Polymeric Micelles as Carriers for Nerve-Highlighting Fluorescent Probe Delivery.

Nerve damage during surgery is a common morbidity experienced by patients that leaves them with chronic pain and/or loss of function. Currently, no clinically approved imaging technique exists to enhance nerve visualization in the operating room. Fluorescence image-guided surgery has gained in popularity and clinical acceptance over the past decade with a handful of imaging systems approved for clinical use. However, contrast agent development to complement these fluorescence-imaging systems has lagged behind with all currently approved fluorescent agents providing untargeted blood pool information. Nerve-specific fluorophores are known, however translations of these agents to the clinic has been complicated by their lipophilic nature, which necessitates specialized formulation strategies for successful systemic administration. To date the known nerve-specific fluorophores have only been demonstrated preclinically due to the necessity of a dimethyl sulfoxide containing formulation for solubilization. In the current study, a polymeric micellar (PM) formulation strategy was developed for a representative nerve-specific fluorophore from the distyrylbenzene family, BMB. The PM formulation strategy was able to solubilize BMB and demonstrated improved nerve-specific accumulation and fluorescence intensity when the same fluorophore dose was administered to mice utilizing the previous formulation strategy. The success of the PM formulation strategy will be important for moving toward clinical translation of these novel nerve-specific probes as it is nontoxic and biodegradable and has the potential to decrease the necessary dose for imaging while also improving the safety profile.

Preparation and Characterization of Individual and Multi-drug Loaded Physically Entrapped Polymeric Micelles.

Amphiphilic block copolymers like polyethyleneglycol-block-polylactic acid (PEG-b-PLA) can self-assemble into micelles above their critical micellar concentration forming hydrophobic cores surrounded by hydrophilic shells in aqueous environments. The core of these micelles can be utilized to load hydrophobic, poorly water soluble drugs like docetaxel (DTX) and everolimus (EVR). Systematic characterization of the micelle structure and drug loading capabilities are important before in vitro and in vivo studies can be conducted. The goal of the protocol described herein is to provide the necessary characterization steps to achieve standardized micellar products. DTX and EVR have intrinsic solubilities of 1.9 and 9.6 µg/ml respectively Preparation of these micelles can be achieved through solvent casting which increases the aqueous solubility of DTX and EVR to 1.86 and 1.85 mg/ml, respectively. Drug stability in micelles evaluated at room temperature over 48 hr indicates that 97% or more of the drugs are retained in solution. Micelle size was assessed using dynamic light scattering and indicated that the size of these micelles was below 50 nm and depended on the molecular weight of the polymer. Drug release from the micelles was assessed using dialysis under sink conditions at pH 7.4 at 37 (o)C over 48 hr. Curve fitting results indicate that drug release is driven by a first order process indicating that it is diffusion driven.

Antiangiogenic effect of docetaxel and everolimus as individual and dual-drug-loaded micellar nanocarriers.

PURPOSE: The in vitro inhibitory effect of Docetaxel (DTX) and Everolimus (EVR) alone and together in poly(ethylene glycol)-block-poly(D,L-lactic acid) (PEG-b-PLA) nanocarriers on angiogenic processes and acute toxicity in mice was evaluated. METHODS: PEG-b-PLA DTX and/or EVR nanocarriers were characterized for size, drug loading, stability, and drug release. Cell proliferation, tubule formation, and migration studies were performed in Human Umbilical Vein Endothelial Cells (HUVEC) and Maximum Tolerated Doses (MTD) studies were in mice. RESULTS: DTX and EVR loading was 1.93 and 2.00 mg/mL respectively with similar solubilities for dual-drug micelles. All micelles were below 30 nm with diffusion controlled drug release. The IC50 for DTX, EVR micelles were, 6.80 ± 0.67, 18.57 ± 2.86 and 0.65 ± 0.11 nM respectively with a synergistic inhibitory effect for dual-drug nanocarriers. Significant inhibition of tube formation occurred upon treatment with dual-drug nanocarriers as compared to individual micelles. EVR presence in dual-drug nanocarriers was able to significantly increase the inhibition of the migration of HUVEC by DTX. The MTDs for EVR, DTX and dual-drug micelles were 50, 30 and 20 mg/kg for each respectively. CONCLUSIONS: DTX-EVR dual-drug nanocarriers have antiangiogenic effects in vitro mediated through cellular angiogenic process and possess clinically relevant MTD.