A scanning electron microscopic study of the contraceptive vaginal ring

Medical Applications of Porous Biomaterials: Features of Porosity and Tissue-Specific Implications for Biocompatibility

Porosity is an important material feature commonly employed in implants and tissue scaffolds. The presence of material voids permits the infiltration of cells, mechanical compliance, and outward diffusion of pharmaceutical agents. Various studies have confirmed that porosity indeed promotes favorable tissue responses, including minimal fibrous encapsulation during the foreign body reaction (FBR). However, increased biofilm formation and calcification is also described to arise due to biomaterial porosity. Additionally, the relevance of host responses like the FBR, infection, calcification, and thrombosis are dependent on tissue location and specific tissue microenvironment. In this review, the features of porous materials and the implications of porosity in the context of medical devices is discussed. Common methods to create porous materials are also discussed, as well as the parameters that are used to tune pore features. Responses toward porous biomaterials are also reviewed, including the various stages of the FBR, hemocompatibility, biofilm formation, and calcification. Finally, these host responses are considered in tissue specific locations including the subcutis, bone, cardiovascular system, brain, eye, and female reproductive tract. The effects of porosity across the various tissues of the body is highlighted and the need to consider the tissue context when engineering biomaterials is emphasized.

The Vaginal Microbiota, Bacterial Biofilms and Polymeric Drug-Releasing Vaginal Rings

The diversity and dynamics of the microbial species populating the human vagina are increasingly understood to play a pivotal role in vaginal health. However, our knowledge about the potential interactions between the vaginal microbiota and vaginally administered drug delivery systems is still rather limited. Several drug-releasing vaginal ring products are currently marketed for hormonal contraception and estrogen replacement therapy, and many others are in preclinical and clinical development for these and other clinical indications. As with all implantable polymeric devices, drug-releasing vaginal rings are subject to surface bacterial adherence and biofilm formation, mostly associated with endogenous microorganisms present in the vagina. Despite more than 50 years since the vaginal ring concept was first described, there has been only limited study and reporting around bacterial adherence and biofilm formation on rings. With increasing interest in the vaginal microbiome and vaginal ring technology, this timely review article provides an overview of: (i) the vaginal microbiota, (ii) biofilm formation in the human vagina and its potential role in vaginal dysbiosis, (iii) mechanistic aspects of biofilm formation on polymeric surfaces, (iv) polymeric materials used in the manufacture of vaginal rings, (v) surface morphology characteristics of rings, (vi) biomass accumulation and biofilm formation on vaginal rings, and (vii) regulatory considerations.

Bacterial biofilm formation on vaginal ring pessaries used for pelvic organ prolapse

INTRODUCTION AND HYPOTHESIS

The objective of this study was to characterize the bacterial biofilm on vaginal ring pessaries used to treat pelvic organ prolapse and investigate the relationship between biofilm phenotype and patient symptoms and clinical signs that are suggestive of inflammation.

METHODS

This was a cross-sectional observational study of 40 women wearing a ring-shaped pessary continuously for at least 12 weeks. Participants underwent a clinical examination, and the pessary was removed. Clinical signs were recorded. A swab from the pessary surface and a high vaginal swab were collected from each woman. Participants completed a questionnaire on symptoms. Pessary biofilm presence and phenotype were determined by scanning electron microscopy (SEM). Vaginal and pessary bacterial composition was determined by 16S rRNA gene sequencing. The relationship between biofilm phenotype and symptoms and clinical signs was assessed using logistic regression.

RESULTS

SEM confirmed biofilm formation on all 40 pessaries. Microbiota data were available for 25 pessary swabs. The pessary biofilm microbiota was composed of bacteria typically found in the vagina and was categorized into Lactobacillus-dominated (n = 10/25 pessaries, 40%) communities and Lactobacillus-deficient communities with high relative abundance of anaerobic/facultative anaerobes (n = 15/25 pessaries, 60%). While increasing age was associated with presence of a Lactobacillus-deficient pessary biofilm (odds ratio = 3.60, 95% CI [1.16-11.22], p = 0.04), no associations between biofilm microbiota composition and symptoms or clinical signs were observed.

CONCLUSIONS

Lactobacillus-deficient biofilms commonly form on pessaries following long-term use. However, the contribution of biofilm phenotype to symptoms and clinical signs remains to be determined.

