Hydrogel delivery systems for vaginal and oral applications

In Vitro and Ex Vivo Evaluation of Novel Methacrylated Chitosan-PNIPAAm-Hyaluronic Acid Hydrogels Loaded with Progesterone for Applications in Vaginal Delivery

Miscarriage is defined as the loss of a pregnancy before 24 weeks and administration of progesterone in pregnancy has considerably decreased the risk of premature birth. Progesterone (PGT) starting from the luteal phase stabilizes pregnancy, promotes differentiation of the endometrium, and facilitates the implantation of the embryo. Within the present study, novel hybrid hydrogels based on chitosan methacrylate (CHT), hyaluronic acid (HA), and poly(N-isopropylacrylamide) (PNIPAAm) for vaginal delivery of progesterone were evaluated. The hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) for structural identity assessment and evaluation of their morphological aspects. The ability to swell, the release capacity, enzymatic degradation, cytotoxicity, and mucoadhesion were also reported. The characterized hydrogels demonstrated mucoadhesive properties in contact with the vaginal tissue of swine and bovine origin as substrates, and biodegradability and controlled release in a simulated vaginal environment. Cytocompatibility tests confirmed the ability of the hydrogels and progesterone to support cell viability and growth. The results showed pH-dependent behavior, controlled drug release, good cytocompatibility, and mucoadhesive properties. The hydrogels with higher chitosan amounts demonstrated better bioadhesive properties. This study provides insights into the potential of these hydrogels for the controlled vaginal delivery of progesterone, with promising therapeutic effects and no cytotoxicity observed. The experimental results indicated that a composition with a moderate content of PNIPAAm was suitable for the controlled delivery of progesterone.

Vaginal Drug Delivery Systems to Control Microbe-Associated Infections

The vagina has been regarded as a crucial route for drug delivery. Despite the wide range of available vaginal dosage forms for vaginal infection control, poor drug absorptivity remains a significant challenge due to various biological barriers in the vagina, such as mucus, epithelium, immune systems, and others. To overcome these barriers, different types of vaginal drug delivery systems (VDDSs), with outstanding mucoadhesive, mucus-penetrating properties, have been designed to enhance the absorptivity of vagina-administered agents in the past decades. In this Review, we introduce a general understanding of vaginal administration, its biological barriers, the commonly used VDDSs, such as nanoparticles and hydrogels, and their applications in controlling microbe-associated vaginal infections. Additionally, further challenges and concerns regarding the design of VDDSs will be discussed.

Cold Atmospheric Plasma-Activated Composite Hydrogel for an Enhanced and On-Demand Delivery of Antimicrobials

We present the concept of a versatile drug-loaded composite hydrogel that can be activated using an argon-based cold atmospheric plasma (CAP) jet to deliver both a drug and CAP-generated molecules, concomitantly, in a tissue target. To demonstrate this concept, we utilized the antibiotic gentamicin that is encapsulated in sodium polyacrylate (PAA) particles, which are dispersed within a poly(vinyl alcohol) (PVA) hydrogel matrix. The final product is a gentamicin-PAA-PVA composite hydrogel suitable for an on-demand triggered release using CAP. We show that by activating using CAP, we can effectively release gentamicin from the hydrogel and also eradicate the bacteria effectively, both in the planktonic state and within a biofilm. Besides gentamicin, we also successfully demonstrate the applicability of the CAP-activated composite hydrogel loaded with other antimicrobial agents such as cetrimide and silver. This concept of a composite hydrogel is potentially adaptable to a range of therapeutics (such as antimicrobials, anticancer agents, and nanoparticles) and activatable using any dielectric barrier discharge CAP device.

Antimicrobial Polymer-Based Hydrogels for the Intravaginal Therapies-Engineering Considerations

The review is focused on the hydrogel systems dedicated to the intravaginal delivery of antibacterial, antifungal and anti-Trichomonas vaginalis activity drugs for the treatment of gynaecological infections. The strategies for the enhancement of the hydrophobic drug solubility in the hydrogel matrix based on the formation of bigel systems and the introduction of nano- and microparticles as a drug reservoir are presented. Hydrogel carriers of natural and synthetic pharmacological substances, drug-free systems displaying antimicrobial activity thanks to the hydrogel building elements and systems combining the antimicrobial activity of both drug and polymer building components are distinguished. The design of hydrogels facilitating their administration and proper distribution in the vaginal mucosa and the vagina based on thermoresponsive systems capable of gelling at vaginal conditions and already-cross-linked injectable systems after reaching the yield stress are discussed. In addition, the mechanisms of hydrogel bioadhesion that regulate the retention time in the vagina are indicated. Finally, the prospects for the further development of hydrogel-based drug carriers in gynaecological therapies are highlighted.

Star-Shaped Poly(furfuryl glycidyl ether)-Block-Poly(glyceryl glycerol ether) as an Efficient Agent for the Enhancement of Nifuratel Solubility and for the Formation of Injectable and Self-Healable Hydrogel Platforms for the Gynaecological Therapies

In this paper, we present novel well-defined unimolecular micelles constructed a on poly(furfuryl glycidyl ether) core and highly hydrophilic poly(glyceryl glycerol ether) shell, PFGE-b-PGGE. The copolymer was synthesized via anionic ring-opening polymerization of furfuryl glycidyl ether and (1,2-isopropylidene glyceryl) glycidyl ether, respectively. MTT assay revealed that the copolymer is non-cytotoxic against human cervical cancer endothelial (HeLa) cells. The copolymer thanks to furan moieties in its core is capable of encapsulation of nifuratel, a hydrophobic nitrofuran derivative, which is a drug applied in the gynaecology therapies that shows a broad antimicroorganism spectrum. The study shows high loading capacity of the copolymer, i.e., 146 mg of nifuratel per 1 g of copolymer. The load unimolecular micelles were characterized using DLS and TEM microscopy and compared with the reference glyceryl glycerol ether homopolymer sample. The presence of numerous 1,2-diol moieties in the shell of PFGE-b-PGG macromolecules enabled the formation of reversible cross-links with 2-acrylamidephenylboronic acid-based polyacrylamide. The obtained hydrogels were both injectable and self-healable, which was confirmed with a rheological study.

