Comparative in vitro spermicidal activity of chelating agents and synergistic effect with nonoxynol-9 on human sperm functionality

A Cocktail-Inspired Male Birth Control Strategy with Physical/Chemical Dual Contraceptive Effects and Remote Self-Cleared Properties

Inspired by cocktails, we designed a medium term (2-20 weeks) male contraceptive strategy. Through a sequential injection process of four reagents (calcium alginate hydrogel, PEG-Au nanoparticles (PEG-AuNps), EDTA, and PEG-AuNps), physical clogging of the vas deferens and chemical inhibition of the sperm motility were realized simultaneously. The contraceptive period could be directly preset by adjusting the injection ratio of each reagent. More interesting, the embolism area could be readily dredged through a short-time noninvasive near-infrared irradiation. The present study offered an effective and reversible manner to fill the gap of current medium-term contraceptive strategy. In addition, the proposed in vivo pipeline plugging technology, with a flexible noninvasive self-cleared characteristic, might also provide a convenient and reliable strategy for some other biomedical engineering researches.

Potential Use of Antimicrobial Peptides as Vaginal Spermicides/Microbicides

The concurrent increases in global population and sexually transmitted infection (STI) demand a search for agents with dual spermicidal and microbicidal properties for topical vaginal application. Previous attempts to develop the surfactant spermicide, nonoxynol-9 (N-9), into a vaginal microbicide were unsuccessful largely due to its inefficiency to kill microbes. Furthermore, N-9 causes damage to the vaginal epithelium, thus accelerating microbes to enter the women's body. For this reason, antimicrobial peptides (AMPs), naturally secreted by all forms of life as part of innate immunity, deserve evaluation for their potential spermicidal effects. To date, twelve spermicidal AMPs have been described including LL-37, magainin 2 and nisin A. Human cathelicidin LL-37 is the most promising spermicidal AMP to be further developed for vaginal use for the following reasons. First, it is a human AMP naturally produced in the vagina after intercourse. Second, LL-37 exerts microbicidal effects to numerous microbes including those that cause STI. Third, its cytotoxicity is selective to sperm and not to the female reproductive tract. Furthermore, the spermicidal effects of LL-37 have been demonstrated in vivo in mice. Therefore, the availability of LL-37 as a vaginal spermicide/microbicide will empower women for self-protection against unwanted pregnancies and STI.

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

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

Spermicidal activity of dermaseptins

OBJECTIVE

The present study was undertaken to elucidate the spermicidal efficacy of two synthetic antimicrobial peptides, dermaseptin (DS1 and DS4).

METHODS

Twenty samples of fresh semen were obtained from patients aged between 23 and 35 years. The ability of DS to kill sperm was evaluated by the Sander-Cramer test under in vitro conditions.

RESULTS

The data showed that sperm motility was inhibited with various concentrations of DS at different intervals ranging from 2 to 240 min. The effective 100% inhibitory concentration (EC(100)) of DS4 in 2 min during the sperm immobilization assay was 100 microg/mL whereas the sperm immobilization of EC(100) of DS1 was 200 microg/mL. The presence of 0.1% chelating agent ethylenediaminetetraacetic acid (EDTA) reduced the EC(100) of DS4 to 10 microg/mL whereas less than a two-time enhancement in DS1 activity was observed upon combination with EDTA. The action of DSs on sperm motility was observed to be dose dependent. Supplementation with pentoxifylline and that with calcium are known to enhance the motility of sperm but they did not prevent the spermicidal action of DSs.

CONCLUSION

This present study indicates that DS is an effective agent to kill sperm. In view of this fact, it is suggested that DS4 has antibacterial, antiviral, antifungal and potentially spermicidal activities and could be a potent vaginal contraceptive.

