Spray drying tenofovir loaded mucoadhesive and pH-sensitive microspheres intended for HIV prevention

Microencapsulation Techniques in HIV Pediatric Formulations: Advances and Future Outlook

The treatment of human immunodeficiency virus (HIV) in children has persistently been complex and tedious on a global scale. This is because adult and pediatric HIV treatments follow a similar therapeutic approach. Due to the dearth of clinically licensed pediatric antiretroviral drug (ARVD) therapy, children with HIV worldwide are prescribed unlicensed drugs each year. This has triggered likelihood of poor drug adherence, therapeutic failure, and even adverse reactions brought on by a variety of factors, including pill size and quantity, which is the main cause of swallowing difficulties, repeated administration of these various ARVDs, many of which have poor solubility and cause severe side effects in children, and unpalatability of the drug, which is one of the criteria for pediatric formulations. Thus, there is a necessity for investigation into several advanced microencapsulation techniques that could curb these challenges. Microencapsulation techniques have explored in drug delivery for encapsulation and manufacture of different nanoparticles that have shown significant potential in mitigating and surmounting different constraints, such as taste masking, enhanced drug solubility and bioavailability, and production of micronized fine powders for treatment of varying diseases. Nevertheless, the usage of these technologies in HIV pediatric formulations has garnered relatively little attention. Thus, this review has paid a keen interest in examining several microencapsulation strategies for potential utilization in the development of HIV pediatric formulations.

Co-emulsified Alginate-Eudragit Nanoparticles: Potential Carriers for Localized and Time-defined Release of Tenofovir in the Female Genital Tract

This research aimed to explore the possibilities of Eudragit S100 (ES100) and sodium alginate as carriers for tenofovir disoproxil fumarate (TDF) in the female genital tract. Alginate and alginate-ES100 nanoparticles were prepared using the ionic gelation and emulsion/gelation complexation method, respectively. The nanocarriers were tested using morphological, physicochemical, in vitro drug release, and cytotoxicity analyses. In SEM and TEM images, the presence of spherical and uniformly distributed nanoparticles was revealed. The FTIR spectrum showed that alginate and calcium chloride interacted due to ionic bonds linking divalent calcium ions and the -COO- of alginate groups. Alginate and ES100 interacted via the ester C=O amide stretching. The results obtained from XRD and DSC, on the other hand, revealed a favorable interaction between sodium alginate and ES100 polymers, as evidenced by the crystallization peaks observed. Under experimental design analysis and optimization, overall size distribution profiles ranged from 134.9 to 228.0 nm, while zeta potential results showed stable nanoparticles (-17.8 to -38.4 MV). The optimal formulation exhibited a maximum cumulative in vitro release of 72% (pH 4.2) up to 96 h. The cytotoxicity tests revealed the safety of TDF-loaded nanoparticles on vaginal epithelial cells at concentrations of 0.025 mg/mL, 0.5 mg/mL, and 1 mg/mL for 72 h. These results indicated that alginate-ES100 nanoparticles have the potential to preserve and sustain the release of the TDF drug in the FGT. The future goal is to develop a low-dose non-toxic microbicide that can be administered long term in the vagina to cater to both pregnant and non-pregnant HIV patients.

pH-triggered polymeric nanoparticles in gel for preventing vaginal transmission of HIV and unintended pregnancy

Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome (HIV/ AIDS) and unplanned pregnancy affect female reproductive health globally. A single product providing a dual purpose of HIV prophylaxis and contraception may improve adherence to the therapy. Thus, we formulated a female-centric multipurpose prevention technology (MPT) comprising of nanoparticle loaded vaginal gel formulation acting as a contraceptive and microbicide. Eudragit® S100 nanoparticles of Atazanavir sulphate (ATZ; antiviral) and Fluoxetine hydrochloride (FLX; repurposed spermicide) were prepared for pH dependent drug release and loaded in carrageenan and HPMC K200M gel. The particle size of ATZ and FLX nanoparticles was 396.7 ± 20.64 nm and 226.5 ± 2.08 nm respectively. The in vitro release of the gel formulation in simulated seminal fluid (pH 7.6) showed 96.16% and 95.98% release of ATZ and FLX respectively at the end of 8 h. The in vitro anti-HIV and spermicidal activity of the formulation was above 80% for low drug concentrations. In vivo studies on murine model showed no signs of inflammation or vaginal epithelial injury. Curcumin based imaging confirmed the retention of the formulation in the reproductive tract of mice with minimal leakage. Nanoparticles in gel enabled non-invasive and localised delivery with minimal side effects and can be an effective prophylactic therapy.

