Formulating a sulfonated antiviral dendrimer in a vaginal microbicidal gel having dual mechanisms of action

Progresses in Nano-Enabled Platforms for the Treatment of Vaginal Disorders

BACKGROUND

The most common vaginal disorders are within the uterus. According to the latest statistics, vaginal disorders occur in 50% to 60% of females. Although curative treatments rely on surgical therapy, still first-line treatment is a non invasive drug. Conventional therapies are available in the oral and parenteral route, leading to nonspecific targeting, which can cause dose-related side effects. Vaginal disorders are localized uterine disorders in which intrauterine delivery via the vaginal site is deemed the preferable route to mitigate clinical drug delivery limitations.

OBJECTIVE

This study emphasizes the progress of site-specific and controlled delivery of therapeutics in the treatment of vaginal disorders and systemic adverse effects as well as the therapeutic efficacy.

METHODS

Related research reports and patents associated with topics are collected, utilized, and summarized the key findings.

RESULTS

The comprehensive literature study and patents like (US 9393216 B2), (JP6672370B2), and (WO2018041268A1) indicated that nanocarriers are effective above traditional treatments and have some significant efficacy with novelty.

CONCLUSION

Nowadays, site-specific and controlled delivery of therapeutics for the treatment of vaginal disorders is essential to prevent systemic adverse effects and therapeutic efficacy would be more effective. Nanocarriers have therefore been used to bypass the problems associated with traditional delivery systems for the vaginal disorder.

Peptides to Overcome the Limitations of Current Anticancer and Antimicrobial Nanotherapies

Biomedical research devotes a huge effort to the development of efficient non-viral nanovectors (NV) to improve the effectiveness of standard therapies. NVs should be stable, sustainable and biocompatible and enable controlled and targeted delivery of drugs. With the aim to foster the advancements of such devices, this review reports some recent results applicable to treat two types of pathologies, cancer and microbial infections, aiming to provide guidance in the overall design of personalized nanomedicines and highlight the key role played by peptides in this field. Additionally, future challenges and potential perspectives are illustrated, in the hope of accelerating the translational advances of nanomedicine.

Baseline and time-updated factors in preclinical development of anionic dendrimers as successful anti-HIV-1 vaginal microbicides

Although a wide variety of topical microbicides provide promising in vitro and in vivo efficacy, most of them failed to prevent sexual transmission of human immunodeficiency virus type 1 (HIV‐1) in human clinical trials. In vitro, ex vivo, and in vivo models must be optimized, considering the knowledge acquired from unsuccessful and successful clinical trials to improve the current gaps and the preclinical development protocols. To date, dendrimers are the only nanotool that has advanced to human clinical trials as topical microbicides to prevent HIV‐1 transmission. This fact demonstrates the importance and the potential of these molecules as microbicides. Polyanionic dendrimers are highly branched nanocompounds with potent activity against HIV‐1 that disturb HIV‐1 entry. Herein, the most significant advancements in topical microbicide development, trying to mimic the real‐life conditions as closely as possible, are discussed. This review also provides the preclinical assays that anionic dendrimers have passed as microbicides because they can improve current antiviral treatments' efficacy.

This article is categorized under:

Nanotechnology Approaches to Biology > Nanoscale Systems in Biology

Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease

Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine

Antiviral Polymers: A Review

Polymers, due to their high molecular weight, tunable architecture, functionality, and buffering effect for endosomal escape, possess unique properties as a carrier or prophylactic agent in preventing pandemic outbreak of new viruses. Polymers are used as a carrier to reduce the minimum required dose, bioavailability, and therapeutic effectiveness of antiviral agents. Polymers are also used as multifunctional nanomaterials to, directly or indirectly, inhibit viral infections. Multifunctional polymers can interact directly with envelope glycoproteins on the viral surface to block fusion and entry of the virus in the host cell. Polymers can indirectly mobilize the immune system by activating macrophages and natural killer cells against the invading virus. This review covers natural and synthetic polymers that possess antiviral activity, their mechanism of action, and the effect of material properties like chemical composition, molecular weight, functional groups, and charge density on antiviral activity. Natural polymers like carrageenan, chitosan, fucoidan, and phosphorothioate oligonucleotides, and synthetic polymers like dendrimers and sialylated polymers are reviewed. This review discusses the steps in the viral replication cycle from binding to cell surface receptors to viral-cell fusion, replication, assembly, and release of the virus from the host cell that antiviral polymers interfere with to block viral infections.

