Expanded mesoporous silica-encapsulated ultrasmall Pt nanoclusters as artificial enzymes for tracking hydrogen peroxide secretion from live cells

Decorating Zirconium on Graphene Oxide to Design a Multifunctional Nanozyme for Eco-Friendly Detection of Hydrogen Peroxide

Peroxidase enzymes are crucial in analytical chemistry owing to significant peroxide analytes and their key role in hydrogen peroxide (H2O2) detection. Therefore, exploiting appropriate catalysts for the peroxidase like reactions has become crucial for achieving desired analytical performance. Zirconium (Zr) has attracted growing interest, as a safe and stable potential eco-friendly catalyst for various organic transformations that address increasing environmental challenges. Hence, aiming at fast, sensitive and selective optical detection of H2O2, a colorimetric platform is presented here, based on the excellent peroxidase enzyme-like activity of Zr decorated on graphene oxide (GO). The synergistic effect achieved due to intimate contact between an enzyme like Zr and the high surface area 0f GO ensures efficient electron transfer that increases the chemical and catalytic activity of the composite and advances the decomposition of H2O2 into hydroxyl radicals. The designed probe, thus, efficiently catalyzes the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB), via hydroxyl radicals, thereby transforming the colorless TMB into blue oxidized TMB within 2 min. The catalytic mechanism of the Zr-GO enzyme mimic is proposed herein and verified using a fluorescent probe terephthalic acid (TA) and other scavenger experiments. The multifunctional optical probe allows sensitive and highly selective recognition of H2O2 in a linear range from 100 to 1000 µM with a low detection limit of 0.57 µM. Essentially, the direct accessibility of Zr prevents having to use the complicated preparation and purification procedures mostly practiced for conventional biozymes and nanozymes. The devised method offers several gains, including being green and an inexpensive catalyst, having lower LOD, being fast, cost-effective and sensitive, and having selective work-up procedures.

Nanoarchitectured prototypes of mesoporous silica nanoparticles for innovative biomedical applications

Despite exceptional morphological and physicochemical attributes, mesoporous silica nanoparticles (MSNs) are often employed as carriers or vectors. Moreover, these conventional MSNs often suffer from various limitations in biomedicine, such as reduced drug encapsulation efficacy, deprived compatibility, and poor degradability, resulting in poor therapeutic outcomes. To address these limitations, several modifications have been corroborated to fabricating hierarchically-engineered MSNs in terms of tuning the pore sizes, modifying the surfaces, and engineering of siliceous networks. Interestingly, the further advancements of engineered MSNs lead to the generation of highly complex and nature-mimicking structures, such as Janus-type, multi-podal, and flower-like architectures, as well as streamlined tadpole-like nanomotors. In this review, we present explicit discussions relevant to these advanced hierarchical architectures in different fields of biomedicine, including drug delivery, bioimaging, tissue engineering, and miscellaneous applications, such as photoluminescence, artificial enzymes, peptide enrichment, DNA detection, and biosensing, among others. Initially, we give a brief overview of diverse, innovative stimuli-responsive (pH, light, ultrasound, and thermos)- and targeted drug delivery strategies, along with discussions on recent advancements in cancer immune therapy and applicability of advanced MSNs in other ailments related to cardiac, vascular, and nervous systems, as well as diabetes. Then, we provide initiatives taken so far in clinical translation of various silica-based materials and their scope towards clinical translation. Finally, we summarize the review with interesting perspectives on lessons learned in exploring the biomedical applications of advanced MSNs and further requirements to be explored.

Chiral FexCuySe nanoparticles as peroxidase mimics for colorimetric detection of 3, 4-dihydroxy-phenylalanine enantiomers

L-3,4-dihydroxy-phenylalanine (L-dopa) is the most widely used drug in Parkinson's disease treatment. However, development of cost-effective and high-throughput sensors to accurate enantioselective discrimination of L-dopa and D-dopa remains challenging to date. Herein, on the basis of the peroxidase-mimic activity of chiral Fe_xCu_ySe nanoparticles, we demonstrated a novel colorimetric sensor for determination of chiral dopa. The surface chiral ligand, L/D-histidine (L/D-His), endowed the nanozymes with enantioselectivity in catalyzing the oxidation of dopa enantiomers. According to the values ofk_cat/K_m, the efficiency of L-His modified nanoparticles (L-Fe_xCu_ySe NPs) towards L-dopa was 1.56 times higher than that of D-dopa. While, D-His can facilely reverse the preference of the nanozyme to D-dopa. On the basis of high catalytic activity and enantioselectivity of L-Fe_xCu_ySe NPs in oxidation of L-dopa, the L-Fe_xCu_ySe NPs-based system can be utilized for detection of L-dopa. The linear ranges for L-dopa determination were 5μM-0.125 mM and 0.125 mM-1 mM with a detection limit of 1.02μM. Critically, the developed sensor has been successfully applied in the quality control of clinical used L-dopa tablets. Our work sheds light on developing simple and sensitive chiral nanomaterials-based sensors for drug analysis.