The vagina as a route for systemic drug delivery

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

EDTA-induced activation of Ca-regulated proteins in the vaginal mucosa

The effects of EDTA on the expression and topologic localization of mitogen-activated protein (MAP) kinases (ERK, JNK, and p38), along with nitric oxide synthase (NOS), I-KappaB, and p53 were examined to elucidate the host response provoked by the intravaginal application of a female controlled drug delivery system (FcDDS) containing a spermicidal/microbicidal agent and EDTA. Immunohistochemical and immunoblotting studies were conducted to identify and quantitate the EDTA-inducible proteins in vaginal mucosa. The content of nitrite, which is one of the primary stable breakdown products of nitric oxide (NO), was determined to correlate the expression of NOS with NO formation in HeLa cervical carcinoma cell line. The immunohistochemical study demonstrated that the modulation of the calcium gradient by EDTA activated MAP kinases (ERK and JNK) in the rabbit vaginal mucosa. The results of Western immunoblot study demonstrated differential expression of MAP kinases (ERK and JNK) with EDTA treatment, whereas the expression of NOS and NF-KappaB was not affected by EDTA. There was no significant difference in nitrite production in the HeLa cell line upon exposure to EDTA compared with the control, which was consistent with the results of the Western blot study. The results of this work support that the regulation of MAP kinase was affected by calcium, which is controlled by chelation activity of EDTA. The specific tissue responses exerted by the loading components of a biomaterial-based system should be fully taken into consideration for its intravaginal application.

Characterization of a female controlled drug delivery system for microbicides

In this study, the feasibility of a carbopol 934P-HPMC-based gel formulation as a vaginal drug delivery system was evaluated. A vaginal fluid simulant (VFS) was utilized to simulate human vaginal mucus. The viscosity of the carbopol-HPMC gel system and VFS was examined using a cone and plate viscometer. The surface tension of VFS was measured using a capillary rising method. Differential scanning calorimetry (DSC) was employed to investigate the effect of carbopol gel on the conformational changes of rat vaginal membrane. The viscosity of carbopol gel increased as the pH of the system increased from 4.0 to 6.0. The viscosity of HPMC gel remained the same irrespective of pH of the system. The viscosity of the carbopol gel significantly increased, when HPMC (0.5-1.5%) was added to the system. The optimal viscosity value (1.5-2.0 poises) was achieved at 1.0-1.5% carbopol (pH 4.0) with the presence of 1.0-1.5% HPMC. There were mucin concentration dependent changes in viscosity and surface tension of VFS. The results of DSC analysis of rat vaginal membrane showed that the profiles of thermal stability for both carbopol-treated and the untreated control at the temperature ranging from 40 to 90 degrees C were almost identical. The thermal denaturation temperatures (Td) of the carbopol-treated membrane and the untreated control were not significantly different from each other. The combination of carbopol and HPMC seems to be an ideal formulation as a vaginal delivery system. Mucin played an important role in the regulation of viscosity and surface tension of VFS. DSC study demonstrated that carbopol gel showed good biocompatibility and did not cause any conformational changes in rat vaginal membrane.

Effects of chelating agents on the rheological property of cervical mucus

As an ongoing effort to elucidate the mechanisms involved in the calcium-dependent fertility regulation process, the viscoelastic properties of the mucus obtained from lamb cervix and human semen, as well as their water and total protein contents after exposure to EDTA, a chelating agent, or Nonoxynol-9 (N-9), a spermicidal agent, were examined. The viscosity was measured using a Cone Plate Digital Viscometer, while the water and total protein contents were determined by the lyophilization process and the Lowry method, respectively. The significant changes in the rheological properties of mucus, such as its viscosity and the water content, upon exposure to EDTA were demonstrated. The viscosity of cervical mucus and human semen were significantly increased by EDTA treatment (as compared to the controls): lamb cervical mucus (2.9 +/- 0.3 vs. 2.2 +/- 0.3 cps) and human semen (5.0 +/- 0.3 vs. 4.3 +/- 0.3 cps), respectively. The hydration rate was decreased by EDTA treatment as compared with the control (93.6 +/- 0.7 vs. 96.8 +/- 0.8%). Among tested samples, the reduction in the percentage of sperm penetration through the cervical mucus was the highest in the mucus containing EDTA, which had the lowest water content (93.6 +/- 0.7%), indicating that there is a positive relationship between the hydration rate of the cervical mucus and its ability to permit the penetration of spermatozoa. This result indicates that spermicidal activity exerted by high concentrations of EDTA is in part due to its effect on the rheological properties of cervical mucus or semen.

