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Using nanomaterials is a novel strategy to eliminate drug resistance against bacteria. Nanoparticles with metal sites show antimicrobial activities that counteract or obstruct antibiotic-resistant mechanisms expressed by the pathogens. Here, a nanocomposite based on mesoporous silica nanoparticles with active sites of silver, and a combination of imipenem and meropenem as antibiotic drugs, was synthesized and characterized using different physicochemical methods. The antibacterial assessments exhibited sensitivity by Staphylococcus aureus ( S. aureus ), Klebsiella pneumoniae ( K. pneumoniae ) and Escherichia coli ( E. coli ) toward the synthesized composite, which showed a suitable safety profile in human cells. This composite has an excellent synergic mechanism based on reactive oxygen species (ROS) to kill bacteria due to penetrating the microbial membrane. In addition, this composite is resistant to hydrolysis by plasmids and chromosomally mediated β-lactamases. This nanocomposite showed extraordinary antiseptic power against Gram-positive and Gram-negative microbes.

In an attempt to explore the significance of inorganic mimetic enzymes as sensors, this study introduces a naked-eye analytical sensing platform for the detection of L-cysteine (cys), mercury ions (Hg 2+ ) based on (turn off/turn-on) catalytic activity of zinc and cobalt grafted mesoporous silica nanoparticles (MSNs). To this end, Zn-MSN and Co/Zn-MSN catalysts were synthesized and characterized using XRD, FT-IR, FESEM, TEM, and nitrogen adsorption-desorption methods. Then, using the intrinsic peroxidase-like activity of as-synthesized samples, the oxidation reactions of the chromogenic substrate (2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS)) was designed using H 2 O 2 , which produced green colored cation radical of ABTS. Considering the high peroxidase-like activity of Co/Zn-MSN in comparison to Zn-MSN, it was employed to detect cys and then Hg 2+ . The results indicated that the strong interaction between cys and Co/Zn-MSN was proved by a limit of detection (LOD) down to 0.24 nM and the linear relationship from 0.8-50 nM (turn off). Given the fact that Hg 2+ has a high-affinity tendency to combine with cys, we were suggested a novel colorimetric path for sensing of Hg 2+ in the presence of cys (turn on). Based on this method, LOD was found 0.17 nM with the linear range of 0.57-50 nM. Taken together, results showed that the as-prepared catalysts are superior to other nanoparticles as a sensor to measure the target molecules in biological monitoring and clinical diagnostics.

Over the past decade, there has been a dramatic increase in the number of studies focused on sensors for cysteine (Cys) as a crucial factor in physiological function and disease diagnosis. Among those sensors, nanomaterial-based peroxidase mimetics have received particular attention from researchers. This study introduces a new series of mesoporous silica nanoparticles (MSNs) incorporated with iron and cobalt (Co/Fe-MSN) with a molar ratio of Si/Fe = 10 and cobalt species at 1, 3, and 5 wt% that have great potential in the sensing application. These nanomaterial characterization was investigated by FTIR spectroscopy, SEM, TEM, XRD, and nitrogen adsorption-desorption. The peroxidase activity of these nanomaterials was studied through kinetic analysis. The findings revealed that Co/Fe-MSN (1%) showed higher peroxidatic activity than the others towards the common chromogenic substrate 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) diammonium salt. Based on the enzymatic activity of Co/Fe-MSN (1%), a colorimetric sensing platform was designed to detect H2O2 and Cys. The limit of detection (LOD) for H2O2 and Cys was determined to be 1.1 μM and 0.89 nM, respectively. The results indicated that the proposed enzyme mimic exhibited excellent potential as a sensor in medical diagnostics and biological systems.