Nanoparticle-based strategies to target HIV-infected cells

Antiretroviral drugs employed for the treatment of human immunodeficiency virus (HIV) infections have remained largely ineffective due to their poor bioavailability, numerous adverse effects, modest uptake in infected cells, undesirable drug-drug interactions, the necessity for long-term drug therapy, and lack of access to tissues and reservoirs. Nanotechnology-based interventions could serve to overcome several of these disadvantages and thereby improve the therapeutic efficacy of antiretrovirals while reducing the morbidity and mortality due to the disease. However, attempts to use nanocarriers for the delivery of anti-retroviral drugs have started gaining momentum only in the past decade. This review explores in-depth the various nanocarriers that have been employed for the treatment of HIV infections highlighting their merits and possible demerits.

Enzyme Responsive Vaginal Microbicide Gels Containing Maraviroc and Tenofovir Microspheres Designed for Acid Phosphatase-Triggered Release for Pre-Exposure Prophylaxis of HIV-1: A Comparative Analysis of a Bigel and Thermosensitive Gel

The challenges encountered with conventional microbicide gels has necessitated the quest for alternative options. This study aimed to formulate and evaluate a bigel and thermosensitive gel, designed to combat the challenges of leakage and short-residence time in the vagina. Ionic-gelation technique was used to formulate maraviroc and tenofovir microspheres. The microspheres were incorporated into a thermosensitive gel and bigel, then evaluated. Enzyme degradation assay was used to assess the effect of the acid phosphatase enzyme on the release profile of maraviroc and tenofovir microspheres. HIV efficacy and cytotoxicity of the microspheres were assessed using HIV-1-BaL virus strain and HeLa cell lines, respectively. Maraviroc and tenofovir release kinetics followed zero-order and Higuchi model kinetics. However, under the influence of the enzyme, maraviroc release was governed by first-order model, while tenofovir followed a super case II transport-mechanism. The altered mode of release and drug transport mechanism suggests a triggered release. The assay of the microspheres suspension on the HeLa cells did not show signs of cytotoxicity. The thermosensitive gel and bigel elicited a progressive decline in HIV infectivity, until at concentrations of 1 μg/mL and 0.1 μg/mL, respectively. The candidate vaginal gels have the potential for a triggered release by the acid phosphatase enzyme present in the seminal fluid, thus, serving as a strategic point to prevent HIV transmission.

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.

Mucoadhesive Microspheres of Maraviroc and Tenofovir Designed for Pre-Exposure Prophylaxis of HIV-1: An in vitro Assessment of the Effect on Vaginal Lactic Acid Bacteria Microflora

Purpose

To formulate and evaluate microspheres of the antiretroviral drugs maraviroc and tenofovir intended for a candidate vaginal microbicide and assess its effect on the vaginal lactic acid bacteria microflora.

Methods

Ionic gelation technique was used to formulate maraviroc and tenofovir microspheres with subsequent characterization. The effect of varying concentrations of the polymer, crosslinking agent and the curing time on the outcome variables viz: particle size, mucoadhesion and encapsulation efficiency were investigated. Lactic acid bacteria were isolated from the vagina of healthy women using standard microbiologic methods. The analysis of their 16S rRNA sequence data identified Lactobacillus fermentum and Enterococcus faecalis strains which were assigned GenBank accession numbers. The efficacy of the microspheres on HIV-1BaL strain was evaluated using TZM-bl indicator cells.