Drug delivery systems based on biocompatible imino-chitosan hydrogels for local anticancer therapy

A series of drug delivery systems were prepared by chitosan hydrogelation with citral in the presence of an antineoplastic drug: 5-fluorouracil. The dynamic covalent chemistry of the imine linkage allowed the obtaining of supramolecular tridimensional architectures in which the drug has been homogenously dispersed. Fourier-transform infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WXRD) and polarized light microscopy (POM) measurements were used in order to follow the hydrogelation and drug encapsulation processes. The ability of the prepared systems to release the drug has been investigated by UV-Vis spectroscopy using a calibration curve and by fitting the results with different mathematic models. To mimic the behavior of the hydrogel matrix in bio-environmental conditions in view of applications, their enzymatic degradability was monitored in the presence of lysozyme. The in vivo side effects of the systems, in terms of their influence on the blood elements, biochemical and immune parameters were monitored on white Swiss mice by intraperitoneal administration of the injectable obtained hydrogels. All the characteristics of the obtained systems, such as micro-porous morphology, uniform drug encapsulation, enzymatic degradability, lack of side effects, other than the one of the drug itself, along with their ability to release the drug in a sustained manner proved that these material meet the requirements for the development of drug delivery systems, making them suitable for being applied in intraperitoneal chemotherapy.

Role of chitosan on controlling the characteristics and antifungal activity of bioadhesive fluconazole vaginal tablets

Vaginal fluconazole (FLZ) prolonged release tablets containing chitosan in physical blends with other bioadhesive polymers were designed. Chitosan was mixed with hydroxypropyl methylcellulose (HPMC), guar gum or sodium carboxymethyl cellulose (NaCMC) at different ratios and directly compressed into tablets. In-vitro release profiles of FLZ were monitored at pH 4.8. Compressing chitosan with HPMC at different ratios slowed FLZ release, however, time for 80% drug release (T80) did not exceed 4.3 h for the slowest formulation (F11). Adding of chitosan to guar gum at 1:2 ratio (F3) showed delayed release with T80 17.4 h while, in presence of PVP at 1:2:1 ratio (F5), T80 was 8.8 h. A blend of chitosan and NaCMC at 1:2 ratio (F15) showed prolonged drug release with T80 11.16 h. Formulations F5 and F15 showed fair physical characteristics for the powder and tablets and were subjected to further studies. Fast swelling was observed for F15 that reached 1160.53 ± 13.02% in 4 h with 2 h bioadhesion time to mouse peritoneum membrane compared with 458.83 ± 7.09% swelling with bioadhesion time exceeding 24 h for F5. Extensive swelling of F15 could indicate possible dehydration effect on vaginal mucosa. Meanwhile, antifungal activity against C. albicans was significantly high for F5.

Thermosensitive hydrogels a versatile concept adapted to vaginal drug delivery

Vaginal drug delivery represents an attractive strategy for local and systemic delivery of drugs otherwise poorly absorbed after oral administration. The rather dense vascular network, mucus permeability and the physiological phenomenon of the uterine first-pass effect can all be exploited for therapeutic benefit. However, several physiological factors such as an acidic pH, constant secretion, and turnover of mucus as well as varying thickness of the vaginal epithelium can impact sustained drug delivery. In recent years, polymers have been designed to tackle challenges mentioned above. In particular, thermosensitive hydrogels hold great promise due to their stability, biocompatibility, adhesion properties and adjustable drug release kinetics. Here, we discuss the physiological and anatomical uniqueness of the vaginal environment and how it impacts the safe and efficient vaginal delivery and also reviewed several thermosensitive hydrogels deemed suitable for vaginal drug delivery by addressing specific characteristics, which are essential to engage the vaginal environment successfully.

A 32full factorial design for development and characterization of a nanosponge-based intravaginal in situ gelling system for vulvovaginal candidiasis

The rationale behind present research effort was to enhance CTZ solubility and efficacyviaforming complex with hydroxypropyl β-cyclodextrin (HP-β-CD) nanosponges.

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.

Development, optimization and biological evaluation of chitosan scaffold formulations of new xanthine derivatives for treatment of type-2 diabetes mellitus

New xanthine derivatives as antidiabetic agents were synthesized and new chitosan formulations have been developed in order to improve their biological and pharmacokinetic profile. Their physicochemical properties in terms of particle size, morphology, swelling degree, crystalline state, the loading efficiency as well as in vitro release and biodegradation rate were evaluated. According to the results the optimized formulations have a high drug loading efficiency (more than 70%), small particle size, a good release profile in the simulated biological fluids (the percentage of cumulative release being more than 55%) and improved biodegradation rate in reference with chitosan microparticles. The presence of xanthine derivatives (6, 7) in chitosan microparticles was demonstrated by means of FTIR analysis. The X-ray diffraction (XRD) proved that xanthine derivatives present a crystalline state. The biological evaluation assays confirmed the antioxidant and antidiabetic effects of the xanthine derivatives (6, 7) and their chitosan formulations (CS-6, CS-7). Xanthine derivative 6 showed a high antiradical scavenging effect (DPPH remaining=41.78%). It also reduced the glucose blood level with 59.30% and recorded level of glycosylated hemoglobin was 4.53%. The effect of its chitosan formulation (CS-6) on the level of blood glucose (114.5mg/dl) was even more intense than the one recorded by pioglitazone (148.5mg/dl) when used as standard antidiabetic drug. These results demonstrated the potential application of xanthine derivative 6 and its chitosan formulation (CS-6) in the treatment of the diabetes mellitus syndrome.