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.

Peptides and Dendrimers: How to Combat Viral and Bacterial Infections

The alarming growth of antimicrobial resistance and recent viral pandemic events have enhanced the need for novel approaches through innovative agents that are mainly able to attach to the external layers of bacteria and viruses, causing permanent damage. Antimicrobial molecules are potent broad-spectrum agents with a high potential as novel therapeutics. In this context, antimicrobial peptides, cell penetrating peptides, and antiviral peptides play a major role, and have been suggested as promising solutions. Furthermore, dendrimers are to be considered as suitable macromolecules for the development of advanced nanosystems that are able to complement the typical properties of dendrimers with those of peptides. This review focuses on the description of nanoplatforms constructed with peptides and dendrimers, and their applications.

In vitro anti-inflammatory potential of phloretin microemulsion as a new formulation for prospective treatment of vaginitis

Phloretin is a promising polyphenolic compound known for its anti-inflammatory properties, but its poor solubility and low bioavailability hinder its clinical applicability. Till current date, its potential in the treatment of vaginitis has not been explored, and only very few papers reported its formulation as nanoparticles to overcome its pharmaceutical challenges. Therefore, in the current study, phloretin was formulated in microemulsion of 11 nm size, and its in vitro anti-inflammatory properties were explored using histamine and IL-6 release inhibition assays, protease inhibition assay, and membrane stabilization potential. The anti-inflammatory properties of phloretin microemulsion were compared to the drug phloretin, and the reference standard non-steroidal anti-inflammatory drugs (NSAIDs). Results proved that both phloretin and phloretin microemulsion significantly inhibited the release of the inflammatory mediators histamine and IL-6, inhibited protease action, and exhibited membrane stabilization potential. Phloretin microemulsion exhibited comparable anti-inflammatory properties to the NSAIDs diclofenac and indomethacin, and, hence, it can be delineated as a promising therapeutic tool in topical treatment of vaginal inflammation.

Dendrimers in the context of nanomedicine

Dendrimers are globular structures, presenting an initiator core, repetitive layers starting radially from the core and terminal groups on the surface, resembling tree architecture. These structures have been studied in many biological applications, as drug, DNA, RNA and proteins delivery, as well as imaging and radiocontrast agents. With reference to that, this review focused in providing examples of dendrimers used in nanomedicine. Although most studies emphasize cancer, there are others which reveal action in the neurosystem, reducing either neuroinflammation or protein aggregation. Dendrimers can carry bioactive compounds by covalent bond (dendrimer prodrug), or by ionic interaction or adsortion in the internal space of the nanostructure. Additionally, dendrimers can be associated with other polymers, as PEG (polyethylene glycol), and with targeting structures as aptamers, antibodies, folic acid and carbohydrates. Their products in preclinical/clinical trial and those in the market are also discussed, with a total of six derivatives in clinical trials and seven products available in the market.

Designer Peptide and Protein Dendrimers: A Cross-Sectional Analysis

Dendrimers have attracted immense interest in science and technology due to their unique chemical structure that offers a myriad of opportunities for researchers. Dendritic design allows us to present peptides in a branched three-dimensional fashion that eventually leads to a globular shape, thus mimicking globular proteins. Peptide dendrimers, unlike other classes of dendrimers, have immense applications in biomedical research due to their biological origin. The diversity of potential building blocks and innumerable possibilities for design, along with the fact that the area is relatively underexplored, make peptide dendrimers sought-after candidates for various applications. This review summarizes the stepwise evolution of peptidic dendrimers along with their multifaceted applications in various fields. Further, the introduction of biomacromolecules such as proteins to a dendritic scaffold, resulting in complex macromolecules with discrete molecular weights, is an altogether new addition to the area of organic chemistry. The synthesis of highly complex and fully folded biomacromolecules on a dendritic scaffold requires expertise in synthetic organic chemistry and biology. Presently, there are only a handful of examples of protein dendrimers; we believe that these limited examples will fuel further research in this area.