Fluorescence-active and peroxidase-like expanded mesoporous silica-encapsulated ultrasmall Pt nanoclusters: a novel colorimetric/fluorescent dual-mode nanosensor for sensitive detection of mercury in medicinal and edible Pueraria lobata

A novel colorimetric/fluorescent dual-mode nanosensor for Hg²⁺ detection was constructed using expanded mesoporous silica (EMSN)-encapsulated ultrasmall platinum nanoclusters (EMSN@Pt NCs) with improved peroxidase-like and stable fluorescent activities. The sensing technique was based on the mechanism that the peroxidase mimetic activity and fluorescence intensity of EMSN@Pt NCs can be inhibited in the presence of Hg²⁺. In this sensing platform, a linear range of 5-50 nM with a detection limit of 1.78±0.38 nM and quantification limit of 5.93 nM was obtained via fluorescent analysis. A linear calibration curve from 0.25 to 200 nM with a detection limit of 8.25±0.51 nM and quantification limit of 27.47 nM was achieved via colorimetric analysis. The proposed dual-mode probe possesses excellent selectivity and reliability for Hg²⁺ detection, which can function as an efficient nanosensor for the quantitative determination of Hg²⁺ in Pueraria lobata.

A Brief Overview of Recent Progress in Porous Silica as Catalyst Supports

Porous silica particles have shown applications in various technological fields including their use as catalyst supports in heterogeneous catalysis. The mesoporous silica particles have ordered porosity, high surface area, and good chemical stability. These interesting structural or textural properties make porous silica an attractive material for use as catalyst supports in various heterogeneous catalysis reactions. The colloidal nature of the porous silica particles is highly useful in catalytic applications as it guarantees better mass transfer properties and uniform distribution of the various metal or metal oxide nanocatalysts in solution. The catalysts show high activity, low degree of metal leaching, and ease in recycling when supported or immobilized on porous silica-based materials. In this overview, we have pointed out the importance of porous silica as catalyst supports. A variety of chemical reactions catalyzed by different catalysts loaded or embedded in porous silica supports are studied. The latest reports from the literature about the use of porous silica-based materials as catalyst supports are listed and analyzed. The new and continued trends are discussed with examples.

MOF-derived porous ZnO-Co3O4 nanocages as peroxidase mimics for colorimetric detection of copper(ii) ions in serum

Sensitive detection of copper ions (Cu²⁺) in biological samples is extremely important since an abnormal level of Cu²⁺ is linked with many diseases. Herein, we demonstrated a novel turn-on colorimetric sensor for selective detection of Cu²⁺ both in buffered solution and serum samples based on porous bimetallic transition metal oxide nanocages (ZnO-Co₃O₄ NCs) as peroxidase mimics. The ZnO-Co₃O₄ NCs were prepared by using ZnCo-zeolitic-imidazolate-framework (ZnCo-ZIF) as precursors via direct calcination. With the high peroxidase-like activity, the obtained ZnO-Co₃O₄ NCs can catalyze the oxidation of tetramethylbenzidine (TMB) in the presence of H₂O₂ to form a blue colored product. The inhibition effect of cysteine (Cys) on the catalytic activity of ZnO-Co₃O₄ NCs and its strong binding ability toward Cu²⁺ enabled the ZnO-Co₃O₄ NCs/Cys system to be utilized for sensitive detection of Cu²⁺, in which the catalytic activity of ZnO-Co₃O₄ NCs/Cys can be recovered by the introduction of Cu²⁺ with an obvious color change of the solution. The linear range for Cu²⁺ determination was 2 to 100 nM with a detection limit of 1.08 nM. More importantly, this colorimetric sensor has been successfully applied to detect Cu²⁺ in serum without pretreatment. Our findings are expected to expand the scope of application of nanozyme and shed light on early disease diagnosis.