Correlation study of structural parameters of bioadhesive polymers in designing a tunable drug delivery system

Keeping in view the importance of network structure in designing tunable drug delivery devices, in the present work, correlation between structural parameters and drug release profile has been determined for polysaccharide gum based polymers. These polymers have been characterized by SEMs, FTIR, (13)C NMR, XRD, TGA/DTA/DTG, DSC, and swelling studies. The mechanical, biocompatible, and mucoadhesive properties of polymers have also been determined. The polymer network parameters such as polymer volume fraction in the swollen state, Flory-Huggins interaction parameter, molecular weight of the polymer chain between two cross-links, cross-link density, and mesh size have been evaluated. Different kinetic models have been applied for the drug release profile of the antifungal drug fluconazole. The swelling and drug release occurred through a non-Fickian diffusion mechanism and a release profile best fitted in the Higuchi square root model. The polymers have been observed as non-thrombogenic, hemo-compatible, and mucoadhesive in nature and may be used in slow drug delivery applications to oral mucosa.

Thermosensitive hydrogel of hydrophobically-modified methylcellulose for intravaginal drug delivery

Hydrogels with the advantages of prolonging drug release and administration convenience are necessary for intravaginal drug delivery to prevent sexual transmission of human immunodeficiency virus and other vaginal infections. In this study, the thermosensitive hydrogel of methylcellulose modified by stearic acid (MCS) were evaluated in the presence of NaCl and phosphates, which exhibited sol-to-gel transition performance at body temperature or even lower. The in vitro cytotoxicity and in vivo mucosal irritation were investigated and the results showed that MCS hydrogel possessed good biocompatibility similar with hydroxyethyl cellulose (HEC) gel. Significantly, the release studies revealed that MCS hydrogel could control tenofovir sustained release for 10 h without burst release, longer than that from HEC gel or poloxamer 407 hydrogel. Therefore, MCS thermosensitive hydrogel would be a promising carrier for intravaginal delivery of antiviral drugs for long time controlled release.

Cress seed mucilage based buccal mucoadhesive gel of venlafaxine: in vivo, in vitro evaluation

Venlafaxine is a newer antipsychotic drug which shows first pass effect. Cress seed is also called as garden cress or green salad. This study examined the mechanical (gel strength, adhesiveness) and rheological properties of cress seed mucilage based gels that contain different ratios of carbopol 934 P (0.5-1.5%). In addition, diffusion of venlafaxine from gel formulations was evaluated. The selected formulation was further analyzed for pharmacokinetic parameters in rabbits. All formulations exhibited pseudoplastic flow with thixotropy. Formulation F5 showed the C(max) of 24.19 ± 0.72 ng/ml by buccal route of administration and 17.98 ± 1.15 ng/ml by oral route of administration. The bioavailability of F5 by buccal route was 54.44% and that of by oral route was 39.60%. A combination of the cress seed mucilage and carbopol 934 P resulted in a prolonged and higher venlafaxine delivery by buccal route of administration.

Formulation studies of benzydamine mucoadhesive formulations for vaginal administration

BACKGROUND

Vaginal cavity represents a good site for drug administration and delivery.

AIM

The aim of this work was the design of new mucoadhesive semisolid dosage forms for vaginal delivery of benzydamine.

METHOD

Simple gels, obtained by using sodium carboxymethylcellulose (NaCMC) and hydroxyethylcellulose (HEC), were employed as water phase of an oil-in-water emulsion (O/W cream) to obtain emulgels, more stable and manageable than gels. Successively, in order to modify the emulgel consistency, the ingredient cetostearylic alcohol was replaced by the same amount of gel or vaseline. All the preparations were submitted to mucoadhesion and rheological, extrusion, and release studies and compared to market vaginal cream Tantum Rosa.

RESULTS

HEC formulations showed good drug release profiles and good rheological behavior but low mucoadhesion strength, whereas NaCMC (4% gel) formulations had better drug release and very high mucoadhesive strength. However, the presence of NaCMC 4% conferred too much viscosity to the preparation. Taking into consideration all performances, the most suitable formulations for vaginal applications resulted in those containing NaCMC (3% gel) and with gel replacing cetostearylic alcohol as they showed good ex vivo performances in terms of manageability and high bioadhesion to vaginal mucosa.

Microemulsion-based vaginal gel of clotrimazole: formulation, in vitro evaluation, and stability studies

The objective of the present investigation was to develop and evaluate microemulsion-based gel for the vaginal delivery of clotrimazole (CMZ). The solubility of CMZ in oils and surfactants was evaluated to identify components of the microemulsion. The ternary diagram was plotted to identify the area of microemulsion existence. Various gelling agents were evaluated for their potential to gel the CMZ microemulsion without affecting its structure. The bioadhesive potential and antifungal activity of the CMZ microemulsion-based gel (CMZ-MBG) was determined in comparison to the marketed clotrimazole gel (Candid-V gel) by in vitro methods. The chemical stability of CMZ in CMZ-MBG was determined as per the International Conference on Harmonization guidelines. The CMZ microemulsion exhibited globule size of 48.4 nm and polydispersity index of 0.75. Carbopol ETD 2020 could successfully gel the CMZ microemulsion without disturbing the structure. The CMZ-MBG showed significantly higher (P < 0.05) in vitro bioadhesion and antifungal activity as compared to that of Candid-V gel. The stability studies indicated that CMZ undergoes acidic pH-catalyzed degradation at all the storage conditions at the end of 3 months.

