow the application on vaginal mucosa. FG90C performances improved in particular when mixed to PVPK90 (1:1 ratio). This kind of delivery system is suitable for formulating MET for topical application representing a good alternative to traditional dosage forms for vaginal topical administration.