Utilizing Inverse Emulsion Polymerization To Generate Responsive Nanogels for Cytosolic Protein Delivery

Abstract

Therapeutic biologics have various advantages over synthetic drugs in terms of selectivity, their catalytic nature and thus, therapeutic efficacy. These properties offer the potential for more effective treatments that may also overcome the undesirable side effects observed due to off-target toxicities of small-molecule drugs. Unfortunately, systemic administration of biologics is challenging due to cellular penetration, renal clearance and enzymatic degradation difficulties. A delivery vehicle that can overcome these challenges and deliver biologics to specific cellular populations has the potential for significant therapeutic impact. In this work, we describe a redox-responsive nanoparticle platform, which can encapsulate hydrophilic proteins and release them only in the presence of a reducing stimulus. We have formulated these nanoparticles using an inverse emulsion polymerization (IEP) methodology, yielding inverse nano-emulsions, or nanogels. We have demonstrated our ability to overcome the liabilities that contribute to activity loss by delivering a highly challenging cargo, functionally active caspase-3, a cysteine protease susceptible to oxidative and self-proteolytic insults, to the cytosol of HeLa cells by encapsulation inside a redox-responsive nanogel.

Micro and Nanogels for Biomedical Applications

“…Among the heterogenous polymerization methods, inverse microemulsion polymerization is one of the most commonly used chemical crosslinking technique where water-in-oil (w/o) emulsion is prepared simply by mixing continuous oil phase and aqueous phase containing water soluble substrates in the presence of oil soluble emulsifying agents at above their critical micelle concentration (CMC). Consequently, thermodynamically stable microemulsion droplets are formed to serve as reactors for micro and nano sized particle formation [56]. The pH, surfactant concentration, and feed ratio of the crosslinkers and used substrates in particles preparation are the most important parameters that have major effects on the particle size and distribution [57,58].…”

Functional Microgels: Recent Advances in Their Biomedical Applications

“…The concentration of reducing GSH in the cytosol is ≈2 × 10 −3 –10 × 10 −3 m as compared to the extracellular fluids having ≈2 × 10 −6 –20 × 10 −6 m . Hence, drug delivery vehicles comprised of disulfide bonds are particularly interesting due to their characteristic degradation under physically relevant reducing conditions …”

“…[23,96,97] The concentration of reducing GSH in the cytosol is ≈2 × 10 −3 -10 × 10 −3 m as compared to the extracellular fluids having ≈2 × 10 −6 -20 × 10 −6 m. [98] Hence, drug delivery vehicles comprised of disulfide bonds are particularly interesting due to their characteristic degradation under physically relevant reducing conditions. [99][100][101] Multifunctional PNIPAM-based microgels were fabricated by Zhang et al via precipitation method using (2-dimethylamino)ethyl methacrylate (DMAEMA) and 3-acrylamidephenylboronic acid (AAPBA) as comonomers along with BAC as degradable crosslinker. [102] Developed microgels were stable under physiological conditions (pH 7.4, 0.15 m NaCl, 37 °C).…”

Stable Formulations of Peptide-Based Nanogels

“…On the one hand, the inverse emulsion technique consists of the formation of a water-in-oil (W/O) emulsion via homogenization of an aqueous phase containing the Fmoc-Phe-Phe-OH (Fmoc-FF, N α -9-fluorenylmethoxycarbonyl-diphenylalanine) peptide with an oily phase containing a surfactant as a stabilizer. This methodology is very often used for the formulation of polymeric nanogels [ 20 ]. On the other hand, the top-down methodology involves the formulation of nanogel particles using a α,β-dehydrophenylalanine (ΔPhe) containing dipeptide, H-Phe-ΔPhe-OH (phenylalanine-α,β-dehydrophenylalanine) [ 21 ].…”