Preparation of Pentablock Nanomicellar Formulations for Prostate Cancer Drug Delivery Systems

Abstract

This study is divided into three specific aims. Specific aim #1 focused on synthesis of pentablock co-polymer using monomers of L-lactide, ε-caprolactone and ethylene-glycol with varied molecular weights, (ii) characterization of the synthesized block co-polymers using X-ray diffraction crystallography (XRD), nuclear magnetic resonance (NMR), Fourier transform infra-red (FTIR) and critical micellar concentration (CMC). Specific aim #2 focused on: (i) preparation of nanomicelles with polymers synthesized in specific aim 1, loading hydrophobic paclitaxel drug or hydrophobic ion pairing complex(HIP) of doxorubicin molecules, and characterizing them for shape, size and polydispersity indices, (ii) conjugation of a ligand( PSMA antibody) on the surfaces of nanomicelles to ensure selectivity and targeted delivery, (iii) Optimization of parameters such as drug-to-polymer ratio on experimental design using JMP software and, (iv) determination of pentablock stability at different temperatures, and in vitro drug release of the drug-loaded nanomicellar formulation. Specific aim #3 was focused on: (i) assessing the safety of the synthesized pentablock copolymers by cytotoxicity studies on prostate cancer cell lines, (ii) determining cellular uptake and accumulation of the nanomicellar formulation from specific aim 2 in prostate cancer cell lines (PC-3), and (iii) evaluating the targetability of PSMA antibody conjugated nanomicelles in prostate cancer cells. Chapter # 1 outlines the overview of literature review on prostate cancer prevalence, available treatment options, as well as the current challenges faced by both the patients and the health practitioners during the treatment of prostate cancer. Chapter #2 discusses the common nanoformulations used in drug delivery systems. There are many promising drug delivery strategies such as liposomes, polymeric nanoparticles, nanomicelles, and combination of techniques have been studied in order to develop a sustained tumor drug delivery system. Nanomicelles (NM) enhance solubility and absorption of active pharmaceutical ingredients (APIs). Various polymers and non-polymers are being utilized to prepare nanomicellar formulations to achieve high absorption and delivery of drugs. In this study, we hypothesized that drug-loaded nanomicelles could be developed using pentablock copolymers for delivery of either paclitaxel or doxorubicin. Chapter #3 discusses how monomers of lactide, ε-caprolactone and polyethylene-glycol were utilized to prepare pentablock copolymer by ring opening technique. The pentablock nanomicelles (PBNM) were formulated by evaporation rehydration technique. Chapter #4 elucidates how PSMA antibody conjugated drug-loaded nanomicelles were prepared using MPEG--PLA-PCL-PLA-PEG-NH2 Pentablock copolymer for targeted delivery of hydrophobic anticancer drug (paclitaxel) to prostate cancer cells. The resultant pentablock nanomicelles were conjugated with PSMA antibody resulting in PTX-PBNM-Ab. XRD, FT-IR and the H-NMR analyses confirmed the structure of the pentablock copolymers. Chapter #5 discusses the preparation of a hydrophobic ion-paring complex (HIP complex) of doxorubicin using hydrophobic retinoic acid. The resultant hydrophobic (DOX-RA) complex was utilized to prepare drug-loaded nanomicelles by co-precipitation method The average sizes for PTX-PBNM, PTX-PBNM-Ab and DOX RA/PBNM were 20 nm ± 5.00nm, 45nm ± 2.5nm, 25.5nm ± 5.00nm, respectively, and ζ-potential for both PTX-PBNM and DOX-RA/PBNM was around zero, while PTX PBNM-Ab had -28mV. In vitro release studies revealed that pentablock nanomicelles released PTX at a slow first order rate. The DOX-RA/PBNM released doxorubicin slowly in phosphate buffer solution (PBS) at pH 7.4 compared to pH 5.5 and pH 4.0. Transmission electron microscopy analysis revealed well-defined spherical nanomicellar structure for all the types of pentablock nanomicelles. The in vitro cell uptake studies demonstrated that pentablock nanomicelles were well uptaken in the cells and a large amount of both PTX and doxorubicin were ferried into the cells.