Nanomedicine in the development of anti-HIV microbicides

Prevention plays an invaluable role in the fight against HIV/AIDS. The use of microbicides is considered an interesting potential approach for topical pre-exposure prophylaxis of HIV sexual transmission. The prospects of having an effective product available are expected to be fulfilled in the near future as driven by recent and forthcoming results of clinical trials. Different dosage forms and delivery strategies have been proposed and tested for multiple microbicide drug candidates presently at different stages of the development pipeline. One particularly interesting approach comprises the application of nanomedicine principles to the development of novel anti-HIV microbicides, but its implications to efficacy and safety are not yet fully understood. Nanotechnology-based systems, either presenting inherent anti-HIV activity or acting as drug nanocarriers, may significantly influence features such as drug solubility, stability of active payloads, drug release, interactions between active moieties and virus/cells, intracellular drug delivery, drug targeting, safety, antiviral activity, mucoadhesive behavior, drug distribution and tissue penetration, and pharmacokinetics. The present manuscript provides a comprehensive and holistic overview of these topics as relevant to the development of vaginal and rectal microbicides. In particular, recent advances pertaining inherently active microbicide nanosystems and microbicide drug nanocarriers are discussed.

Poly(ethylene glycol) (PEG)-lactic acid nanocarrier-based degradable hydrogels for restoring the vaginal microenvironment

Women with bacterial vaginosis (BV) display reduced vaginal acidity, which make them susceptible to associated infections such as HIV. In the current study, poly(ethylene glycol) (PEG) nanocarrier-based degradable hydrogels were developed for the controlled release of lactic acid in the vagina of BV-infected women. PEG-lactic acid (PEG-LA) nanocarriers were prepared by covalently attaching lactic acid to 8-arm PEG-SH via cleavable thioester bonds. PEG-LA nanocarriers with 4 copies of lactic acid per molecule provided controlled release of lactic acid with a maximum release of 23% and 47% bound lactic acid in phosphate buffered saline (PBS, pH7.4) and acetate buffer (AB, pH4.3), respectively. The PEG nanocarrier-based hydrogels were formed by cross-linking the PEG-LA nanocarriers with 4-arm PEG-NHS via degradable thioester bonds. The nanocarrier-based hydrogels formed within 20 min under ambient conditions and exhibited an elastic modulus that was 100-fold higher than the viscous modulus. The nanocarrier-based degradable hydrogels provided controlled release of lactic acid for several hours; however, a maximum release of only 10%-14% bound lactic acid was observed possibly due to steric hindrance of the polymer chains in the cross-linked hydrogel. In contrast, hydrogels with passively entrapped lactic acid showed burst release with complete release within 30 min. Lactic acid showed antimicrobial activity against the primary BV pathogen Gardnerella vaginalis with a minimum inhibitory concentration (MIC) of 3.6 mg/ml. In addition, the hydrogels with passively entrapped lactic acid showed retained antimicrobial activity with complete inhibition G. vaginalis growth within 48 h. The results of the current study collectively demonstrate the potential of PEG nanocarrier-based hydrogels for vaginal administration of lactic acid for preventing and treating BV.

