Nanoparticle-Ligand Conjugations for Targeted Drug Delivery: Processing and Applications

Abstract

Targeted nanoparticles (NPs) have been recognized as promising vectors to deliver medicines. The attachment of targeting molecules to the NP surface offers several advantages over traditional drug delivery, including smaller systemic drug dosages, increased concentration of the drug at the necessary sites, and reduced side effects. Thus, targeted NPs have the potential to become an integral part of high impact treatments. Through the use of para-nitrophenyl activated ester-amine chemistry (pNP), the conjugation of several ligands to NP surfaces was explored, including bovine serum albumin (BSA), Alexa Fluor 350 (AF350), and anti-Müllerian inhibiting substance type II receptor (anti-MISIIR) antibody. As a serum protein, BSA posed significant challenges because of its binding properties. Ultimately, NP-BSA conjugates could not be quantified due to nonspecific adsorption, but several underlying phenomena of NP processing were elucidated. In the case of protein ligands such as BSA, commonly used methods of purification such as dialysis and centrifugal filtration were inadequate to separate NP-ligand conjugates and unreacted ligands under the reaction conditions used. Centrifugation of NPs and decanting of the supernatant was determined to be an effective method to purify NP-ligand conjugates. Some NP formulations, such as those in which the NP shell has a reduced amount of polyethylene glycol (PEG), are also vulnerable to aggregation by bulk association of the hydrophobic core. In particular, disturbances of the air-liquid interfaces contributed to aggregation in some formulations, and reduction of agitation was shown to mitigate the issue. Alternatively, BSA may be added as an excipient to prevent NP aggregation, as long as the protein does not interfere with the conjugation chemistry. Conjugation trials with anti-MISIIR were successfully completed. Both the extent of conjugation and the separation of unconjugated anti-MISIIR were confirmed by absorbance measurements at 280 nm. This system is a promising tool to deliver Müllerian inhibiting substance to ovarian cancer cells, and further work will be done to determine its capabilities in inhibiting ovarian cancer growth. NP targeting is a promising tool for drug delivery. Further studies in the conjugation of targeting molecules have the potential to create high impact, socially relevant medicines.