Ion-Mediated Protein Stabilization on Nanoscopic Surfaces

Abstract

The emergence of nanoparticles in biomedical applications has made their interactions with proteins inevitable. Nanoparticles conjugated with proteins and peptide-based constructs form an integral part of nanotherapeutics and have recently shown promise in treating a myriad of diseases. The proper functioning of proteins is critical to achieve their biological functions. However, interface issues result in the denaturation of proteins, and the loss of orientation and steric hindrance can adversely affect the function of the conjugate. Furthermore, surface-induced denaturation also triggers protein aggregation, resulting in amyloid-like species. Understanding the mechanistic underpinnings of protein−nanoparticle interactions and controlling their interfacial characteristics are critical and challenging due to the complex nature of the conjugates. In this milieu, we demonstrate that ionic liquids can be suitable candidates for stabilizing protein−nanoparticle interactions by virtue of their excellent protein-preserving properties. We also probe the previously unexplored mechanism of ion-mediated stabilization of the protein molecules on the nanoparticle surface. The protein−nanoparticle conjugates consist of lysozyme and choline-based ionic liquids characterized by optical and electron microscopy techniques combined with surface-sensitive plasmon-enhanced Raman spectroscopy. Furthermore, atomistic molecular dynamics simulations of the conjugates delineate interfacial interactions of the protein molecules and the modulation by the ions, particularly the conformational changes and the dynamic correlation when the protein and specific ionic liquid molecules are adsorbed on the nanoparticle surface. The combined experimental and computational studies showed the synergistic behavior of the ions of the ionic liquids, specifically the orientation and coverage of the anions aided by the cations to control the surface interactions and hence the overall protein stability. These studies pave the way for using ionic liquids, particularly their biocompatible counterparts in nanoparticle-based complexes, as stabilizing agents for biomedical applications.

Recent Advances in Biocompatible Ionic Liquids in Drug Formulation and Delivery

“…The protein aggregation propensity reduces with increasing IL concentrations over an extended 365 days of storage, even under stress conditions. The same choline chloride IL was used to determine the mechanism by which lysozyme-nanoparticle interactions are stabilized, and this system was compared with other choline dihydrogen citrate bio-IL-based systems to investigate the role of anions in the ILs (Figure 5A) [54]. Bisht et al used a series of choline-based bio-ILs to investigate the stability of the chymotrypsin structure against thermal denaturation and revealed that choline acetate IL-containing chymotrypsin shows a high stabilizing capacity among all studied ILs and choline hydroxide solution [55].…”

Effects of acid dissociation and ionic solutions on the Aggregation of 2-pyrone-4,6-dicarboxylic acid

“…39 For instance, MD simulations have been used to investigate how ion-mediated interactions influence protein stabilization on nanoparticle surfaces. 40 Dai et al used MD simulations to investigate ion-mediated attractive interactions between DNA molecules and rationalized this attractive force through the formation of ion bridges. 41 Lewis et al…”

Photoactivated plasmonic nanohybrid fibers with prolonged trapping of excited charge carriers for SERS analysis of biomolecules

“…36 However, the attachment of the protein to the nanoparticle surface is critical for obtaining exquisite biochemical information, specifically from the surface of the protein, as the SERS enhancement diminishes exponentially from the surface of the plasmonic nanoparticles. 37 The electrons generated due to pre-irradiation also aid in this regard, as they help enhance the attachment of the protein molecules to the surface of the nanoparticles. For the first time, we demonstrate this alternate method of improving the surface attachment of proteins by activating cystine thiol groups similar to that employed in light assisted molecular immobilization (LAMI).…”