Overcoming Cytosolic Delivery Barriers of Proteins Using Denatured Protein-Conjugated Mesoporous Silica Nanoparticles

Intracellular delivery of therapeutic proteins has increased
advantages
over current small-molecule drugs and gene therapies, especially in
therapeutic efficacies for a broad spectrum of diseases. Hence, developing
the protein therapeutics approach provides a needed alternative. Here,
we designed a mesoporous silica nanoparticle (MSN)-mediated protein
delivery approach and demonstrated effective intracellular delivery
of the denatured superoxide dismutase (SOD) protein, overcoming the
delivery challenges and achieving higher enzymatic activity than native
SOD-conjugated MSNs. The denatured SOD-conjugated MSN delivery strategy
provides benefits of reduced size and steric hindrance, increased
protein flexibility without distorting its secondary structure, exposure
of the cell-penetrating peptide transactivator of transcription for
enhanced efficient delivery, and a change in the corona protein composition,
enabling cytosolic delivery. After delivery, SOD displayed a specific
activity around threefold higher than in our previous reports. Furthermore,
the in vivo biosafety and therapeutic potential for neuron therapy
were evaluated, demonstrating the biocompatibility and the effective
antioxidant effect in Neuro-2a cells that protected neurite outgrowth
from paraquat-induced reactive oxygen species attack. This study offers
an opportunity to realize the druggable possibility of cytosolic proteins
using MSNs.