Heterosexual spread of HIV infection

Sexual transmission is the most common route of spread of human immunodeficiency virus (HIV), with heterosexual transmission of HIV infection accounting for 90% of those infected in 1992 and over 75% of the 10–12 million of those infected to date worldwide. Yet, heterosexual transmission is poorly understood. Since HIV can be transmitted from HIV-infected people who are asymptomatic as well as from those who have the acquired immunodeficiency syndrome (AIDS), we must better define the potential for transmission of HIV from HIV-infected individuals as well as the factors which influence the susceptibility of HIV-uninfected individuals.

Hydrogel nanoparticles in drug delivery

Hydrogel nanoparticles have gained considerable attention in recent years as one of the most promising nanoparticulate drug delivery systems owing to their unique potentials via combining the characteristics of a hydrogel system (e.g., hydrophilicity and extremely high water content) with a nanoparticle (e.g., very small size). Several polymeric hydrogel nanoparticulate systems have been prepared and characterized in recent years, based on both natural and synthetic polymers, each with its own advantages and drawbacks. Among the natural polymers, chitosan and alginate have been studied extensively for preparation of hydrogel nanoparticles and from synthetic group, hydrogel nanoparticles based on poly (vinyl alcohol), poly (ethylene oxide), poly (ethyleneimine), poly (vinyl pyrrolidone), and poly-N-isopropylacrylamide have been reported with different characteristics and features with respect to drug delivery. Regardless of the type of polymer used, the release mechanism of the loaded agent from hydrogel nanoparticles is complex, while resulting from three main vectors, i.e., drug diffusion, hydrogel matrix swelling, and chemical reactivity of the drug/matrix. Several crosslinking methods have been used in the way to form the hydrogel matix structures, which can be classified in two major groups of chemically- and physically-induced crosslinking.

Effect of Excipient and Processing Variables on Adhesive Properties and Release Profile of Pentoxifylline From Mucoadhesive Tablets

The bioavailability and onset of action of drugs with high first-pass metabolism can be significantly improved by administration via the sublingual route. The objective of this study was to evaluate the effect of polymer type and tablet compaction parameters on the adhesive properties and drug release profile from mucoadhesive sublingual tablet formulations. Pentoxifylline was selected as the model drug because it has poor oral bioavailability due to extensive first-pass metabolism. Two polymers known to possess mucoadhesive properties, carbomer and hydroxypropyl methyl cellulose (HPMC), were used to prepare the formulations. Tablets were prepared by using direct compression technique and evaluated for in vitro dissolution, drug-excipient interactions, and adhesive properties. In general, there was a decrease in the rate of drug release with an increase in the concentration of polymers. No drug-excipient interactions were evident from differential scanning calorimetry or high-performance liquid chromatography analysis. For the formulations containing HPMC, the force of mucoadhesion increased with an increase in the concentration of polymer; however, for carbomer formulations, no such correlation was observed. Force of mucoadhesion decreased as a function of hydration time in both of the polymers.

A review of current intravaginal drug delivery approaches employed for the prophylaxis of HIV/AIDS and prevention of sexually transmitted infections

The objective of this review is to describe the current status of several intravaginal anti-HIV microbicidal delivery systems these delivery systems and microbicidal compounds in the context of their stage within clinical trials and their potential cervicovaginal defence successes. The global Human Immuno-Deficiency Virus (HIV) pandemic continues to spread at a rate of more than 15,000 new infections daily and sexually transmitted infections (STIs) can predispose people to acquiring HIV infection. Male-to-female transmission is eight times more likely to occur than female-to-male transmission due to the anatomical structure of the vagina as well as socio-economic factors and the disempowerment of women that renders them unable to refuse unsafe sexual practices in some communities. The increased incidence of HIV in women has identified the urgent need for efficacious and safe intravaginal delivery of anti-HIV agents that can be used and controlled by women. To meet this challenge, several intravaginal anti-HIV microbicidal delivery systems are in the process of been developed. The outcomes of three main categories are discussed in this review: namely, dual-function polymeric systems, non-polymeric systems and nanotechnology-based systems. These delivery systems include formulations that modify the genital environment (e.g. polyacrylic acid gels and lactobacillus gels), surfactants (e.g. sodium lauryl sulfate), polyanionic therapeutic polymers (e.g. carageenan and carbomer/lactic acid gels), proteins (e.g. cyanovirin-N, monoclonal antibodies and thromspondin-1 peptides), protease inhibitors and other molecules (e.g. dendrimer based-gels and the molecular condom). Intravaginal microbicide delivery systems are providing a new option for preventing the transmission of STIs and HIV.