Novel intravaginal nanomedicine for the targeted delivery of saquinavir to CD4+ immune cells

The goal of this study was to develop and characterize an intravaginal nanomedicine for the active targeted delivery of saquinavir (SQV) to CD4(+) immune cells as a potential strategy to prevent or reduce HIV infection. The nanomedicine was formulated into a vaginal gel to provide ease in self-administration and to enhance retention within the vaginal tract. SQV-encapsulated nanoparticles (SQV-NPs) were prepared from poly(lactic-co-glycolic acid) (PLGA) and conjugated to antihuman anti-CD4 antibody. Antibody-conjugated SQV-NPs (Ab-SQV-NPs) had an encapsulation efficiency (EE%) of 74.4% + 3.7% and an antibody conjugation efficiency (ACE%) of 80.95% + 1.10%. Over 50% of total loaded SQV was released from NPs over 3 days. NPs were rapidly taken up by Sup-T1 cells, with more than a twofold increase in the intracellular levels of SQV when delivered by Ab-SQV-NPs in comparison to controls 1 hour post-treatment. No cytotoxicity was observed when vaginal epithelial cells were treated for 24 hours with drug-free Ab-NPs (1,000 μg/mL), 1% HEC placebo gel (200 mg/mL), or 1% HEC gel loaded with drug-free Ab-NPs (5 mg NPs/g gel, 200 mg/mL of gel mixture). Overall, we described an intravaginal nanomedicine that is nontoxic and can specifically deliver SQV into CD4(+) immune cells. This platform may demonstrate potential utility in its application as postexposure prophylaxis for the treatment or reduction of HIV infection, but further studies are required.

Enhanced bioactivity of internally functionalized cationic dendrimers with PEG cores

Hybrid dendritic-linear block copolymers based on a 4-arm poly(ethylene glycol) (PEG) core were synthesized using an accelerated AB2/CD2 dendritic growth approach through orthogonal amine/epoxy and thiol-yne chemistries. The biological activity of these 4-arm and the corresponding 2-arm hybrid dendrimers revealed an enhanced, dendritic effect with an exponential increase in cell internalization concomitant with increasing amine end groups and low cytotoxicity. Furthermore, the ability of these hybrid dendrimers to induce endosomal escape combined with their facile and efficient synthesis makes them attractive platforms for gene transfection. The 4-arm-based dendrimer showed significantly improved DNA binding and gene transfection capabilities in comparison with the 2-arm derivative. These results combined with the MD simulation indicate a significant effect of both the topology of the PEG core and the multivalency of these hybrid macromolecules on their DNA binding and delivery capablities.

Dendrimer-enabled modulation of gene expression in Chlamydia trachomatis

The obligate intracellular bacterium Chlamydia trachomatis is an important human pathogen. The genome of this organism is small but encodes many genes of currently unknown function that are thought to be involved in virulence. Lack of a system for genetic manipulation has been a key challenge to advancing the understanding of molecular genetics underlying virulence for this bacterium. We developed a dendrimer-enabled system for transformation of C. trachomatis, and used it to demonstrate the efficient and highly specific knockdown of transcript levels from targeted genes. Antisense, sense, and other control oligonucleotides targeting two sets of duplicated genes on the chlamydial chromosome were designed, commercially synthesized, and complexed with generation-4 polyamidoamine (PAMAM) dendrimers. The complexes were given to HEp-2 cell cultures infected for 16 h with C. trachomatis serovar K and then removed three hours later. Infected cultures were harvested 6 h after pulsing, and DNA and RNA/cDNA were prepared for assessment of transcript levels compared to those for the same genes in infected cultures, without dendrimer complexation. In all cases, the targeted gene complexed to dendrimer, but not its duplicate, showed up to 90% transcript attenuation. The duration of attenuation can be extended by repeated pulsing, and in some cases transcript levels from multiple genes can be attenuated in the same organism. This system will allow study of chlamydial gene function in pathogenesis, leading to more effective therapies to treat Chlamydia-induced diseases in a targeted manner.

