Ionic Liquid-Modified Gold Nanoparticles for Enhancing Antimicrobial Activity and Thermal Stability of Enzymes

Abstract

The synthesis of nanoparticles using ionic liquids (ILs) has attracted intensive research; however, synthesis and surface tailoring of gold nanoparticles (AuNPs) using ILs for enzyme immobilization have not yet been reported. Herein, we synthesized the various IL-modified AuNPs using different ILs, which are having common cation 1-ethyl-3-methyl-imidazolium (EMIM) and variable anions [BF 4−1 (AuNP-IL1), (CH 3 OSO 3 ) −1 (AuNP-IL2), (CH 3 CH 2 OSO 3 ) −1 (AuNP-IL3), and Cl −1 (AuNP-IL4)] by reduction of gold salt. The formation of IL modified AuNPs has been confirmed using UV−vis, zeta-potential, FTIR, and transmission electron microscopy (TEM). Thereafter, the centrifuged IL-modified AuNPs are being immobilized with a lysozyme (Lyz) enzyme to evaluate the effect of different AuNP covering groups (capping agent and IL's anions) for Lyz microbial activity, thermal and structural stabilities through interaction studies, spectroscopic techniques, and morphology investigation by TEM. AuNP-IL1 has increased the microbial activity of Lyz up to 2.6 fold at the concentration of 4 nM, and AuNP-IL2 is highly efficient to dextrously preserve enzyme activity against packaging for 4 weeks. The higher Michaelis−Menten constant (K M ) has been observed for Lyz immobilized in the AuNP-IL2 due to higher binding with the AuNP-IL2. Apparently, the higher specific constant (K cat /K M ) of immobilized Lyz has been observed in the case of AuNP-IL3 and shows more specific binding of Lyz with this particular IL-mediated AuNPs. The significant thermal stability enhancement about 8.11 °C is observed for transition temperature (T m ) of Lyz in the presence of sulfur group-containing IL-modified AuNPs like AuNP-IL2 and AuNP-IL3, which depends on the specific interacting ability of these AuNPs with Lyz. Therefore, the study reveals the variant character of sulfur-containing IL-modified AuNPs for higher activity and thermal and structural stability of Lyz. Surprisingly, this has created a way to monitor sulfur and hydrophobic interactions on AuNPs for enzyme immobilization through means of controlling surface modifications and interactions.

Unprecedented enhancement and preservation of the peroxidase activity of cytochrome-c packaged with ionic liquid-modified gold nanoparticles by offsetting temperature and time stresses

“…Lastly, the zeta potential result concludes that with the increase in the concentration of AuNPs, the surface charge of the Cyt- c -AuNPs systems change to positive values with higher values for higher concentrations of Cyt- c -AuNP-IL3. The results surmount the biocompatibility of IL-mediated AuNPs from the previous study 34 to next and advanced levels subsiding the effects of higher temperature and long-term preservation on the activity and stability of enzymes.…”

“…33 In the previous work, our group has synthesized AuNPs using 1-ethyl-3-methyl-imidazolium (EMIM)-based ILs with various anions such as tetrafluoroborate [BF 4 ] À1 for AuNP-IL1, methylsulfate [CH 3 OSO 3 ] À1 for AuNP-IL2, ethylsulfate [C 2 H 5 OSO 3 ] À for AuNP-IL3 and chloride [Cl] À1 for AuNP-IL4, and therefore, enhanced the immobilization of the lysozyme enzyme, in turn enhancing the activity at room temperature. 34 Although, in the previous study, a higher enhancement in the activity has been observed along with preferential binding by the Michaelis-Menten constant and specific constant, the effect of multiple stresses such as temperature and long-term preservation with time has not been witnessed. Therefore, in the current study, the activity and thermal stability of Cyt-c were enhanced competitively in the presence of IL-mediated AuNPs against temperature change up to 90 1C and long-time preservation for 45 days.…”

Melamine-derived N-rich C-entrapped Au nanoparticles for sensitive and selective monitoring of dopamine in blood samples

“…Additionally, the peak at 1409 cm −1 is assigned to the asymmetric and symmetric C–H scissoring vibrations of the CH 3 –N + moiety and clearly shows the presence of H-bonding between AuNPs and IL, which is in accordance with the reported literature. 30 The IL contributes to the π-electron density of the system enhancing the speed of electron transfer due to a smooth conductive pathway. The results of UV and Raman spectra confirm these interactions within the system.…”

Current understanding and insights towards protein stabilization and activation in deep eutectic solvents as sustainable solvent media

“…8,[27][28][29][30][31] Our research group has been diligently studying the exposure of various protein structures to numerous co-solvents to get an outlook towards the stability of the biomolecules in these solvents. 1,[32][33][34][35][36][37][38] Recently, with the emergence of the neoteric solvents, DESs, we have investigated the protein friendly behaviour in these solvents. There are only a handful of reports available related to protein stability and refolding ability in DESs.…”