Chronobiology, drug delivery, and chronotherapeutics

Biological processes and functions are organized in space, as a physical anatomy, and time, as a biological time structure. The latter is expressed by short-, intermediate-, and long-period oscillations, i.e., biological rhythms. The circadian (24-h) time structure has been most studied and shows great importance to the practice of medicine and pharmacotherapy of patients. The phase and amplitude of key physiological and biochemical circadian rhythms contribute to the known predictable-in-time patterns in the occurrence of serious and life-threatening medical events, like myocardial infraction and stroke, and the manifestation and severity of symptoms of chronic diseases, like allergic rhinitis, asthma, and arthritis. Moreover, body rhythms can significantly affect responses of patients to diagnostic tests and, most important to the theme of this special issue, medications. Rhythmicity in the pathophysiology of disease is one basis for chronotherapeutics--purposeful variation in time of the concentration of medicines in synchrony with biological rhythm determinants of disease activity--to optimize treatment outcomes. A second basis is the control of undesired effects of medications, especially when the therapeutic range is narrow and the potential for adverse effects high, which is the case for cancer drugs. A third basis is to meet the biological requirements for frequency-modulated drug delivery, which is the case for certain neuroendocrine peptide analogues. Great progress has been realized with hydrogels, and they offer many advantages and opportunities in the design of chronotherapeutic systems for drug delivery via the oral, buccal, nasal, subcutaneous, transdermal, rectal, and vaginal routes. Nonetheless, innovative delivery systems will be necessary to ensure optimal application of chronotherapeutic interventions. Next generation drug-delivery systems must be configurable so they (i) require minimal volitional adherence, (ii) respond to sensitive biomarkers of disease activity that often vary in time as periodic (circadian rhythmic) and non-periodic (random) patterns to release medication to targeted tissue(s) on a real time as needed basis, and (iii) are cost-effective.

Development and in vitro evaluation of a liposomal vaginal delivery system for acyclovir

Design of a liposome delivery system for vaginal administration of acyclovir, able to provide sustained release and improved bioavailability of the encapsulated drug for the local treatment of genital herpes was investigated. Acyclovir was encapsulated in liposomes prepared by the polyol dilution method, whereby various phospholipid compositions were used: egg phosphatidylcholin (PC)/egg phosphatidylglycerol (PG) 9:1, egg phosphatidylcholine (PC) and egg phosphatidycholine (PC)/stearylamine (SA) 9:3. All liposome preparations were characterized and compared for particle size, polydispersity, encapsulation efficiency and tested for in vitro stability in different media chosen to simulate human vaginal conditions: buffer, pH 4.5 (corresponding to normal human vaginal pH), vaginal fluid simulant (medium developed so as to mimic the fluid produced in the vagina) with or without mucin. To be closer to in vivo application of liposomes and to achieve further improvement of their stability, liposomes were incorporated in a vehicle suitable for vaginal self-administration. Bioadhesive hydrogel made from Carbopol 974P NF resin with adequate pH value and desirable viscosity was chosen as a vehicle for liposomes containing acyclovir. In vitro release studies of liposomes incorporated in the hydrogel proved their applicability as a novel vaginal delivery system with localized and sustained release of encapsulated acyclovir. Even after 24 h of incubation in vaginal fluid simulant more than 35% of the originally encapsulated drug was retained in the hydrogel.

Characterisation and in vitro evaluation of bioadhesive liposome gels for local therapy of vaginitis

The purpose of this study was to design and evaluate a new vaginal delivery system for the local treatment of vaginitis. Liposomes containing two commonly applied drugs in the treatment of vaginal infections, namely clotrimazole and metronidazole, were prepared by the proliposome and the polyol dilution methods. Both types of liposomes were characterised and compared for particle size, polydispersity, entrapment efficiency, and tested for in vitro stability in media that mimic human vaginal conditions (buffer, pH 4.5, and vaginal fluid simulant). To achieve application viscosity and to further improve their stability, liposomes containing drugs were incorporated in a bioadhesive gel made of Carbopol 974P NF resin. In vitro release studies have demonstrated that even after 24 h of incubation in vaginal fluid simulant (at 37 degrees C) more than 30% of the originally entrapped clotrimazole (or 50% of metronidazole) was still retained in the gel. Storage stability studies have proved the ability of Carbopol 974P NF gel to preserve original size distributions of incorporated liposomes. All the performed experiments confirm the applicability of bioadhesive liposome gels as a novel delivery system for local therapy of vaginal infections.

The vagina as a route for systemic drug delivery

Exhaustive efforts have been made toward the administration of drugs, via alternative routes, that are poorly absorbed after the oral administration. The vagina as a route of drug delivery has been known since ancient times. In recent years, the vaginal route has been rediscovered as a potential route for systemic delivery of peptides and other therapeutically important macromolecules. However, successful delivery of drugs through the vagina remains a challenge, primarily due to the poor absorption across the vaginal epithelium. The rate and extent of drug absorption after intravaginal administration may vary depending on formulation factors, vaginal physiology, age of the patient and menstrual cycle. Suppositories, creams, gels, tablets and vaginal rings are commonly used vaginal drug delivery systems. The purpose of this communication is to provide the reader with a summary of advances made in the field of vaginal drug delivery. This report, therefore, summarizes various vaginal drug delivery systems with an introduction to vaginal physiology and factors affecting drug absorption from the vaginal route.

Intravaginal gels as drug delivery systems

Recently, there has been a great deal of interest in the design and application of different dosage forms via the vaginal route. Several studies have proven that the vagina is an effective route for drug administration intended mainly for local action, but systemic effects of some drugs also can be attained. The major advantages of this route include accessibility, good blood supply, the ability to bypass first-pass liver metabolism, and permeability to large molecular weight drugs, such as peptides and proteins. Among the delivery systems proposed for this route is the use of intravaginal gels, which have been found to be potential vaginal drug delivery systems. The bioadhesives used in the formulation of gels play a key role in the release of the drug through the attachment to the vaginal mucosa, where the drug diffuses from the gel to the mucus.