Results

The optimal maraviroc and tenofovir microspheres had particle sizes of (434.82 µm and 456.18 µm), mucoadhesion of (93.3% and 90%) and encapsulation efficiency (92.80% and 78.9%) respectively. Maraviroc release kinetics followed a zero-order model and tenofovir was released via Higuchi model. The assay of a 1 mg/mL suspension of the microspheres on the strains of Lactobacillus fermentum and Enterococcus faecalis showed a viability of 93.9% and 89.7%, respectively. There was a statistically significant difference between the mean absorbance readings of the test agent and that of the positive control (P = 0.001). The microspheres elicited a progressive decline in HIV infectivity until at a concentration of 1 μg/mL.

Conclusion

The antiretroviral drugs loaded in the microspheres, had good mucoadhesion which is a potential for prolonged residence time in the vagina. The antiretroviral drugs were adequately released from the microspheres and showed efficacy against the HIV-1 BaL virus strain. There was no significant disruption in the growth of the lactic acid bacteria which constitute valuable bacteria microflora of the vagina.

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Smart Freeze-Dried Bigels for the Prevention of the Sexual Transmission of HIV by Accelerating the Vaginal Release of Tenofovir during Intercourse

Sub-Saharan African women are still at risk from the human immunodeficiency virus (HIV), and sex with men is the main route of transmission. Vaginal formulations containing antiretroviral drugs are promising tools to give women the power to protect themselves. The aim of this work was to obtain freeze-dried bigels containing pectin, chitosan, or hypromellose for the vaginal controlled release of Tenofovir, which is accelerated in the presence of semen. Nine batches of bigels were formulated using different proportions of these polymers in the hydrogel (1, 2, and 3% w/w). The bigels obtained were freeze-dried and then underwent hardness and deformability, mucoadhesion, swelling, and drug release tests, the last two in simulated vaginal fluid (SVF) and SVF/simulated seminal fluid (SSF) mixture. The formulation containing 3% pectin (fd3P) has the highest values for hardness, resistance to deformation, and good mucoadhesivity. Its swelling is conditioned by the pH of the medium, which is responsive to the controlled release of Tenofovir in SVF, with the fastest release in the SVF/SSF mixture. fd3P would be an interesting smart microbicidal system to allow faster release of Tenofovir in the presence of semen, and thus increase women’s ability to protect themselves from the sexual transmission of HIV.

Tenofovir Hot-Melt Granulation using Gelucire® to Develop Sustained-Release Vaginal Systems for Weekly Protection against Sexual Transmission of HIV

Hot-melt granulation is a technique used to obtain granules by dispersing a drug in polymers at a high temperature. Tenofovir, an antiretroviral drug with proven activity as a vaginal microbicide, was dispersed in melted Gelucire® (or a mixture of different Gelucire®) to obtain drug-loaded granules. Studies performed on the granules proved that the drug is not altered in the hot-melt granulation process. The granules obtained were included in a matrix formed by the hydrophilic polymers hydroxypropylmethylcellulose and chitosan to obtain vaginal tablets that combine different mechanisms of controlled release: The Gelucire® needs to soften to allow the release of the Tenofovir, and the hydrophilic polymers must form a gel so the drug can diffuse through it. The studies performed with the tablets were swelling behavior, Tenofovir release, and ex vivo mucoadhesion. The tablets containing granules obtained with Tenofovir and Gelucire® 43/01 in a ratio of 1:2 in a matrix formed by hydroxypropylmethylcellulose and chitosan in a ratio of 1.9:1 were selected as the optimal formulation, since they release Tenofovir in a sustained manner over 216h and remain attached to the vaginal mucosa throughout. A weekly administration of these tablets would therefore offer women protection against the sexual transmission of HIV.

Chitosan-Based Mucoadhesive Vaginal Tablets for Controlled Release of the Anti-HIV Drug Tenofovir

Vaginal microbicides have the potential to give women at high risk of contracting HIV the option of self-protection by preventing the sexual transmission of the virus. In this paper, mucoadhesive vaginal tablets based on chitosan, alone and in combination with pectin and locust bean gum, were developed for the sustained release of tenofovir (an antiretroviral drug). The formulations were placed in simulant vaginal fluid (SVF) to swell, and Hg porosity and SEM microscopy were used for the microstructural characterization of the swelling witnesses. The results show that the association of pectin and chitosan generated polyelectrolyte complexes and produced a robust system able to maintain its structure during the swelling process, when small pores are formed. Drug release and bovine vaginal mucoadhesion studies were performed in SVF showing that tenofovir-controlled dissolution profiles and adhesion to the mucosa were conditioned by the swelling processes of the polymer/s in each formulation. Tablets based on chitosan/pectin have the most homogeneous tenofovir dissolution profiles and last up to 96 h, remaining attached to the vaginal mucosa for the same period. These formulations can therefore be considered a good option for the self-protection of women from the sexual transmission of HIV.

