Background:  To address the issue of systemic delivery of anti-HIV drugs such as their insoluble nature and short half-life, we are investigating biodegradable nanoparticles as a delivery vehicle for these drugs.

Methods:  In this study, nanoparticles of ~100 nm in diameter were loaded with 16.6 % w/w ritonavir. This formulation was evaluated for inhibition of HIV-1_ADA replication in monocyte-derived macrophages (MDM). MDM were cultured for 7 days and infected with HIV-1_ADA. Control uninfected cells were maintained as controls. After 72 h post-infection cells were treated with control nanoparticles, ritonavir-loaded nanoparticles (RNP) or equivalent concentrations of ritonavir. Uninfected and HIV-1-infected cells were treated with both control and RNP to evaluate the effects of incubation of MDM with nanoparticles and study the inhibition of HIV-1-infection. Supernatant samples were collected and RT activity was measured to determine level of productive replication. Three concentrations of control nanoparticles (0.5, 5.0, 50 µg/mL equivalent to 0.1, 1, 10 µM drug, respectively) were used. Ritonavir alone was used at 1 and 10 µM since (equivalent to 5.0 and 50 µg/mL of nanoparticle formulations).

Results:  Nanoparticles demonstrated sustained release of the encapsulated drug with about 80% of the cumulative drug release in 10 days. Drug alone at 10 µM and RNP at 50 µg/mL (10 µM drug) led to significant reduction in RT activity in culture supernatants within 1 week (p <0.001) as compared to HIV-1_ADA and 50 µg/mL CNP. Each condition was analyzed in triplicates and MTT activity was determined to assay changes in metabolic activity due to treatments. Only high concentrations of ritonavir-alone demonstrated toxicity in the form of reduced MTT activity and abnormal morphology. No toxicity was observed with RNP or control nanoparticles. Replicate wells from the same experiment were fixed and immunostained with CD68 (a macrophage marker) to visualize changes in morphology due to nanoparticles treatment and rescue of cells from cytophathic effects. Nanoparticles were also shown biocompatible with human neurons up to 1 mg/mL concentration. 

Conclusions:  The results of our studies thus demonstrate that nanoparticles can be used as a delivery vehicle for anti-HIV drugs. Our future goal is to modify drug-loaded nanoparticles with a TAT peptide to study the transport and central nervous system delivery of anti-HIV drugs.