Nanoparticle Functionalization: Implications in Corona-Modulated Biological Applications

Abstract

Increasing growth and necessity of nanotechnology has brought risk to flora and fauna of niche for nanoparticle (NP)-mediated effects, including mortality. Additionally, over the last decade, there have been reports on heavy metal remediation by microbes and plants into harmless forms, which they, some of them, either store or secrete in the form of biocompatible nanocrystals stabilized with host’s biological moieties. The findings have been exploited, here, to fabricate metal nanoparticle with natural moieties as surface functionalities, and investigated for wide range of potential nanoparticle mediated biological applications, like antimicrobial, cytocompatible and adjuvant applications. The NP, when administered in biological milieu, tends to further bind a variety of biomolecules, especially proteins, forming an interfacial corona that provides biological identity to NP. The adopted corona in new biological milieu is anticipated to affect the adsorbed protein conformation depending upon the interaction pattern at the interface, as explored in the thesis using bovine lactoferrin (BLf) and Bacillus anthracis protective antigen (PA) as protein models. BLf shares 69% sequence homology with human lactoferrin, and is a well-studied protein for its conformation. On the other hand, PA protein is a non-virulent factor of anthrax toxin of proteinaceous nature that constitutes the major component of adjuvant vaccine adsorbed (AVA) against anthrax, and has anionic interface unlike BLf. The thesis, mainly, discussed two metal nanoparticle interfaces in this context, i.e. silver nanoparticle (AgNP) and aluminum nanoparticle (AlNP). Upon analyzing the cytotoxic property of the nanoparticles against different spectrum of eukaryotic and prokaryotic cells, thesis investigated change in protein conformation, when it is adsorbed as hard/soft corona, and subsequent effects on the protein function. The interactions of BLf with AgNP, leading to the protein adsorption onto AgNP interface, were mainly contributed by van der Waals interactions and hydrogen bonds. Besides retaining the bacteriostatic function, BLf-adsorbed AgNP (BLf-AgNP) showed relatively lesser cytotoxicity, despite of enhanced internalization in THP-1 cell compared to bare AgNP. In the end, the thesis discusses effect of functionalized AgNP and AlNP interfaces on conformational dynamics of PA, where the interface, depending upon the surface functionalities, showed contrasting effects on PA aggregation propensity. Nevertheless, the biofabricated AlNP (bAlNP) and BLf-AgNP proved better adjuvant for PA-mediated immunization, in vivo. PA adsorbed as soft corona onto bAlNP showed to trigger better humoral and cellular immune responses with enhanced interleukins level in spleen, especially IL4, IL10 and IFN-, compared to immunization with commercially available adjuvant-antigen formulation or with only antigen. Thus, the thesis altogether outlines the importance of surface functionalities in biofabricated metal nanoparticles for its potential prophylactic and therapeutic applications