Surface roughness of different contraceptive vaginal rings: evaluation by scanning electron microscope (SEM)

Objective: The aim of the study was to evaluate whether the compositions of the ethylene vinyl acetate (EVA) membrane of two different contraceptive vaginal rings could influence the surface roughness, which is associated with the possible accumulation of vaginal biomass on the rings during use.Methods: We measured and compared the surface roughness of unused vaginal rings, NuvaRing and Ornibel, using a scanning electron microscope (SEM) and dedicated software that can convert SEM images into 3D models. Average roughness (Ra), average quadratic roughness (Rq) and mean height of the irregularities at 10 points (Rz) were calculated.Results: Different thicknesses of the EVA membranes between the two rings were noted. No significant differences were found between the two rings in the three evaluated values of surface roughness (NuvaRing vs Ornibel, respectively: Ra, 1.53 ± 0.14 vs 1.61 ± 0.14 µm, p = 0.141; Rq, 2.03 ± 0.25 vs 2.07 ± 0.16 µm, p = 0.688; Rz, 11.4 ± 3.1 vs 11.4 ± 2.4 µm, p = 0.987).Conclusion: The different composition of the vaginal rings' EVA membrane is not associated with different surface roughness. Ornibel is equivalent to NuvaRing in terms of surface roughness, despite the different composition of the membrane polymers.

Contraceptive rings promote vaginal lactobacilli in a high bacterial vaginosis prevalence population: A randomised, open-label longitudinal study in Rwandan women

Background

Hormonal contraception has been associated with a reduced risk of vaginal dysbiosis, which in turn has been associated with reduced prevalence of sexually transmitted infections (STIs), including HIV. Vaginal rings are used or developed as delivery systems for contraceptive hormones and antimicrobial drugs for STI and HIV prevention or treatment. We hypothesized that a contraceptive vaginal ring (CVR) containing oestrogen enhances a lactobacilli-dominated vaginal microbial community despite biomass accumulation on the CVR’s surface.

Methods

We enrolled 120 women for 12 weeks in an open-label NuvaRing^® study at Rinda Ubuzima, Kigali, Rwanda. Vaginal and ring microbiota were assessed at baseline and each ring removal visit by Gram stain Nugent scoring (vaginal only), quantitative PCR for Lactobacillus species, Gardnerella vaginalis and Atopobium vaginae, and fluorescent in situ hybridization to visualize cell-adherent bacteria. Ring biomass was measured by crystal violet staining.

Results

Bacterial vaginosis (BV) prevalence was 48% at baseline. The mean Nugent score decreased significantly with ring use. The presence and mean log₁₀ concentrations of Lactobacillus species in vaginal secretions increased significantly whereas those of G. vaginalis and presence of A. vaginae decreased significantly. Biomass accumulated on the CVRs with a species composition mirroring the vaginal microbiota. This ring biomass composition and optical density after crystal violet staining did not change significantly over time.

Conclusions

NuvaRing^® promoted lactobacilli-dominated vaginal microbial communities in a population with high baseline BV prevalence despite the fact that biomass accumulated on the rings.

Association of vaginal dysbiosis and biofilm with contraceptive vaginal ring biomass in African women

We investigated the presence, density and bacterial composition of contraceptive vaginal ring biomass and its association with the vaginal microbiome. Of 415 rings worn by 120 Rwandese women for three weeks, the biomass density was assessed with crystal violet and the bacterial composition of biomass eluates was assessed with quantitative polymerase chain reaction (qPCR). The biomass was visualised after fluorescence in situ hybridisation (FISH) and with scanning electron microscopy (SEM). The vaginal microbiome was assessed with Nugent scoring and vaginal biofilm was visualised after FISH. All vaginal rings were covered with biomass (mean optical density (OD) of 3.36; standard deviation (SD) 0.64). Lactobacilli were present on 93% of the rings, Gardnerella vaginalis on 57%, and Atopobium vaginae on 37%. The ring biomass density was associated with the concentration of A. vaginae (OD +0.03; 95% confidence interval (CI) 0.01–0.05 for one log increase; p = 0.002) and of G. vaginalis (OD +0.03; (95% CI 0.01–0.05; p = 0.013). The density also correlated with Nugent score: rings worn by women with a BV Nugent score (mean OD +0.26), and intermediate score (mean OD +0.09) had a denser biomass compared to rings worn by participants with a normal score (p = 0.002). Furthermore, presence of vaginal biofilm containing G. vaginalis (p = 0.001) and A. vaginae (p = 0.005) correlated with a denser ring biomass (mean OD +0.24 and +0.22 respectively). With SEM we observed either a loose network of elongated bacteria or a dense biofilm. We found a correlation between vaginal dysbiosis and the density and composition of the ring biomass, and further research is needed to determine if these relationships are causal. As multipurpose vaginal rings to prevent pregnancy, HIV, and other sexually transmitted diseases are being developed, the potential impact of ring biomass on the vaginal microbiota and the release of active pharmaceutical ingredients should be researched in depth.

