Title : Cytotoxicity assessment of combined drug-loaded polymeric nanoparticles for the treatment of HSV-2/HIV-1 co-infection
The associated comorbidity of Herpes Simplex Virus type 2 (HSV-2) with Human Immunodeficiency Virus (HIV-1) infection has become common because of the similar risk factors that the two viruses share. This relationship between the two viruses is responsible for the increase in HIV acquisition and transmission. Currently, there is no fixed dose combination (FDC) drug in use to manage HSV-2 and HIV-1 co-infection, and recent findings have shown that HIV and HSV are becoming resistant to antiretroviral and antiviral therapy. The arrival of nanotechnology has assisted in the reformulation of existing drugs to improve drug delivery and enhance drug efficacy. The current study aimed at improving the treatment options for HSV-2/HIV-1 co-infection and reducing pill burden with the use of nanotechnology. Here, tenofovir disproxil fumarate (TDF) and valacyclovir (VCV) were the antiretroviral and antiviral drugs encapsulated in a polymer (polycaprolactone). Different concentrations of the drugs (1:1, 1:2, 2:1) were encapsulated in polycaprolactone (PCL) at varied drug to polymer ratios (1:1, 1:1.5, 1:2) to form nanoparticles. Double emulsion solvent evaporation method was used to formulate biodegradable polymeric nanoparticles containing both drugs (TDF-VCV-PCL NPs). The formulated nanoparticles were characterized using Malvern zetasizer, scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier transform infra-red spectroscopy (FTIR) to determine the size, polydispersity index, surface charge and the morphology of the formulated nanoparticles. Furthermore, the cytotoxicity profiling of TDF-VCV-PCL NPs were assessed in vitro in Vero cells. Viral inhibition of HSV-2/HIV-1 infected cells treated with the NPs was also determined using the neutralization assay. Characterisation of the combined drug-loaded polymeric nanoparticles showed an average particle size, PDI and ZP of 168.5±1.7 nm, 0.223, -27.3±0.5 mV, respectively. In addition, FTIR analysis showed successful integration of the combined drugs in the polymer, while SEM revealed that the nanoparticles are spherical in shape with smooth surfaces. The cytotoxicity assay of TDF-VCV-PCL NPs in Vero cells showed no significant toxic effect to the cells after 24 hours of treatment. Therefore, the use of biodegradable polycaprolactone to entrap antiretroviral and antiviral drugs may be a better treatment option for HSV-2/HIV-1 co-infection as the nanoparticles containing the combined drugs showed little or no adverse effect on the cells. The efficacy of the nanoparticles to effectively neutralize the viruses showed that this treatment approach may help in developing the first fixed dose combination (FDC) drug that will reduce pill burden with high efficacy against HSV-2/HIV-1 co-infection.