Delivery of granulocyte-macrophage colony-stimulating factor in bioadhesive hydrogel stimulates migration of dendritic cells in models of human papillomavirus-associated (pre)neoplastic epithelial lesions

Because of the central role of dendritic cells and/or Langerhans cells(DC/LC) in the induction of cellular immune responses, pharmacological agents that modulate the recruitment of these cells might have a clinical interest. The present study was designed to evaluate the capacity of several pharmaceutical formulations to topically deliver granulocyte-macrophage colony-stimulating factor (GM-CSF) on human papillomavirus (HPV)-associated genital (pre)neoplastic lesions. The formulations were evaluated for their bioactivity and for their potential to recruit DC in organotypic cultures of HPV-transformed keratinocytes. We found that a bioadhesive polycarbophil gel (Noveon) at pH 5.5 is able to maintain the bioactivity of GM-CSF at 4 or 37 degrees C for at least 7 days, whereas a decreased activity of GM-CSF was observed when the molecule is included in other polymer gels. GM-CSF incorporated in the polycarbophil gel was also a potent factor in enhancing the colonization of DC into organotypic cultures of HPV-transformed keratinocytes since the infiltration of DC in the in vitro-formed (pre)neoplastic epithelium was very low under basal conditions and dramatically increased in the presence of GM-CSF gel. We next demonstrated that GM-CSF incorporated in polycarbophil gel induces the recruitment of human DC in a human (pre)neoplastic epithelium grafted into NOD/SCID mice. The efficacy of GM-CSF in this formulation was equivalent to that observed with liquid GM-CSF. These results suggest that GM-CSF incorporated in polycarbophil gel could play an important role in the recruitment of DC/LC in mucosal surfaces and be useful as a new immunotherapeutic approach for genital HPV-associated (pre)neoplastic lesions.

Enzyme immobilization in novel alginate–chitosan core-shell microcapsules

Alginate-chitosan core-shell microcapsules were prepared in order to develop a biocompatible matrix for enzyme immobilization, where the protein is retained either in a liquid or solid core and the shell allows permeability control over substrates and products. The permeability coefficients of different molecular weight compounds (vitamin B2, vitamin B12, and myoglobin) were determined through sodium tripolyphosphate (Na-TPP)-crosslinked chitosan membrane. The microcapsule core was formed by crosslinking sodium alginate with either calcium or barium ions. The crosslinked alginate core was uniformly coated with a chitosan layer and crosslinked with Na-TPP. In the case of calcium alginate, the phosphate ions of Na-TPP were able to extract the calcium ions from alginate and liquefy the core. A model enzyme, beta-galactosidase, was immobilized in the alginate core and the catalytic activity was measured with o-nitrophenyl-beta-D-galactopyranoside (ONPG). Change in the activity of free and immobilized enzyme was determined at three different temperatures. Na-TPP crosslinked chitosan membranes were found to be permeable to solutes of up to 17,000Da molecular weight. The enzyme loading efficiency was higher in the barium alginate core (100%) as compared to the calcium alginate core (60%). The rate of ONPG conversion to o-nitrophenol was faster in the case of calcium alginate-chitosan microcapsules as compared to barium alginate-chitosan microcapsules. Barium alginate-chitosan microcapsules, however, did improve the stability of the enzyme at 37 degrees C relative to calcium alginate-chitosan microcapsules or free enzyme. This study illustrates a new method of enzyme immobilization for biotechnology applications using liquid or solid core and shell microcapsule technology.

Efficacy of a new ketoconazole bioadhesive vaginal tablet on Candida albicans

To develop more effective treatment for vaginal candidasis, ketoconazole (KTZ) was formulated in bioadhesive tablet formulations that increase the time of contact of drug with the vaginal mucosa. The bioadhesive vaginal tablets delivery of KTZ was prepared by direct compression of sodium carboxymethyl cellulose or polyvinylpyrrolidone or hydroxypropylmethyl cellulose (HPMC-E(50)). Dissolution studies of bioadhesive tablets and commercial ovules were carried out with a new basket method (horizontal rotating basket). In vitro, a good sustained release action was obtained with bioadhesive tablets containing 1:1 and 1:2 drug/polymer ratio using HPMC-E(50). These bioadhesive tablets containing 400 mg of KTZ showed a zero-order drug release kinetic. KTZ solutions at increasing concentrations (0.16, 0.33, 0.5 and 0.66 mg/ml) were prepared for microbiological trials. These concentrations correspond to 25%, 50%, 75% and 100% of KTZ released from bioadhesive tablets, respectively. Yeast mixture was mixed with each concentration of KTZ at ratio of 1:10. One hundred microliters of this mixture was transferred in 900 microl liquid Sabouraud medium after a certain time interval for each concentration of KTZ and incubation at 37 degrees C for 24 h. Then this culture streaked onto Sabouraud-dextrose-agar plates, which were incubated at 37 degrees C for 48 h. The 0.16 and 0.33 mg/ml concentrations of KTZ showed fungistatic effect in 120 min. The 0.5 mg/ml concentration of KTZ was fungistatic in 90 and 120 min; and the 0.66 mg/ml concentration of the drug was fungistatic in 120 min as well as in 180 min. It was found that, in vitro antifungal activity of KTZ was dependent on its concentration and contact time with yeast cells. These results indicated that a new bioadhesive vaginal tablet formulations might be further developed for safe convenient and effective treatment of vaginal candidasis.