Poly(amidoamine) dendrimers increase antifungal activity of clotrimazole

Clotrimazole (CLO) is a local imidazolic antifungal agent. A major problem associated with the successful formulation of effective dosage forms containing CLO is its poor aqueous solubility, which presents a hindrance for the local availability of CLO and limits the effective antifungal therapy. In the present study, the effects of various concentrations of poly(amidoamine) (PAMAM) dendrimers generation 2 (G2) and generation 3 (G3) with amine (PAMAM-NH(2)) or hydroxyl surface groups (PAMAM-OH) on aqueous solubility and antifungal activity of CLO were studied. The obtained results showed that all tested PAMAM dendrimers improved the solubility of CLO and the more potent were PAMAM-NH(2) dendrimers. The increase in solubility of CLO was highest at dendrimer concentration of 10 mg/ml. Microbiology studies indicated that only PAMAM-NH(2) dendrimers significantly increased the antifungal activity of CLO (a 4-32-fold increase in the antifungal activity compared to pure CLO) and the most potent was dendrimer PAMAM-NH(2) G2. These observations indicate that PAMAM dendrimers might be considered as potential carriers of CLO and provide further impetus to evaluate these polymers for use in basic drug delivery studies and to design semisolid dosage forms based on dendrimers with antimicrobial drugs, like CLO.

Injectable PAMAM dendrimer-PEG hydrogels for the treatment of genital infections: formulation and in vitro and in vivo evaluation

Local intravaginal drug therapy is preferred for treatment of ascending genital infections during pregnancy. In the present study, an in situ forming biodegradable hydrogel for sustained release of amoxicillin in the cervicovaginal region is described. A generation 4 poly(amidoamine) [G4-(NH(2))(64)] dendrimer with peripheral thiopyridyl terminations is cross-linked with 8-arm polyethylene glycol (PEG) bearing thiol terminations. The hydrogels were formulated and tested in vivo in a pregnant guinea pig model for volume, retention times, biodegradation, tolerability and transport across fetal membrane. The physicochemical characterization of the hydrogels was carried out using differential calorimetry, SEM, and confocal imaging. The hydrogels offer antibacterial activity arising from sustained release of amoxicillin from gels. The in vivo studies in guinea pig showed that 100-200 μL of gel sufficiently covered the cervicovaginal region with a residence time of at least 72 h and gel was primarily retained in the maternal tissues without crossing the fetal membranes into the fetus. The dendrimer gels were stable up to 72 h, and the in vivo biodegradation of gel occurred after 72 h; this correlated well with the in vitro degradation pattern. The pH of the vagina was not altered upon application of the gel, and none of the animals aborted up to 72 h after application of gel. The histological evaluation of the cervical tissues showed absence of edema in the epithelial cell layer, no sloughing of the epithelial or superficial mucous layer, and absence of necrosis and infiltration of inflammatory cells in the submucosal layers, confirming that tissues were tolerant to the gel. The immunohistofluorescence images showed the localization of the gel components on the superficial mucified epithelial layer. The cross-linking density and swelling of hydrogels was impacted by the polymer content, and the 10% hydrogels exhibited the highest cross-link density. The in vitro drug release studies carried out using Franz diffusion cells showed that amoxicillin release from 6 and 10% gels was sustained for 240 h as compared to 3% gels. As the polymer concentration increased to 10%, the release pattern from gels approached diffusion controlled mechanism with diffusional exponent n = 0.49. In conclusion, the biodegradable in situ forming hydrogels of the present study offer a therapeutic option to provide sustained localized delivery of amoxicillin intracervically to the pregnant woman for the treatment of ascending genital infections.

Vaginal delivery of siRNA using a novel PEGylated lipoplex-entrapped alginate scaffold system

Sustained vaginal delivery of siRNA has been precluded by the mucosal barrier lining the vaginal tract. In contrast to prior reports, we showed that conventional lipoplexes administered intravaginally are unable to reach the vaginal epithelium under normal physiological conditions. Here we have developed a novel alginate scaffold system containing muco-inert PEGylated lipoplexes to provide a sustained vaginal presence of lipoplexes in vivo and to facilitate the delivery of siRNA/oligonucleotides into the vaginal epithelium. These PEGylated lipoplex-entrapped alginate scaffolds (PLAS) were fabricated using a freeze-drying method and the entrapment efficiency, release rate, and efficacy were characterized. We demonstrated that the PLAS system had an entrapment efficiency of ~50%, which released PEGylated lipoplexes gradually both in vitro and in vivo. While the presence of alginate diminished the cell uptake efficiency of PEGylated lipoplexes in vitro, as expected, we showed a six-fold increase their uptake into the vaginal epithelium compared to existing transfection systems following intravaginal administration in mice. A significant knockdown of Lamin A/C level was also observed in vaginal tissues using siLamin A/C-containing PLAS system in vivo. Overall, our results indicated the potential of the biodegradable PLAS system for the sustained delivery of siRNA/oligonucleotides to vaginal epithelium.

