Slowly-Dissolving Aqueous Suspensions of Functionalized Protein+Antibody PRINTRTM Particles for Therapeutic Applications

Developing an injectable sustained release formulation is an exciting alternative for overcoming the shortcomings associated with delivery of biopharmaceuticals. This can be particularly advantageous for protein based formulations that have low bioavailability due to their large molecular size and hydrophilic nature while being prone to enzymatic degradation. With an injectable controlled release formulation, drug concentration can be kept within the therapeutic window over an extended period of time and drug efficacy can be potentially improved. Moreover, local injection to the site of interest within the body can minimize the unwanted distribution of drug in unrelated organs and reduce the inherent toxicity associated with potent drugs.;Among variety of carriers, particulate systems are very well suited for delivering protein based pharmaceuticals. In this work, micro particles with specific size and shape are fabricated from bovine serum albumin (BSA) as a model protein using Particle Replication in Non-wetting Templates (PRINT). These particles are then rendered slowly-dissolving in aqueous media using a bifunctional chlorosilane (diisopropyldichlorosilane) that can act as a crosslinking agent. Mass spectrometric study of the reaction products of diisopropyldichlorosilane with individual ingredients of the particles confirmed that they are capable of reacting and forming chemical crosslinks. Energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) both corroborated that there is a direct correlation between the amount of silicon in the particles and reaction time.;We demonstrated that the dissolution rate of these particles is controlled by how long particles are exposed to chlorosilane and pH of the surrounding environment. Desilylation is expected to be the primary mechanism governing the dissolution of these particles. Circular dichroism spectroscopy proved that the fraction of BSA molecules released from the functionalized particles retain their secondary structure. Freeze-drying the functionalized particles in organic media allowed us to prepare a solvent-free formulation that could be reconstituted in aqueous media prior to administration. No evidence of toxicity was observed for the formulation when treating RAW macrophages and synovial fibroblasts with these functionalized slowly-dissolving particles.;Regional delivery through intra-articular (i.a.) route is an exciting method for delivering biological disease modifying anti-rheumatic drugs. However, benefits of local treatment can be hindered by poor retention of the therapeutic agent in the joint. Therefore, we investigated the advantage of this slowly-dissolving system in increasing the retention time of the model protein (BSA) in the murine joint. It was demonstrated that protein retention in the joint can be increased upon incorporation into these slowly-dissolving particles. Histological examination of the joint sections after i.a. injection, confirmed that the injected microparticles were delivered to the joint cavity. Furthermore, we demonstrated that the particles can encapsulate a model antibody (anti-ovalbumin) and thus can act as a delivery carrier for antibody based therapeutics. Viscosity measurements on the concentrated suspensions confirmed that the deliverable dose of these particles per single injection can be significantly increased depending on the pH requirements for the formulation and characteristics of the administration site.