Bacterial biofilms in the vagina

A bacterial biofilm is a structured community of bacteria in a self-produced extracellular matrix, adherent to an inert surface or biological tissue. The involvement of biofilm in a bacterial infection implies that the infection is difficult to treat and that the patient will probably experience relapses of the condition. In bacterial vaginosis (BV), the lactobacilli concentration decreases, while the bacterial load of other (facultative) anaerobic bacteria increases. A hallmark of BV is the presence of clue cells, now known as the result of a polymicrobial biofilm formed in vaginal epithelial cells. Current knowledge of the individual roles of bacterial species involved in polymicrobial BV biofilms or interactions between these species are not fully known. In addition, knowledge of the composition matrix and triggers of biofilm formation is still lacking. Bacteria are able to attach to the surface of indwelling medical devices and cover these surfaces with biofilm. Vaginally inserted devices, such as tampons, intra-uterine devices and vaginal rings, can also be colonized by bacteria and be subjected to biofilm formation. This might hamper release of active product in case of drug-releasing devices such as vaginal rings, or promote the presence of unfavorable bacteria in the vagina. This paper reviews current knowledge of biofilms in the vaginal environment.

Effects of a One Year Reusable Contraceptive Vaginal Ring on Vaginal Microflora and the Risk of Vaginal Infection: An Open-Label Prospective Evaluation

BACKGROUND

A contraceptive vaginal ring (CVR) containing Nestorone® (NES) and ethinyl estradiol (EE) that is reusable for 1- year (13 cycles) is under development. This study assessed effects of this investigational CVR on the incidence of vaginal infections and change in vaginal microflora.

METHODS

There were 120 women enrolled into a NES/EE CVR Phase III trial and a microbiology sub-study for up to 1- year of cyclic product use. Gynecological examinations were conducted at baseline, the first week of cycle 6 and last week of cycle 13 (or during early discontinuation visits). Vaginal swabs were obtained for wet mount microscopy, Gram stain and culture. The CVR was removed from the vagina at the last study visit and cultured. Semi-quantitative cultures for Lactobacillus, Gardnerella vaginalis, Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, anaerobic gram negative rods (GNRs), Candida albicans and other yeasts were performed on vaginal and CVR samples. Vaginal infections were documented throughout the study.

RESULTS

Over 1- year of use, 3.3% of subjects were clinically diagnosed with bacterial vaginosis, 15.0% with vulvovaginal candidiasis, and 0.8% with trichomoniasis. The detection rate of these three infections did not change significantly from baseline to either Cycle 6 or 13. Nugent scores remained stable. H2O2-positive Lactobacillus dominated vaginal flora with a non-significant prevalence increase from 76.7% at baseline to 82.7% at cycle 6 and 90.2% at cycle 13, and a median concentration of 107 colony forming units (cfu) per gram. Although anaerobic GNRs prevalence increased significantly, the median concentration decreased slightly (104 to 103cfu per gram). There were no significant changes in frequency or concentrations of other pathogens. High levels of agreement between vaginal and ring surface microbiota were observed.

CONCLUSION

Sustained use of the NES/EE CVR did not increase the risk of vaginal infection and was not disruptive to the vaginal ecosystem.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00263341, NCT00455156.

Intravaginal rings as delivery systems for microbicides and multipurpose prevention technologies

There is a renewed interest in delivering pharmaceutical products via intravaginal rings (IVRs). IVRs are flexible torus-shaped drug delivery systems that can be easily inserted and removed by the woman and that provide both sustained and controlled drug release, lasting for several weeks to several months. In terms of women's health care products, it has been established that IVRs effectively deliver contraceptive steroids and steroids for the treatment of postmenopausal vaginal atrophy. A novel application for IVRs is the delivery of antiretroviral drugs for the prevention of human immunodeficiency virus (HIV) genital infection. Microbicides are antiviral drugs delivered topically for HIV prevention. Recent reviews of microbicide IVRs have focused on technologies in development and optimizing ring design. IVRs have several advantages, including the ability to deliver sustained drug doses for long periods of time while bypassing first pass metabolism in the gut. IVRs are discreet, woman-controlled, and do not require a trained provider for placement or fitting. Previous data support that women and their male sexual partners find IVRs highly acceptable. Multipurpose prevention technology (MPT) products provide protection against unintended/mistimed pregnancy and reproductive tract infections, including HIV. Several MPT IVRs are currently in development. Early clinical testing of new microbicide and MPT IVRs will require a focus on safety, pharmacokinetics and pharmacodynamics. Specifically, IVRs will have to deliver tissue concentrations of drugs that are pharmacodynamically active, do not cause mucosal alterations or inflammation, and do not change the resident microbiota. The emergence of resistance to antiretrovirals will need to be investigated. IVRs should not disrupt intercourse or have high rates of expulsion. Herein, we reviewed the microbicide and MPT IVRs currently in development, with a focus on the clinical aspects of IVR assessment and the challenges facing microbicide and MPT IVR product development, clinical testing, and implementation. The information in this review was drawn from PubMed searches and a recent microbicide/MPT product development workshop organized by CONRAD.