Inhibition of bacterial growth and intramniotic infection in a guinea pig model of chorioamnionitis using PAMAM dendrimers

Dendrimers have emerged as topical microbicides to treat vaginal infections. This study explores the in vitro, in vivo antimicrobial activity of PAMAM dendrimers, and the associated mechanism. Interestingly, topical cervical application of 500 microg of generation-4 neutral dendrimer (G(4)-PAMAM-OH) showed potential to treat the Escherichia coli induced ascending uterine infection in guinea pig model of chorioamnionitis. Amniotic fluid collected from different gestational sacs of infected guinea pigs posttreatment showed absence of E. coli growth in the cultures plated with it. The cytokine level [tumor necrosis factor (TNFalpha) and interleukin (IL-6 and IL-1beta)] in placenta of the G(4)-PAMAM-OH treated animals were comparable to those in healthy animals while these were notably high in infected animals. Since, antibacterial activity of amine-terminated PAMAM dendrimers is known, the activity of hydroxyl and carboxylic acid terminated PAMAM dendrimers was compared with it. Though the G(4)-PAMAM-NH(2) shows superior antibacterial activity, it was found to be cytotoxic to human cervical epithelial cell line above 10 microg/mL, while the G(4)-PAMAM-OH was non-cytotoxic up to 1mg/mL concentration. Cell integrity, outer (OM) and inner (IM) membrane permeabilization assays showed that G(4)-PAMAM-OH dendrimer efficiently changed the OM permeability, while G(4)-PAMAM-NH(2) and G(3.5)-PAMAM-COOH damaged both OM and IM causing the bacterial lysis. The possible antibacterial mechanism are G(4)-PAMAM-NH(2) acts as polycation binding to the polyanionic lipopolysaccharide in E. coli, the G(4)-PAMAM-OH forms hydrogen bonds with the hydrophilic O-antigens in E. coli membrane and the G(3.5)-PAMAM-COOH acts as a polyanion, chelating the divalent ions in outer cell membrane of E. coli. This is the first study which shows that G(4)-PAMAM-OH dendrimer acts as an antibacterial agent.

Safety, tolerability, and pharmacokinetics of SPL7013 gel (VivaGel): a dose ranging, phase I study

OBJECTIVES

To evaluate safety, tolerability and systemic pharmacokinetics of escalating doses of SPL7013 Gel in healthy women.

DESIGN

: Randomized, double-blind, placebo-controlled dose-escalation trial.

METHODS

Thirty-seven healthy women were randomized to receive 3.5 g of 0.5% (N = 8), 1% (N = 8), or 3% (N = 9) SPL7013 Gel or placebo gel (N = 12), applied vaginally once daily for 7 consecutive days. Genital toxicity was determined by interview, physical examination, assessment of vaginal microflora and colposcopy. Systemic toxicity was determined by nongenital adverse events (AEs) and laboratory assessments. Plasma was collected for pharmacokinetic analysis.

RESULTS

Genital AEs considered potentially product-related were all mild and reported by 5 (20%) women receiving SPL7013 Gel and 2 (17%) women receiving placebo gel. The most common were abdominal pain or discomfort, with no reports of vaginal burning or malodour, or genital-tract pain. There were no clinically significant colposcopic findings, including of genital inflammation or epithelial disruption. Lower concentrations of normal lactobacillary flora occurred during SPL7013 Gel and placebo gel use, with a decrease in anaerobes in the SPL7013 Gel groups. There were no reported cases of bacterial vaginosis, and lactobacilli returned to predose levels in most women after treatment. All nongenital AEs were of mild or moderate severity, expect for a severe tension headache in a woman receiving placebo. There was no absorption of SPL7013 into the systemic circulation.