Pharmaceutical Approaches to HIV Treatment and Prevention

Human immunodeficiency virus (HIV) infection continues to pose a major infectious disease threat worldwide. It is characterized by the depletion of CD4+ T cells, persistent immune activation, and increased susceptibility to secondary infections. Advances in the development of antiretroviral drugs and combination antiretroviral therapy have resulted in a remarkable reduction in HIV-associated morbidity and mortality. Antiretroviral therapy (ART) leads to effective suppression of HIV replication with partial recovery of host immune system and has successfully transformed HIV infection from a fatal disease to a chronic condition. Additionally, antiretroviral drugs have shown promise for prevention in HIV pre-exposure prophylaxis and treatment as prevention. However, ART is unable to cure HIV. Other limitations include drug-drug interactions, drug resistance, cytotoxic side effects, cost, and adherence. Alternative treatment options are being investigated to overcome these challenges including discovery of new molecules with increased anti-viral activity and development of easily administrable drug formulations. In light of the difficulties associated with current HIV treatment measures, and in the continuing absence of a cure, the prevention of new infections has also arisen as a prominent goal among efforts to curtail the worldwide HIV pandemic. In this review, the authors summarize currently available anti-HIV drugs and their combinations for treatment, new molecules under clinical development and prevention methods, and discuss drug delivery formats as well as associated challenges and alternative approaches for the future.

pH-responsive delivery of Griffithsin from electrospun fibers

Human immunodeficiency virus (HIV-1) affects over 36 million people globally. Current prevention strategies utilize antiretrovirals that have demonstrated protection, but result in antiviral resistance, adverse toxicity, and require frequent administration. A novel biologic, griffithsin (GRFT), has demonstrated outstanding safety and efficacy against laboratory and primary HIV isolates and against intravaginal murine herpes simplex virus 2 (HSV-2) challenge, making it a promising microbicide candidate. However, transient activity and instability remain concerns surrounding biologic delivery, particularly in the harsh environment of the female reproductive tract (FRT). Recently, electrospun fibers (EFs) have demonstrated promise for intravaginal delivery, with the potential to conserve active agent until release is needed. The goal of this study was to fabricate and characterize pH-responsive fibers comprised of poly(lactic-co-glycolic acid) (PLGA) or methoxypolyethylene glycol-b-PLGA (mPEG-PLGA) with varying ratios of poly(n-butyl acrylate-co-acrylic acid) (PBA-co-PAA), to selectively release GRFT under pH-conditions that mimic semen introduction. Fibers comprised of mPEG-PLGA:PBA-co-PAA (90:10 w/w) demonstrated high GRFT loading that was maintained within simulated vaginal fluid (SVF), and pH-dependent release upon exposure to buffered and SVF:simulated semen solutions. Moreover, GRFT fibers demonstrated potent in vitro efficacy against HIV-1 and safety in vaginal epithelial cells, suggesting their future potential for efficacious biologic delivery to the FRT.

Design and in vitro evaluation of tenofovir-loaded vaginal gels for the prevention of HIV infections

Infection with the human immunodeficiency virus (HIV) is affecting women disproportionally with increasing incidence rates over the last decades. Tenofovir is one of the most commonly used antiretroviral agents, which belongs to the nucleoside/nucleotide reverse transcriptase inhibitor family, for the prevention of HIV acquisition. In scope of this study, a thermogelling system containing tenofovir-loaded chitosan nanoparticles for the controlled release of tenofovir was developed and characterized. The in vitro release studies have shown that the burst release effect was decreased to 27% with f-TFV CS NPs-Gel. Gelation temperature of developed formulation was found as 26.6 ± 0.2 °C, which provides ease of administration while gelation occurs after the administration to the vagina. The work of adhesion values was used as parameters for comparison of mucoadhesive performance and the mucoadhesion of f-TFV CS NPs-Gel was found as 0.516 ± 0.136 N.s at 37 °C. The biocompatibility of blank formulations was evaluated by cell viability studies using L929 cells, in which Gel + CS NPs formulation was found to be safe with 82.4% and 90.2% cell viability for 1:16 and 1:32 dilutions, respectively. In conclusion, an improved tenofovir containing vaginal gel formulation was successfully developed and evaluated for preventing HIV transmission.