Effect of buffers on the properties of microbicidal hydrogels containing monoglyceride as the active ingredient

Hydrogel formulations containing the monoglyceride monocaprin have shown potent microbicidal activity against several sexually transmitted viruses and bacteria. It is recommended that formulations for preventing infection in the vagina have a low pH as the HIV virus is inactivated at low pH. The object of the work was to investigate how incorporation of buffers into the hydrogel formulations affects physicochemical properties and microbicidal activity of the active substance. Two series of gels were formulated using carbomer (Carbopol 934) and sodium carboxymethylcellulose (NaCMC) as gel-forming agents. The presence of buffers in the gels caused a lowering in gel viscosity, with carbomer gels being more sensitive to buffer presence than NaCMC gels. To obtain viscosity similar to that of a gel without buffer, the amount of polymer needs to be increased. An increase in the amount of NaCMC by 60-70% is needed to obtain the same viscosity as in gel without buffers; but for carbomer, the amount of polymer needs to be doubled. It appears that the effect of maleate buffer on NaCMC gel formation is greater than that of the citrate/lactate buffer; but for carbopol gels, the effects of the buffer systems tested on gel viscosity were equal. The virucidal activity of NaCMC gel buffered with citrate/lactate buffer against herpes simplex virus type 1 and HIV was not reduced by the presence of buffer. The results show that the presence of buffers in the hydrogel formulations affects gel viscosity, but the virucidal effect of the active compound, monocaprin, is not diminished.

Physical characterization of a chitosan-based hydrogel delivery system

Hydrogel formation from a mixture of biocompatible chitosan, beta-glycerol phosphate, and hydroxyethyl cellulose was studied. The rheological properties of the formed hydrogels were examined using a Bohlin VOR rheometer. The effect of hydrogel composition and temperature on both the gelation rate and the elastic strength of hydrogels was investigated, from which possible hydrogel formation mechanisms were inferred. The formed hydrogels as potential vehicles for delivering pilocarpine were examined. The advantages and disadvantages of chitosan/hydroxyethyl cellulose hydrogel as a delivery system are discussed.

The release of model macromolecules may be controlled by the hydrophobicity of palmitoyl glycol chitosan hydrogels

A non-covalently cross-linked palmitoyl glycol chitosan (GCP) hydrogel has been evaluated as an erodible controlled release system for the delivery of hydrophilic macromolecules. Samples of GCP with hydrophobicity decreasing in the order GCP12>GCP11>GCP21 were synthesised and characterised by 1H NMR. Hydrogels were prepared by freeze-drying an aqueous dispersion of the polymer in the presence or absence of either a model macromolecule fluorescein isothiocyanate-dextran (FITC-dextran, MW 4400), and/or amphiphilic derivatives Gelucire 50/13 or vitamin E d-alpha-tocopherol polyethylene glycol succinate. Gels were analysed for aqueous hydration, FITC-dextran release, and bioadhesion, and imaged by scanning electron microscopy. The gels were highly porous and could be hydrated to up to 95x their original weight without an appreciable volume change and most gels eventually eroded. Hydration and erosion were governed by the hydrophobicity of the gel and the presence of the amphiphilic additives. GCP gels could be loaded with up to 27.5% (w/w) of FITC-dextran by freeze-drying a dispersion of GCP in a solution of FITC-dextran. The controlled release of FITC-dextran was governed by the hydrophobicity of the gel following the trend GCP21>GCP11>GCP12. GCP gels were bioadhesive but less so than hydroxypropylmethylcellulose, Carbopol 974NF (7:3) tablets.

Development of a mucoadhesive dosage form for vaginal administration

The antimycotic imidazole derivative clotrimazole is employed locally for the treatment of genitourinary tract mycotic infections and is formulated as creams, foams, tablets, gels, irrigations, or pessaries. In this study, a new dosage form was developed by including bioadhesive polymers (polycarbophyl, hydroxypropylmethylcellulose, and hyaluronic sodium salt) into pessaries made of semisynthetic solid triglycerides. These polymers hold the delivery systems in the vaginal tract for a few days without any toxic effects or important physiological modifications, prolonging the permanence of the drug on the vaginal mucosa. Technological controls (compatibility with differential scanning calorimetry [DSC] studies, particle size analysis, and liquefaction time test) and biopharmaceutics studies for the evaluation of the release of the drug from the dosage form and of the bioadhesive properties were carried out. Moreover, a new test for the evaluation of the permanence of the drug in a simulated application site was developed from a modification of the Satnikar and Fantelli method for the evaluation of the liquefaction time of rectal suppositories. This test simulates the physiological vaginal condition and verifies the efficiency of the polymers in prolonging the permanence of the dosage form in the location where it is applied. The technological controls demonstrated that the presence of the polymers did not have an influence on the characteristics of the pessaries. On the other hand, there was an improvement in adhesivity of the pessaries in the in vitro adhesion test and prolonging of the liquefaction time in the liquefaction time test in the presence of mucoadhesive polymers, which increased with increasing polymer concentration. The presence of the mucoadhesive had a large influence on the permanence of the drug in the simulated application site because it modified the distribution of the drug along the simulated application site. In conclusion, the developed new formulations showed good technological and adhesion properties and the capacity of hold the dosage form in the target site. Among the employed bioadhesive polymers, the best behavior in the performed test was by polycarbophyl at its maximum concentration.

Liposomal gels for vaginal drug delivery

The aim of our study was to develop a liposomal drug carrier system, able to provide sustained and controlled release of appropriate drug for local vaginal therapy. To optimise the preparation of liposomes with regards to size and entrapment efficiency, liposomes containing calcein were prepared by five different methods. Two optimal liposomal preparations (proliposomes and polyol dilution liposomes) were tested for their in vitro stability in media that simulate human vaginal conditions (buffer, pH 4.5). To be closer to in vivo application of liposomes and to achieve further improvement of their stability, liposomes were incorporated in vehicles suitable for vaginal self-administration. Gels of polyacrylate were chosen as vehicles for liposomal preparations. Due to their hydrophilic nature and bioadhesive properties, it was possible to achieve an adequate pH value corresponding to physiological conditions as well as desirable viscosity. In vitro release studies of liposomes incorporated in these gels (Carbopol 974P NF or Carbopol 980 NF) confirmed their applicability as a novel drug carrier system in vaginal delivery. Regardless of the gel used, even 24 h after the incubation of liposomal gel in the buffer pH 4.5 more than 80% of the originally entrapped substance was still retained.