CONCLUSIONS

SPL7013 Gel applied vaginally once daily for 7 days at concentrations of 0.5% to 3% was safe and well tolerated in healthy, sexually abstinent women, with no evidence of systemic toxicity or absorption.

Transport and biodistribution of dendrimers across human fetal membranes: implications for intravaginal administration of dendrimer-drug conjugates

Dendrimers are emerging as promising topical antimicrobial agents, and as targeted nanoscale drug delivery vehicles. Topical intravaginal antimicrobial agents are prescribed to treat the ascending genital infections in pregnant women. The fetal membranes separate the extra-amniotic space and fetus. The purpose of the study is to determine if the dendrimers can be selectively used for local intravaginal application to pregnant women without crossing the membranes into the fetus. In the present study, the transport and permeability of PAMAM (poly (amidoamine)) dendrimers, across human fetal membrane (using a side by side diffusion chamber), and its biodistribution (using immunofluorescence) are evaluated ex-vivo. Transport across human fetal membranes (from the maternal side) was evaluated using Fluorescein (FITC), an established transplacental marker (positive control, size approximately 400 Da) and fluorophore-tagged G(4)-PAMAM dendrimers (approximately 16 kDa). The fluorophore-tagged G(4)-PAMAM dendrimers were synthesized and characterized using (1)H NMR, MALDI TOF MS and HPLC analysis. Transfer was measured across the intact fetal membrane (chorioamnion), and the separated chorion and amnion layers. Over a 5 h period, the dendrimer transport across all the three membranes was less than <3%, whereas the transport of FITC was relatively fast with as much as 49% transport across the amnion. The permeability of FITC (7.9 x 10(-7) cm(2)/s) through the chorioamnion was 7-fold higher than that of the dendrimer (5.8 x 10(-8) cm(2)/s). The biodistribution showed that the dendrimers were largely present in interstitial spaces in the decidual stromal cells and the chorionic trophoblast cells (in 2.5-4 h) and surprisingly, to a smaller extent internalized in nuclei of trophoblast cells and nuclei and cytoplasm of stromal cells. Passive diffusion and paracellular transport appear to be the major route for dendrimer transport. The overall findings further suggest that entry of drugs conjugated to dendrimers would be restricted across the human fetal membranes when administered topically by intravaginal route, suggesting new ways of selectively delivering therapeutics to the mother without affecting the fetus.

Pre-clinical and behavioural toxicity profile of PAMAM dendrimers in mice

A toxicity study of different polyamidoamine (PAMAM) dendrimers in Swiss albino mice was performed with a clinical overview. In the current study, mice were treated with various G4 dendrimers (NH 2 and OH surface groups) at different dosage levels (low, medium and high) via the intraperitoneal route for 15 consecutive days, followed by a 15 day recovery period. The toxicity profile was investigated in mice for their general behaviour, feed intake, body weight, carbohydrate, lipid and protein metabolism, haematological parameters, histopathology and cell viability. No significant differences were observed in feed intake, body weight and organ weight among the various dendrimer-fed groups and control. In general, dendrimers have no significant effect on the carbohydrate and lipid metabolism. However, declined glucose levels in the high-NH 2 dose group indicates the interference of this dosage level with glucose metabolism. Although all the test groups showed activity in the normal range, the high-NH 2 group showed comparatively higher alanine aminotransferase and aspartate aminotransferase activity. Minor, but insignificant ( p > 0.05), differences were observed in the red blood cells, haematocrit value and haemoglobin of the treated group when compared to the control group in a dose-dependent manner, but these recovered during the recovery period. There was no effect on other haematological parameters. Histopathological evaluation of dendrimer-treated groups did not reveal any abnormalities in the low- and medium-dose groups, but at a high dose level, toxicity was observed in the liver and kidney. However, after the recovery period, toxicity in the high dose level was not found. A cell viability study of cationic dendrimers has shown reduced cytotoxicity after the complexation with a guest molecule such as indomethacin. This study showed that dendrimers are not toxic, in general. The high dose of G4-NH 2 displayed some toxicity; however, that too was recovered after some time.