Spray-Dried Thiolated Chitosan-Coated Sodium Alginate Multilayer Microparticles for Vaginal HIV Microbicide Delivery

It is hypothesized that novel thiolated chitosan-coated multilayer microparticles (MPs) with enhanced drug loading are more mucoadhesive than uncoated MPs and safe in vivo for vaginal delivery of topical anti-HIV microbicide. Formulation optimization is achieved through a custom experimental design and the alginate (AG) MPs cores are prepared using the spray drying method. The optimal MPs are then coated with the thiolated chitosan (TCS) using a layer-by-layer method. The morphological analysis, in situ drug payload, in vitro drug release profile, and mucoadhesion potential of the MPs are carried out using scanning electron microscopy, solid-state ³¹P NMR spectroscopy, UV spectroscopy, fluorescence imaging and periodic acid Schiff method, respectively. The cytotoxicity and preclinical safety of MPs are assessed on human vaginal (VK2/E6E7) and endocervical (End1/E6E7) epithelial cell lines and in female C57BL/6 mice, respectively. The results show that the MPs are successfully formulated with an average diameter ranging from 2 to 3 μm with a drug loading of 7-12% w/w. The drug release profile of these MPs primarily follows the Baker-Lonsdale and Korsmeyer-Peppas models. The MPs exhibit high mucoadhesion (20-50 folds) compared to native AGMPs. The multilayer MPs are noncytotoxic. Histological and immunochemical analysis of the mice genital tract shows neither signs of damage nor inflammatory cell infiltrate. These data highlight the potential use of TCS-coated AG-based multilayer MPs templates for the topical vaginal delivery of anti-HIV/AIDS microbicides.

Nanocarrier fabrication and macromolecule drug delivery: challenges and opportunities

Macromolecules (proteins/peptides) have the potential for the development of new therapeutics. Due to their specific mechanism of action, macromolecules can be administered at relatively low doses compared with small-molecule drugs. Unfortunately, the therapeutic potential and clinical application of macromolecules is hampered by various obstacles including their large size, short in vivo half-life, phagocytic clearance, poor membrane permeability and structural instability. These challenges have encouraged researchers to develop novel strategies for effective delivery of macromolecules. In this review, various routes of macromolecule administration (invasive/noninvasive) are discussed. The advantages/limitations of novel delivery systems and the potential role of nanotechnology for the delivery of macromolecules are elaborated. In addition, fabrication approaches to make nanoformulations in different shapes and sizes are also summarized.

Tenofovir Containing Thiolated Chitosan Core/Shell Nanofibers: In Vitro and in Vivo Evaluations

It is hypothesized that thiolated chitosan (TCS) core/shell nanofibers (NFs) can enhance the drug loading of tenofovir, a model low molecular weight and highly water-soluble drug molecule, and improve its mucoadhesivity and in vivo safety. To test this hypothesis, poly(ethylene oxide) (PEO) core with TCS and polylactic acid (PLA) shell NFs are fabricated by a coaxial electrospinning technique. The morphology, drug loading, drug release profiles, cytotoxicity and mucoadhesion of the NFs are analyzed using scanning and transmission electron microscopies, liquid chromatography, cytotoxicity assays on VK2/E6E7 and End1/E6E7 cell lines and Lactobacilli crispatus, fluorescence imaging and periodic acid colorimetric method, respectively. In vivo safety studies are performed in C57BL/6 mice followed by H&E and immunohistochemical (CD45) staining analysis of genital tract. The mean diameters of PEO, PEO/TCS, and PEO/TCS-PLA NFs are 118.56, 9.95, and 99.53 nm, respectively. The NFs exhibit smooth surface. The drug loading (13%-25%, w/w) increased by 10-fold compared to a nanoparticle formulation due to the application of the electrospinning technique. The NFs are noncytotoxic at the concentration of 1 mg/mL. The PEO/TCS-PLA core/shell NFs mostly exhibit a release kinetic following Weibull model (r² = 0.9914), indicating the drug release from a matrix system. The core/shell NFs are 40-60-fold more bioadhesive than the pure PEO based NFs. The NFs are nontoxic and noninflammatory in vivo after daily treatment for up to 7 days. Owing to their enhanced drug loading and preliminary safety profile, the TCS core/shell NFs are promising candidates for the topical delivery of HIV/AIDS microbicides such as tenofovir.

