Biotemplated Platinum Nanozymes: Synthesis, Catalytic Regulation and Biomedical Applications.

Platinum (Pt) nanozymes with multiple intrinsic enzyme-mimicking activities have attracted extensive attention in biomedical fields due to their high catalytic activity, ease of modification, and convenient storage. However, the Pt nanozymes synthesized by the traditional method often suffer from uncontrollable morphology and poor stability under physicochemical conditions, resulting in unsatisfactory catalytic behavior in practical applications. To optimize the catalytic ability, biological templates have been introduced recently, which can guide the deposition of platinum ions on their surface to form specific morphologies and then stabilize the resulting Pt nanozymes. Given the promising potential of biotemplated Pt nanozymes in practical applications, it is essential to conduct a systematic and comprehensive review to summarize their recent research progress. In this review, we first categorize the biological templates and discussed the mechanisms as well as characteristics of each type of biotemplate in directing the growth of Pt nanozyme. Factors that impact the growth of biotemplated Pt nanozymes are then analyzed, followed by summarizing their biomedical application. Finally, the challenges and opportunities in this field are outlined. This review article aims to provide theoretical guidance for developing Pt nanozymes with robust functionalities in biomedical applications.

The influence of digestive tract protein on cytotoxicity of polyvinyl chloride microplastics.

Microplastics in food and drinking water can enter the human body through oral exposure, posing potential health risks to the human health. Most studies on the toxic effects of microplastics have focused on aquatic organisms, but the effects of the human digestive environment on the physicochemical properties of microplastics and their potential toxicity during gastrointestinal digestion are often limited. In this study, we first studied the influence of interactions between digestive tract protein (α-amylase, pepsin, and trypsin) and microplastics on the activity and conformation of digestive enzymes, and the physicochemical properties of polyvinyl chloride microplastics (PVC-MPs). Subsequently, a simulated digestion assay was performed to determine the biotransformation of PVC-MPs in the digestive tract and the intestinal toxicity of PVC-MPs. The in vitro experiments showed that the protein structure and activity of digestive enzymes were changed after adsorption by microplastics. After digestion, the static contact angle of PVC-MPs was decreased, indicating that the hydrophilicity of the PVC-MPs increased, which will increase its mobility in organisms. Cell experiment showed that the altered physicochemical property of PVC-MPs after digestion process also affect its cytotoxicity, including cellular uptake, cell viability, cell membrane integrity, reactive oxygen species levels, and mitochondrial membrane potential. Transcriptome analyses further confirmed the enhanced biotoxic effect of PVC-MPs after digestion treatment. Therefore, the ecological risk of microplastics may be underestimated owing to the interactions of microplastics and digestive tract protein during biological ingestion.

A fast visual onsite method for detection and quantitation of food additives using an engineered metal nanohybrid-based catalyst.

Unsafe food additives pose a significant threat to global health, especially in developing countries. Many existing methods rely on clean laboratories, complicated optics equipment, trained personnel and lengthy detection time, which are not suitable for onsite food safety inspections in emergency situations, peculiarly in impoverished areas. In this paper, a fast and visual onsite method is designed for the detection and quantification of additives in food safety by engineering a nanohybrid (MoS2/SDBS/Cu-CuFe2O4)-based catalysis. Interestingly, the nanohybrid presents peroxidase-like mimetic activity toward the substrate containing 3,3',5,5'-tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2), which are then integrated simply into a detection kit. The blue oxidated TMB in this kit can be converted completely to colorless by some bio-molecule additives in commercial food, such as glutathione (GSH), cysteine (Cys), and ascorbic acid (AA). Remarkably, this process takes just less than 2 min and the detection limits are 2.8 nM, 5.5 nM and 47 nM, respectively. These results show excellent repeatability with a statistical analysis with (*P < 0.05) over 30 tests. Next, the images of the color changes can be captured clearly using a smartphone by red-green-blue (RGB) channels, which provides an opportunity for the development of field-operation device. Additionally, our approach is applied to some targets-indicative foods, showing a recovery range between 95.8 % and 104.2 %, offering an attractive and promising pathway for future practical food safety inspection applications. More importantly, this method can easily be extended to the detection of reducing substances in other analytical fields.

Integration of Hybridization Chain Reaction and Protein-Binding Amplification for Long-Term Imaging of Intracellular mRNA: Avoiding Signal Fluctuation.

Amplified nanoprobes based on hybridization chain reaction (HCR) have been widely developed for the detection of intracellular low abundance mRNA. However, the formed chain-like assembly decorated with fluorophore would be degraded rapidly by endogenous enzyme, resulting in failure of the long-term fluorescence imaging. To address this issue, herein, a composite signal-amplifying strategy that integrates HCR into protein-binding signal amplification (HPSA) was communicated for the in situ imaging of mRNA by avoiding signal fluctuation. Different from conventional HCR-based nanoprobes (HCR-nanoprobe), the HCR was used as the signal-triggered mode and the amplifying signal generated from in situ fluorophore-protein binding in cells, which can maintain high stability of the signal for a long time. As a proof-of-principle, a nanobeacon based on HPSA (HPSA-nanobeacon) was constructed to detect TK1 mRNA. Taking advantage of the double signal-amplifying mode, the endogenous TK1 mRNA was sensitively detected and the fluorescence signal was maintained for more than 8 h in HepG2 cells. The attempt in this work provides a new option to the current signal-amplifying strategy for sensing nucleic acid targets with high stability, significantly enhancing the acquisition of intracellular molecular information.

Pt-S bond stabilized DNAzyme nanosensor with thiol-resistance enabling high-fidelity biosensing.