Development and evaluation of microbicidal hydrogels containing monoglyceride as the active ingredient

A number of medium-chain saturated and long-chain unsaturated fatty acids and their monoglycerides were tested against herpes simplex virus (HSV-1) to determine which lipids were most active during a short incubation time. The aim was to find which lipid would be preferable as the active ingredient in a virucidal hydrogel formulation for the purpose of preventing transmission of pathogens to mucosal membranes, particularly sexually transmitted viruses, such as herpes simplex virus and human immunodeficiency virus (HIV), and bacteria, such as Chlamydia trachomatis and Neisseria gonorrheae. The main strategy was that the formulations would be fast-acting, killing large numbers of virus or bacteria on contact in a short time, preferably causing at least a 10000-fold reduction in virus/bacteria titer in 1-5 min. Monocaprin, the 1-monoglyceride of capric acid, and lauric acid were found to be most active of all the lipids tested, causing a greater than 100000-fold reduction in virus titer in 1 min at a concentration of 20 mM. When tested at a concentration of 10 mM for 1 min, monocaprin was still fully active whereas lauric acid had no or negligible activity. It was concluded that monocaprin was most suitable as the active ingredient in a fast-acting virucidal gel formulation, and several hydrogel formulations containing monocaprin were tested. Formulations where the monoglyceride was dissolved in glycofurol were found to be active against HSV-1. The hydrogel formulations containing 20 mM monocaprin were highly virucidal in vitro and caused a greater than 100000-fold (HSV-1) inactivation of virus in human semen in 1 min. Formulations in dilution 1:10 were cytotoxic in monolayers of CV-1 cells, but they were 10-100 fold less cytotoxic than a commercial product which contains 2% nonoxynol-9.

Development of a "continuous-flow adhesion cell" for the assessment of hydrogel adhesion

The purpose of this study was to develop an in vitro perfusion technique or "continuous-flow adhesion cell" model to predict the in vivo performances of different mucoadhesive drug delivery systems based on hydrogels. Two studies were performed, either using a rabbit small intestine or a polyethylene surface; the adhesion of four gels--two poly(acrylic acid)s (PAAs) (carbomer [CM] and polycarbophil [PC]), an ethyleneoxide-propyleneoxide block copolymer (Poloxamer 407 [PM]), and a polysaccharide (scleroglucane [SG])--were evaluated. In this respect, scleroglucane was used as a control. The adhesiveness of the different gels for both supports is in accordance with that described in the literature, that is, polycarbophil adhered more strongly than carbomer, which itself adhered more strongly than poloxamer. This study proved that the gels adhere more strongly to the polyethylene tube than to the rabbit small intestine, thus indicating that evidence for adhesion properties does not need any presence of mucus. Therefore, our in vitro model could be a good method, more precise and more simple than an ex vivo technique, to predict the bioadhesion of gelified devices.

Drug release and washability of mucoadhesive gels based on sodium carboxymethylcellulose and polyacrylic acid

This study investigated the relationship of the washability of gels based on two mucoadhesive polymers (sodium carboxymethylcellulose [NaCMC] and polyacrylic acid [PAA]) and their mixtures to their physical properties such as consistency and hydration/dissolution. The mucoadhesive properties of the two polymers and the effect of mucus-polymer interaction on gel washability at the mucoadhesive interface were also investigated using mixtures of PAA and NaCMC gels with increasing mucin amounts. Release and wash-away properties of the gels were assessed by means of a simultaneous release and wash-away test, whereas the consistency and hydration/dissolution properties of the gels were investigated by rheological analysis (viscosity and dynamic viscoelastic tests) and liquid uptake measurements, respectively. The results showed that PAA was characterized by lower release and wash-away properties than those of NaCMC. Mixing of two gels at different ratios allowed modulation of the release and wash-away properties. A relationship between washability and hydration/dissolution properties was found. Gel consistency by itself did not always provide a complete explanation of the wash-away process. The two polymers investigated showed different rheological interaction properties with mucin. Depending on the extent of such interaction, gel-mucin mixture had hydration/dissolution and washability properties that were quite different with respect to the initial gel.

A modified Franz diffusion cell for simultaneous assessment of drug release and washability of mucoadhesive gels

A modified Franz cell is proposed to simultaneously measure the amount of drug diffused from semisolid preparations into the receptor chamber and the amount washed away by a tangential buffer stream. Four gels containing acyclovir as model drug and based on hydrophilic polymers (sodium carboxymethylcellulose, methylvinyl ether/maleic anhydride copolymer, methacrylic acid/methacrylic acid methylester copolymer, and polyacrylic acid) were tested. The drug release profiles to the receptor chamber of a standard Franz cell apparatus were obtained and compared to the profiles obtained with the modified apparatus at two buffer stream rates (1.0 and 0.3 ml/min). Some significant differences were observed between the wash-away profiles obtained with the two buffer stream rates. At both flux rates the amount of drug washed away was quite high, and in turn, the drug release profiles to the receptor chamber were lower with respect to those obtained with the standard Franz cell test. The importance of this phenomenon was not the same for all of the polymers: the polyacrylic acid sample, because of the presence of slight crosslinking, was less sensitive to wash away. For all of the other samples, when 1.0 ml/min tangential stream was used, the amount of drug released to the receptor chamber was significantly lower with respect to the standard method. With 0.3 ml/min buffer stream, some significant reduction in release amounts could be observed for the methacrylic acid/methacrylic acid methylester copolymer sample only, which was also the most erodible sample. The method proposed appears suitable to differentiate the examined samples for sensitivity to the washing effect.