Novel Spray Dried Glycerol 2-Phosphate Cross-Linked Chitosan Microparticulate Vaginal Delivery System-Development, Characterization and Cytotoxicity Studies

Chitosan microparticulate delivery systems containing clotrimazole were prepared by a spray drying technique using glycerol 2-phosphate as an ion cross-linker. The impact of a cross-linking ratio on microparticle characteristics was evaluated. Drug-free and drug-loaded unmodified or ion cross-linked chitosan microparticles were examined for the in vitro cytotoxicity in VK2/E6E7 human vaginal epithelial cells. The presence of glycerol 2-phosphate influenced drug loading and encapsulation efficacy in chitosan microparticles. By increasing the cross-linking ratio, the microparticles with lower diameter, moisture content and smoother surface were observed. Mucoadhesive studies displayed that all formulations possessed mucoadhesive properties. The in vitro release profile of clotrimazole was found to alter considerably by changing the glycerol 2-phosphate/chitosan ratio. Results from cytotoxicity studies showed occurrence of apoptotic cells in the presence of chitosan and ion cross-linked chitosan microparticles, followed by a loss of membrane potential suggesting that cell death might go through the mitochondrial apoptotic pathway.

Development and characterization of a long-acting nanoformulated abacavir prodrug

AIM

A myristoylated abacavir (ABC) prodrug was synthesized to extend drug half-life and bioavailability.

METHODS

Myristoylated ABC (MABC) was made by esterifying myristic acid to the drug's 5-hydroxy-cyclopentene group. Chemical composition, antiretroviral activity, cell uptake and retention and cellular trafficking of free MABC and poloxamer nanoformulations of MABC were assessed by proton nuclear magnetic resonance and tested in human monocyte-derived macrophages. Pharmacokinetics of ABC and nanoformulated MABC were evaluated after intramuscular injection into mice.

RESULTS

MABC antiretroviral activity in monocyte-derived macrophages was comparable to native drug. Encasement of MABC into poloxamer nanoparticles extended drug bioavailability for 2 weeks.

CONCLUSION

MABC synthesis and encasement in polymeric nanoformulations improved intracellular drug accumulation and demonstrate translational potential as part of a long-acting antiretroviral regimen.

Recent progresses in bioadhesive microspheres via transmucosal administration

Based on the advantages of adhesion preparations and the application status of microspheres (MSs) in mucous delivery, this paper primarily reviews the bioadhesive MSs via transmucosal administration routes, including the mucosa in alimentary tract and other lumens. Particularly, the detailed researches about of celladhesive MSs and some new-style bioadhesive MSs are mentioned. Furthermore, this review attempts to reveal the advances of bioadhesive MSs as cell-selective bioadhesion systems and the stimuli-responsive MSs as location-specific drug delivery systems. Although these MSs show powerful strength, some far-sighted ideas should be brought on agendas. In the future, mechanisms should be put under tight scrutiny and more attention should be focused on the excellent bioadhesive materials and the 'second generation mucoadhesives'. Meaningful clinical applications of these novel MSs are also of current concerns and need more detailed researches.