Gold nanoparticles (Au NPs) have been widely utilized in developing DNAzyme-functionalized nanosensors, most of which were engineered by attaching the thiolated DNAzymes to Au NPs via Au-S bonding. However, the Au NP-DNAzyme nanosensors always suffer from signal distortion when applied in complex environment with abundant thiols, which poses challenge for practical applications. Here, we focus on addressing the root cause of the issue and propose to decorate the Au NPs with a thin layer of platinum, thus facilitating the conjugation of DNAzymes through Pt-S bonding, a thiol-resistant cross-linking. The Pt-S bond stabilized DNAzyme nanosensor effectively minimized false positive signals when detecting l-histidine in infant formulas, as compared to the Au-S stabilized counterpart. This innovative strategy holds promise for high-fidelity biosensing, improving the practical applicability of Au NP-based DNAzyme nanosensor.

Pt-Decorated Gold Nanoflares for High-Fidelity Phototheranostics: Reducing Side-Effects and Enhancing Cytotoxicity toward Target Cells.

Functionalized with the Au-S bond, gold nanoflares have emerged as promising candidates for theranostics. However, the presence of intracellular abundantly biothiols compromises the conventional Au-S bond, leading to the unintended release of cargoes and associated side-effects on non-target cells. Additionally, the hypoxic microenvironment in diseased regions limits treatment efficacy, especially in photodynamic therapy. To address these challenges, high-fidelity photodynamic nanoflares constructed on Pt-coated gold nanoparticles (Au@Pt PDNF) were communicated to avoid false-positive therapeutic signals and side-effects caused by biothiol perturbation. Compared with conventional photodynamic gold nanoflares (AuNP PDNF), the Au@Pt PDNF were selectively activated by cancer biomarkers and exhibited high-fidelity phototheranostics while reducing side-effects. Furthermore, the ultrathin Pt-shell catalysis was confirmed to generate oxygen which alleviated hypoxia-related photodynamic resistance and enhanced the antitumor effect. This design might open a new venue to advance theranostics performance and is adaptable to other theranostic nanomaterials by simply adding a Pt shell.

Lowering Entropic Barriers in Triplex DNA Switches Facilitating Biomedical Applications at Physiological pH.

Triplex DNA switches are attractive allosteric tools for engineering smart nanodevices, but their poor triplex-forming capacity at physiological conditions limited the practical applications. To address this challenge, we proposed a low-entropy barrier design to facilitate triplex formation by introducing a hairpin duplex linker into the triplex motif, and the resulting triplex switch was termed as CTNSds. Compared to the conventional clamp-like triplex switch, CTNSds increased the triplex-forming ratio from 30 % to 91 % at pH 7.4 and stabilized the triple-helix structure in FBS and cell lysate. CTNSds was also less sensitive to free-energy disturbances, such as lengthening linkers or mismatches in the triple-helix stem. The CTNSds design was utilized to reversibly isolate CTCs from whole blood, achieving high capture efficiencies (>86 %) at pH 7.4 and release efficiencies (>80 %) at pH 8.0. Our approach broadens the potential applications of DNA switches-based switchable nanodevices, showing great promise in biosensing and biomedicine.

Portable Detection of Lysine Acetyltransferase Activity in Lung Cancer Cells Based on a Miniature Electrochemical Sensor.

The detection of lysine acetyltransferases is crucial for diagnosing and treating lung cancer, highlighting the necessity for highly efficient detection methods. We developed a portable, highly accurate, and sensitive technique using fast-scan cyclic voltammetry (FSCV) to determine the activity of the lysine acetyltransferase TIP60, employing a novel miniature electrochemical sensor. This approach involves a compact electrochemical cell, merely 3 mm in diameter, that holds solutions up to 50 µL, equipped with a conductive indium tin oxide working electrode. Uniquely, this system operates on a two-electrode model compatible with the FSCV, obviating the traditional requirement for a reference electrode. The system detects TIP60 activity through the continuous generation of CoA molecules that engage in reactions with Cu(II), thereby significantly improving the accuracy of the acetylation analysis. Remarkably, the detection limit achieved for TIP60 is notably low at 3.3 pg/mL (S/N = 3). The results show that the reversible dynamic acetylation can be effectively regulated by inhibitor incubation and glucose stimulation. This cutting-edge strategy enhances the analysis of a broad spectrum of biomarkers by modifying the responsive unit, and its miniaturization and portability significantly amplify its applicability in biomedical research, promising it to be a versatile tool for early diagnostic and therapeutic interventions in lung cancer.

One-step, reagent-free construction of nano-enzyme as visual and reusable biosensor for oxidase substrates.

The substrates of oxidase are biologically essential substances that are closely associated with human physiological health. However, current biosensing methods suffer from tough recyclability and undesired denaturation of enzyme due to impurity interference. Herein, we have developed a visual and reusable biosensor for detecting substrate using glucose oxidase (GOx) as a model oxidase. GOx was immobilized onto gold nanoparticles (AuNPs) at -20 °C in one step without additional reagents. The resulting nano-enzyme generated coloimetric signals by coupling with horseradish peroxidase (HRP) using TMB as the substrate. Our results demonstrated that the immobilized GOx exhibited satisfactory sensitivity (0.68 µM) for glucose detection and higher inherent stability than free GOx under harsh conditions, enabling reliable detection of glucose in complex fluids (colored beverages and saliva). Furthermore, the nano-enzyme retained 80 % activity even after four cycles of catalytic oxidation. This strategy constructs a universal biosensor for substrates with nano-enzyme which rely only on intrinsic cysteine within the oxidase while avoiding functional handle modification.