Vaginal health in contraceptive vaginal ring users - A review

BACKGROUND

To provide an overview of the available data from clinical studies of vaginal conditions in women who use a vaginal ring as a contraceptive.

METHODS

A systematic review of the literature.

RESULTS

Millions of women have already used the ethylene vinyl acetate vaginal ring that releases ethinylestradiol and etonogestrel for contraception. Because of its small size, more than four out of five women using the ring report that they do not feel it, even during sexual intercourse. No colposcopic or cytological changes have been observed in users, although approximately 10% have increased vaginal discharge. While in vitro studies have shown adhesion of Candida yeasts to the vaginal ring surface, clinical studies have not demonstrated a greater incidence of Candida infections compared to users of equivalent oral contraceptives. Some clinical studies suggest a lower incidence of bacterial vaginosis. No interaction exists between concomitant use of the vaginal ring and other drugs or products for vaginal use.

CONCLUSION

The use of a contraceptive vaginal ring does not alter the vaginal ecosystem and therefore does not substantially affect vaginal health.

Safe and sustained vaginal delivery of pyrimidinedione HIV-1 inhibitors from polyurethane intravaginal rings

The potent antiretroviral pyrimidinediones IQP-0528 (PYD1) and IQP-0532 (PYD2) were formulated in polyurethane intravaginal rings (IVRs) as prophylactic drug delivery systems to prevent the sexual transmission of HIV-1. To aid in the selection of a pyrimidinedione candidate and the optimal loading of the drug in the IVR delivery system, four pyrimidinedione IVR formulations (PYD1 at 0.5 wt% [PYD1(0.5 wt%)], PYD1(1 wt%), PYD2(4 wt%), and PYD2(14 wt%)) were evaluated in pigtail macaques over 28 days for safety and pyrimidinedione vaginal biodistribution. Kinetic analysis of vaginal proinflammatory cytokines, native microflora, and drug levels suggested that all formulations were safe, but only the high-loaded PYD2(14 wt%) IVR demonstrated consistently high pyrimidinedione vaginal fluid and tissue levels over the 28-day study. This formulation delivered drug in excess of 10 μg/ml to vaginal fluid and 1 μg/g to vaginal tissue, a level over 1,000 times the in vitro 50% effective concentration. The in vitro release of PYD1 and PYD2 under nonsink conditions correlated well with in vivo release, both in amount and in kinetic profile, and therefore may serve as a more biologically relevant means of evaluating release in vitro than typically employed sink conditions. Lastly, the pyrimidinediones in the IVR formulation were chemically stable after 90 days of storage at elevated temperature, and the potent nanomolar-level antiviral activity of both molecules was retained after in vitro release. Altogether, these results point to the successful IVR formulation and vaginal biodistribution of the pyrimidinediones and demonstrate the usefulness of the pigtail macaque model in evaluating and screening antiretroviral IVR formulations prior to preclinical and clinical evaluation.

Microbial biofilms on the surface of intravaginal rings worn in non-human primates

Millions of intravaginal rings (IVRs) are used by women worldwide for contraception and for the treatment of vaginal atrophy. These devices also are suitable for local and systemic sustained release drug delivery, notably for antiviral agents in human immunodeficiency virus pre-exposure prophylaxis. Despite the widespread use of IVRs, no studies have examined whether surface-attached bacterial biofilms develop in vivo, an important consideration when determining the safety of these devices. The present study used scanning electron microscopy, fluorescence in situ hybridization and confocal laser scanning microscopy to study biofilms that formed on the surface of IVRs worn for 28 days by six female pig-tailed macaques, an excellent model organism for the human vaginal microbiome. Four of the IVRs released the nucleotide analogue reverse transcriptase inhibitor tenofovir at a controlled rate and the remaining two were unmedicated. Large areas of the ring surfaces were covered with monolayers of epithelial cells. Two bacterial biofilm phenotypes were found to develop on these monolayers and both had a broad diversity of bacterial cells closely associated with the extracellular material. Phenotype I, the more common of the two, consisted of tightly packed bacterial mats approximately 5 µm in thickness. Phenotype II was much thicker, typically 40 µm, and had an open architecture containing interwoven networks of uniform fibres. There was no significant difference in biofilm thickness and appearance between medicated and unmedicated IVRs. These preliminary results suggest that bacterial biofilms could be common on intravaginal devices worn for extended periods of time.