Advantages and challenges of the spray-drying technology for the production of pure drug particles and drug-loaded polymeric carriers

Spray-drying is a rapid, continuous, cost-effective, reproducible and scalable process for the production of dry powders from a fluid material by atomization through an atomizer into a hot drying gas medium, usually air. Often spray-drying is considered only a dehydration process, though it also can be used for the encapsulation of hydrophilic and hydrophobic active compounds within different carriers without substantial thermal degradation, even of heat-sensitive substances due to fast drying (seconds or milliseconds) and relatively short exposure time to heat. The solid particles obtained present relatively narrow size distribution at the submicron-to-micron scale. Generally, the yield% of spray-drying at laboratory scale with conventional spray-dryers is not optimal (20-70%) due to the loss of product in the walls of the drying chamber and the low capacity of the cyclone to separate fine particles (<2 μm). Aiming to overcome this crucial drawback in early development stages, new devices that enable the production of submicron particles with high yield, even for small sample amounts, have been introduced into the market. This review describes the most outstanding advantages and challenges of the spray-drying method for the production of pure drug particles and drug-loaded polymeric particles and discusses the potential of this technique and the more advanced equipment to pave the way toward reproducible and scalable processes that are critical to the bench-to-bedside translation of innovative pharmaceutical products.

Stimulus-responsive hydrogels: Theory, modern advances, and applications

Over the past century, hydrogels have emerged as effective materials for an immense variety of applications. The unique network structure of hydrogels enables very high levels of hydrophilicity and biocompatibility, while at the same time exhibiting the soft physical properties associated with living tissue, making them ideal biomaterials. Stimulus-responsive hydrogels have been especially impactful, allowing for unprecedented levels of control over material properties in response to external cues. This enhanced control has enabled groundbreaking advances in healthcare, allowing for more effective treatment of a vast array of diseases and improved approaches for tissue engineering and wound healing. In this extensive review, we identify and discuss the multitude of response modalities that have been developed, including temperature, pH, chemical, light, electro, and shear-sensitive hydrogels. We discuss the theoretical analysis of hydrogel properties and the mechanisms used to create these responses, highlighting both the pioneering and most recent work in all of these fields. Finally, we review the many current and proposed applications of these hydrogels in medicine and industry.

Protein and oligonucleotide delivery systems for vaginal microbicides against viral STIs

Intravaginal delivery offers an effective option for localized, targeted, and potent microbicide delivery. However, an understanding of the physiological factors that impact intravaginal delivery must be considered to develop the next generation of microbicides. In this review, a comprehensive discussion of the opportunities and challenges of intravaginal delivery are highlighted, in the context of the intravaginal environment and currently utilized dosage forms. After a subsequent discussion of the stages of microbicide development, the intravaginal delivery of proteins and oligonucleotides is addressed, with specific application to HSV and HIV. Future directions may include the integration of more targeted delivery modalities to virus and host cells, in addition to the use of biological agents to affect specific genes and proteins involved in infection. More versatile and multipurpose solutions are envisioned that integrate new biologicals and materials into potentially synergistic combinations to achieve these goals.

Evaluation of degradation kinetics and physicochemical stability of tenofovir

Tenofovir (TFV) has been proven to prevent the transmission of the Human Immunodeficiency Virus (HIV) through the vagina. But, there is little information available about its stability under various storage and stress conditions. Hence, this study aimed to investigate the degradation behavior and physicochemical stability of TFV using liquid chromatography coupled mass spectrometry (LC-MS) and solid state X-ray diffraction (XRD) analyses. The LC-MS analysis was performed on a QTrap mass spectrometer with an enhanced mass spectrum (EMS) scan in positive mode. A reversed phase C18 column was used as the stationary phase. TFV exhibited degradation under acidic and alkaline hydrolytic conditions. The degradation products with m/z 289.2 and 170 amu have been proposed as 6-Hydroxy adenine derivative of TFV, and (2-hydroxypropan-2-yloxy) methylphosphonic acid, respectively. A pseudo-first-order degradation kinetic allowed for estimating the shelf-life, half-life, and time required for 90% degradation of 3.84, 25.34, and 84.22 h in acidic conditions, and 58.26, 384.49, and 1277.75 h in alkaline conditions, respectively. No significant degradation was observed at pH 4.5 (normal cervicovaginal pH) and oxidative stress conditions of 3% and 30% v/v hydrogen peroxide solutions. The shelf life of TFV powder at room temperature was 23 months as calculated by using an Arrhenius plot. The XRD pattern showed that the drug was stable and maintained its original crystallinity under the accelerated and thermal stress conditions applied. Stability analyses revealed that the TFV was stable in various stress conditions; however, formulation strategies should be implemented to protect it in strong acidic and alkaline environments.

