Overcoming Cytosolic Delivery Barriers Using Multifunctional Mesoporous Silica Nanoparticles: A Proposed Platform for Enzyme Replacement Therapy

Abstract

Efficient cytosolic delivery of therapeutic proteins remains a major challenge in modern drug delivery due to multiple biological barriers, including protein corona formation, rapid immune clearance, limited cellular uptake, endosomal entrapment, and lysosomal degradation. These barriers significantly reduce the therapeutic potential of intracellular protein therapies and enzyme replacement strategies. Mesoporous silica nanoparticles (MSNs) have emerged as promising nanocarriers because of their high surface area, tunable pore structure, excellent loading capacity, and versatile surface functionalization. As a proof-of-concept application, the proposed platform is intended for the targeted delivery of glycogen debranching enzyme in Glycogen Storage Disease Type III (GSD III), a rare inherited metabolic disorder characterized by abnormal glycogen accumulation due to enzyme deficiency. Although conceptual, this platform demonstrates the potential of combining nanotechnology with targeted intracellular delivery strategies to improve the effectiveness of enzyme therapies. The proposed system may also provide a versatile framework for future protein- and enzyme-based therapeutics requiring efficient cytosolic delivery. This work proposes a multifunctional MSN-based delivery platform designed to overcome major cytosolic delivery barriers. The proposed strategy incorporates PEGylation to reduce protein corona formation and prolong systemic circulation, GalNAc as a hepatocyte-targeting ligand to facilitate receptor-mediated uptake through the asialoglycoprotein receptor (ASGPR), and a pH-responsive moiety to promote endosomal escape and efficient cytosolic release of the therapeutic cargo. The integration of these modifications aims to enhance intracellular bioavailability while minimizing premature degradation.