Bioconjugated Nanogels

Nanogels are otherwise called as nanocarriers for the encapsulation and delivery of biomolecules. Designing nanogels as delivery systems for biomolecules with a capacity to respond to the external physical and chemical signals like pH and temperature. Moreover, it has enhanced permeability and retention (EPR) effect, due to their extremely small size. There are many advances that have been developed in designing nanogels for various purposes. Some of them are as follows:

• Nanogels for intracellular delivery of genetic material - Nowadays, gene therapy designed for delivery of antisense oligodeoxynucleotides (ODNs), plasmid DNA (pDNA), siRNAs and micro RNAs (miRNAs) used in targeted inhibition of specific mRNA sequences has developed as one of the most favourable method to treat and diagnose diseases like cancer, neurodegenerative disorders and viral infections. However, the major tests in designing an intracellular gene delivery system exist in crossing the cell membranes without being premature degraded by endogenous enzymes and providing a controlled release of the genetic material into the cell nucleus without inducing cytotoxicity and an immune response following degradation.
• Nanogels for specific targeted protein delivery - The major problem in using proteins and peptides as therapeutic agents are the protein stabilization in delivery reservoirs at physiological pH values and temperatures and the proper design of protein carriers for the sustained and targeted delivery. One of the approaches in overcoming these limitations is to entrap proteins into hydrogel nanoparticles (nanogel), which can reduce denaturation of proteins by forming a colloidal stable complex with proteins at the nanometer scale (<50 nm).
• Bioconjugated hydrogel nanoparticle as vaccine delivery or adjuvant systems - Recently, multi-responsive polymeric nanogels have developed a new vaccine delivery system which is capable of initiating innate immune response or enhancing antigen delivery. Therefore, in the case of genetic material and protein encapsulation, nanogels intrinsic properties allow protecting vaccine antigens from degradation in vivo and, by bioconjugation with antibodies or specific ligands, could increase active targeting specificity. Among them, polysaccharide-based nanogels such as cationic cholesterol-bearing pullulan (cCHP) appear to be very appealing as vaccine delivery systems due to their great biocompatibility and the abundance in unprocessed sources.

Limitation of using nanogels as targeted delivery systems is represented by their low target site specificity. Therefore, by conjugation of nanogels or nanogel compounds with biomolecules such as ligands, proteins or other molecules having molecular recognition specificity, the specificity for targeted delivery will improve. Attachment of biomolecules allows a rapid internalization of nanogels into the cells through endocytosis.