Microbicides for the Treatment of Sexually Transmitted HIV Infections

Approximately 34 million people were living with human immunodeficiency virus (HIV-1) at the end of 2011. From the last two decades, researchers are actively involved in the development of an effective HIV-1 treatment, but the results intended are still doubtful about the eradication of HIV. The HIV-1 virus has gone from being an "inherently untreatable" infectious agent to the one liable to be affected by a range of approved therapies. Candidate microbicides have been developed to target specific steps in the process of viral transmission. Microbicides are self-administered agents that can be applied to vaginal or rectal mucosal surfaces with the aim of preventing, or reducing, the transmission of sexually transmitted infections (STIs) including HIV-1. The development of efficient, widely available, and low-cost microbicides to prevent sexually transmitted HIV infections should be given high priority. In this review, we studied the various forms of microbicides, their mechanism of action, and their abundant approaches to control the transmission of sexually transmitted infections (STIs).

Hyaluronidase-sensitive nanoparticle templates for triggered release of HIV/AIDS microbicide in vitro

This study was designed to test the hypothesis that a triggered release of a topical microbicide (tenofovir) from hyaluronic acid nanoparticles (HA-NPs) can be achieved under the influence of hyaluronidase (HAase) enzyme. A fractional factorial experimental design was used to examine the factors [molar concentrations of adipic acid dihydrazide (X1) and 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride (X2), volume of acetone (X3) and reaction time (X4)] influencing the responses, Y1; particle mean diameter: PMD (nanometers: nm), Y2; polydispersity index: PDI and Y3; zeta (ζ) potential: (millivolts). The amide bond formation between HA and ADH after cross-linking was confirmed by FT-IR and (13)C-NMR analyses. These NPs were also characterized for cytotoxicity on a human vaginal epithelial cell line and L. crispatus. When formulated with factors X1; 2.49 mM, X2; 9.96 mM, X3; 60 mL, X4; 6 h, HA-NPs exhibited a spherical shape with PMD, PDI, ζ potential, encapsulation efficiency, and drug loading of 70.6 ± 4.1 nm, 0.07 ± 0.02, -38.2 ± 2.8 mV, 51.8 ± 2.4% w/w and 26.1 ± 1.2% w/w, respectively, (n = 3). Unlike for HA based gel, HAase significantly triggered the drug release and HA degradation from the NPs after 24 h (~90% w/w and 65% w/w, respectively); whereas, in its absence, these values were ~39% w/w and 26% w/w, respectively. The NPs were non-cytotoxic to human vaginal VK2/E6E7, End1/E6E7 cells and Lactobacillus crispatus. These data highlight the potential of HAase-sensitive HA-NPs templates for the controlled and vaginal delivery of anti-HIV/AIDS microbicides.

Osmotic pump tablets for delivery of antiretrovirals to the vaginal mucosa

Vaginal pre-exposure prophylaxis has focused heavily on gel formulations. Low adherence linked with frequent dosing and short therapeutic duration has emerged as the major reason for inconsistent efficacy outcomes with gels in clinical trials. Osmotic pumps can achieve versatile drug release profiles however, have not been explored for vaginal delivery. In this report, we describe an osmotic pump tablet (OPT) that can deliver antiretrovirals for several days. We also describe configuring the OPT for pH sensitive delivery where the drug delivery system consistently delivers an antiretroviral at vaginal pH and then gives a burst release triggered by a coitally associated pH increase. We have investigated the vaginal OPT for multiple day delivery of a potent antiretroviral, IQP-0528 in a sheep model. To effectively register spatial drug distribution we also engineered a tool to precisely collect multiple vaginal fluid samples. In a 10-day duration post single application, high micromolar mucosal levels were obtained with peak concentration more than 6 logs higher than the EC50 of IQP-0528. Overall, our results show successful implementation of the osmotic pump technology for vaginal antiretroviral delivery.