Dose-response effects of gramicidin-D, EDTA, and nonoxynol-9 on sperm motion parameters and acrosome status

Previous reports showed that gramicidin-D (G-D), a polypeptide with antiviral and antimicrobial properties, nonoxynol-9 (N9), a common spermicidal detergent, and EDTA, a Ca-Mg chelating agent, inhibited sperm motility and cervical mucus penetration. The purpose of this study was to determine the dose-response effects of G-D, N9, EDTA and G-D + EDTA on sperm motion parameters and acrosome status. Semen specimens from known fertile donors were subjected to computer-assisted semen analysis of motility, path velocity, progressive velocity, and hyperactivation prior to and after incubation with varying concentrations of gramicidin-D, EDTA and nonoxynol-9. Each specimen was also prepared for acrosome status using rhodamine isothiocyanate conjugated pisum sativum agglutinin (RITC-PSA). There was a significant decrease in motility by G-D, EDTA, G-D + EDTA, and N9 at all doses as compared to the fresh specimen. N9 completely immobilized all sperm at each dose. Progressive velocity and path velocity also decreased in a dose-response manner. Sperm hyperactive motility also significantly decreased in all groups. The majority of sperm remained acrosome intact following exposure to all doses tested, whereas N9 resulted in complete breakdown/release of the acrosomal contents. This study confirms previous reports that G-D, EDTA, and N9 significantly impair sperm motility and motion parameters. The effective 100% inhibitory concentration was seen only with N9, whereas G-D, EDTA, and G-D + EDTA resulted in incomplete impairment of sperm motion parameters. At the concentrations used, N9 demonstrated potent spermostatic activity. Gramicidin-D and EDTA should be further studied for their potential contraceptive spermostatic activity.

Synergistic effect of gramicidin and EDTA in inhibiting sperm motility and cervical mucus penetration in vitro

Gramicidin, a linear polypeptide with antiviral and antimicrobial properties, was compared in vitro with a commonly used spermicidal detergent-nonoxynol-9 (N9). The inhibition of sperm functions was evaluated by computer-assisted semen analysis (CASA) for sperm motility, in cervical mucus penetration assay, and by colorimetric tetrazolium salt and lactate dehydrogenase release assays routinely employed for testing the toxicity of drugs. The effective 100% inhibitory concentration (IC100) of gramicidin in a 2-min sperm immobilization assay by CASA was equal to 4 micrograms/ml, whereas IC100 of N9 was equal to 200 micrograms/ml. The presence of 0.1% of chelating agent, EDTA, reduced IC100 of gramicidin to 10 ng/ml, while less than a twofold enhancement in N9 activity was observed upon combination with EDTA. Likewise, the gramicidin/EDTA combination was 100,000 times more potent than N9/EDTA in the sperm penetration assay. Quantitative toxicity tests confirmed that gramicidin is a potent spermostatic rather than spermicidal agent. Further development of a gramicidin/EDTA formulation is warranted as a nontoxic topical contraceptive with activity against viral and microbial sexually transmitted diseases (STDs).

Review: in vitro spermicidal tests

This review analyzes in vitro spermicidal tests that have been used to evaluate the spermicidal activity of contraceptive products. Special requirements and processes in numerous technologies were also reviewed. Nonoxynol-9 (N-9) was used as an example of a vaginally delivered spermicidal agent, and its spermicidal potency was compared by various spermicidal tests, such as Sander-Cramer, computer-assisted semen analysis, hypoosmotic swelling test, cervical mucus penetration test, and flow cytometry, and advantages and disadvantages of each test were specified. This provides an insight into the different aspects of sperm functionality on which each spermicidal agent exerts its activity. A rationale of the best combination of in vitro spermicidal tests, with particular emphasis on a simple and efficient strategy that targets the complete fertility control, was explained.

In vitro permeation study of a mucoadhesive drug delivery system for controlled delivery of nonoxynol-9

A carbopol 934P-based drug delivery system (AmDDS) was developed to achieve the dual-controlled delivery of Nonoxynol-9 (N-9), a spermicidal agent, and EDTA, a potentiator of spermicidal activity. This gel-type system made intimate contact with vaginal mucosa and maintained an effective drug concentration within the vagina for a prolonged period of time. An existing mathematical model, based on a unilayer diffusion membrane, was applied for describing permeation of N-9 through vaginal mucosa. Vaginal permeation of N-9 from AmDDS was negligible over the initial 5 hr, then increased in a Q versus t pattern, but remained low. A relationship was observed between the permeation rate (Js) of drug through vaginal mucosa and the release flux (Q/t1/2) from AmDDS, which showed that the permeation rate (Js) increased with increased square of the release flux [(Q/t1/2)2] in a hyperbolic manner. This result indicated that release of N-9 from AmDDS is still the rate-limiting step at doses within the tested range. EDTA, at concentration of up to 0.32%, did not change the permeation rate of N-9 through vaginal mucosa. It is thus concluded that the developed AmDDS can control the intravaginal delivery of N-9 as well as its permeation through vaginal mucosa.