Measurement and modulation of nonoxynol-9 diffusion and bioactivity against spermatozoa in human cervical mucus

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.

Factors influencing nonoxynol-9 permeation and bioactivity in cervical mucus

The effects of delivery gel pH and osmolarity on both the mass transport and 'biodiffusion' of the spermicide nonoxynol-9 (N9) in bovine cervical mucus were evaluated. Delivery gels were calcium chloride crosslinked alginate containing 3% N9, and were manufactured over a pH range of 3.4 to 5.9 and an osmolarity range of 300 to 900 mosmol. Mass transfer parameters (diffusion coefficients and total drug loading) were determined using a new UV spectrophotometric technique while biodiffusion (the diffusion distance into mucus at which sperm are killed) was assessed using the Double Ended Test. It was found that delivery gel pH had a significant effect on spermicidal efficacy of the alginate-N9 system; biodiffusion increased with decreasing pH. Actual N9 diffusion into mucus was found to be influenced by both the delivery gel pH and osmolarity. At high N9 concentration (near the gel/mucus interface), mass transport tended to decrease with decreasing pH at the highest osmolarity. At low concentration, mass transport tended to decrease with increasing osmolarity and decrease with increasing pH at the highest osmolarity. The difference between low and high concentration behavior can be attributed to N9 micelle formation. These findings are interpreted in the context of the design of intravaginal drug delivery vehicles for spermicides.

Diffusion of nonoxynol-9 into human semen in vitro

The diffusion of [125I]-nonoxynol-9 into human semen was investigated in vitro before and after liquefaction. No significant difference was found in the distribution of [125I]-nonoxynol-9 within columns of preliquefied semen, liquefied semen, seminal plasma, or water after < or = 120 minutes of diffusion; however, significantly more nonoxynol-9 entered preliquefied semen. The concentration of nonoxynol-9 that entered semen in vitro was greater than its ED100 and the bioavailability was confirmed by demonstration of the retention of spermicidal action. These results indicate that the gel state of preliquefied semen does not inhibit the entry or action of nonoxynol-9 and, consequently, sperm would be exposed to it immediately when it is used in vivo as a vaginal spermicide.

Alteration of human sperm kinematics in cervical mucus due to nonoxynol-9

Traditional endpoints of the double-ended test (DET), a contraceptive screening assay used to evaluate the ability of a compound to permeate cervical mucus and inhibit sperm progression, ignore important information about sublethal effects upon sperm cells. Improved contraceptive agents may capitalize on such sublethal aspects. This study utilized a DET testing protocol that included measurement of human sperm motion characteristics as an indicator of cell function within spermicide-exposed human mucus. The currently available spermicide nonoxynol-9 (N9) was used as the test compound and was dissolved in two different delivery solutions, deionized (DI) water and saline, to evaluate the effects of the osmolarity and pH of the delivery vehicle on test results. The N9-water treatment demonstrated significantly greater activity than the N9-saline treatment in terms of all measured variables, exhibiting an apparent "biopermeation" distance approximately 3 mm further into the mucus. The DI water control treatment displayed less activity than N9-saline in terms of the vanguard penetration distance, but comparable or greater activity in terms of inhibiting kinematic variables. The saline control treatment had no effect in terms of any measured variable. Dose responses to N9 of sperm in mucus were inferred from DET results combined with direct measures of N9 diffusion. These were compared to dose responses to N9 of seminal sperm, indicating that N9 inhibits sperm motion at lower concentrations in mucus than in semen.