In situ biosynthesis of ultrafine metal nanoparticles within a metal-organic framework for efficient heterogeneous catalysis

Ultrahigh Enzyme Loading Metal-Organic Frameworks for Deep Tissue Pancreatic Cancer Photoimmunotherapy

Protein drugs hold promise in treating multiple complex diseases, including cancer. The priority of protein drug application is precise delivery of substantial bioactive protein into tumor site. Metal-organic-framework (MOF) is widely considered as a promising carrier to encapsulate protein drug owing to the noncovalent interaction between carrier and protein. However, limited loading efficiency and potential toxicity of metal ion in MOF restrict its application in clinical research. Herein, a tumor targeted collagenase-encapsulating MOF via protein-metal ion-organic ligand coordination (PMOCol ) for refining deep tissue pancreatic cancer photoimmunotherapy is developed. By an expedient method in which the ratio of metal ion, histidine residues of protein and ligand is precisely controlled, PMOCol is constructed with ultrahigh encapsulation efficiency (80.3 wt%) and can release collagenase with high enzymatic activity for tumor extracellular matrix (ECM) regulation after reaching tumor microenvironment (TME). Moreover, PMOcol exhibits intensively poorer toxicity than the zeolitic imidazolate framework-8 biomineralized protein. After treatment, the pancreatic tumor with abundant ECM shows enhanced immunocyte infiltration owing to extracellular matrix degradation that improves suppressive TME. By integrating hyperthermia agent with strong near-infrared absorption (1064 nm), PMOCol can induce acute immunogenicity to host immunity activation and systemic immune memory production to prevent tumor development and recurrence.

Protein encapsulation of nanocatalysts: A feasible approach to facilitate catalytic theranostics

Enzyme-mimicking nanocatalysts, also termed nanozymes, have attracted much attention in recent years. They are considered potential alternatives to natural enzymes due to their multiple catalytic activities and high stability. However, concerns regarding the colloidal stability, catalytic specificity, efficiency and biosafety of nanomaterials in biomedical applications still need to be addressed. Proteins are biodegradable macromolecules that exhibit superior biocompatibility and inherent bioactivities; hence, the protein modification of nanocatalysts is expected to improve their bioavailability to match clinical needs. The diversity of amino acid residues in proteins provides abundant functional groups for the conjugation or encapsulation of nanocatalysts. Moreover, protein encapsulation can not only improve the overall performance of nanocatalysts in biological systems, but also bestow materials with new features, such as targeting and retention in pathological sites. This review aims to report the recent developments and perspectives of protein-encapsulated catalysts in their functional improvements, modification methods and applications in biomedicine.

Exploration of Microbial Factories for Synthesis of Nanoparticles - A Sustainable Approach for Bioremediation of Environmental Contaminants

The nanomaterials synthesis is an intensifying research field due to their wide applications. The high surface-to-volume ratio of nanoparticles and quick interaction capacity with different particles make them as an attractive tool in different areas. Conventional physical and chemical procedures for development of metal nanoparticles become outmoded due to extensive production method, energy expenditure and generation of toxic by-products which causes significant risks to the human health and environment. Hence, there is a growing requirement to search substitute, non-expensive, reliable, biocompatible and environmental friendly methods for development of nanoparticles. The nanoparticles synthesis by microorganisms has gained significant interest due to their potential to synthesize nanoparticles in various sizes, shape and composition with different physico-chemical properties. Microbes can be widely applied for nanoparticles production due to easy handling and processing, requirement of low-cost medium such as agro-wastes, simple scaling up, economic viability with the ability of adsorbing and reducing metal ions into nanoparticles through metabolic processes. Biogenic synthesis of nanoparticles offers clean, non-toxic, environmentally benign and sustainable approach in which renewable materials can be used for metal reduction and nanoparticle stabilization. Nanomaterials synthesized through microbes can be used as a pollution abatement tool as they also contain multiple functional groups that can easily target pollutants for efficient bioremediation and promotes environmental cleanup. The objective of the present review is to highlight the significance of micro-organisms like bacteria, actinomycetes, filamentous fungi, yeast, algae and viruses for nanoparticles synthesis and advantages of microbial approaches for elimination of heavy metals, dyes and wastewater treatment.

Bimetallic AgPd/UiO-66 Hybrid Catalysts for Propylene Glycol Oxidation into Lactic Acid

Different methods (the wetness impregnation of Ag and Pd precursors dissolved in water or acetonitrile solution, and the double solvent impregnation technique) were employed to immobilize Ag–Pd nanoparticles (NPs) into the pores of the microporous zirconium-based metal-organic framework known as UiO-66. The obtained materials were characterized by using nitrogen adsorption-desorption at −196 °C, powder X-ray diffraction, UV-Vis diffusion reflectance spectroscopy, and transition electron microscopy measurements. Special attention was paid to the acid and redox properties of the obtained materials, which were studied by using temperature-programmed desorption of ammonia (TPD-NH₃) and temperature-programmed reduction (TPR-H₂) methods. The use of a drying procedure prior to reduction was found to result in metallic NPs which, most likely, formed on the external surface and were larger than corresponding voids of the metal-organic framework. The formation of Ag–Pd alloy or monometallic Ag and Pd depended on the nature of both metal precursors and the impregnation solvent used. Catalytic activity of the AgPd/UiO-66 materials in propylene glycol oxidation was found to be a result of synergistic interaction between the components in AgPd alloyed NPs immobilized in the pore space and on the external surface of UiO-66. The key factor for consistent transformation of propylene glycol into lactic acid was the proximity between redox and acid-base species.

Facile and Rapid Preparation of Ag@ZIF-8 for Carboxylation of Terminal Alkynes with CO2 in Mild Conditions

Metal-organic frameworks (MOFs) are promising hosts for catalytic active sites due to their adjustable porosity and framework chemistry. Strategies to improve synergistic effects between the installed sites and the parent MOF are highly desired. Herein, a facile and rapid method for the preparation of xAg@ZIF-8 materials was reported. The materials were systematically characterized and used as catalysts for carboxylation of terminal alkynes via direct insertion of CO₂ to the C(sp)-H bond (CTA_CO2). It was found that the integrity of the ZIF-8 structure could be retained upon Ag loading, but short-range crystalline ordering was modified. Two types Ag species could be installed, namely, highly dispersed Ag(I) in the backbone (Ag^HD) and aggregated Ag(0) nanoparticles on the outer surface (Ag^NP). The Ag^NP sites are highly effective for the activation of terminal alkynes due to its high accessibility, while the Ag^HD-modified ZIF-8 framework worked as a CO₂ reservoir with enhanced affinity. Combination of these factors translated to high activity in the CTA_CO2 process, the measured turnover frequency and time yield are among the highest among most heterogeneous catalysts.

Biosynthesis of Metal Nanoparticles via Microbial Enzymes: A Mechanistic Approach

During the last decade, metal nanoparticles (MtNPs) have gained immense popularity due to their characteristic physicochemical properties, as well as containing antimicrobial, anti-cancer, catalyzing, optical, electronic and magnetic properties. Primarily, these MtNPs have been synthesized through different physical and chemical methods. However, these conventional methods have various drawbacks, such as high energy consumption, high cost and the involvement of toxic chemical substances. Microbial flora has provided an alternative platform for the biological synthesis of MtNPs in an eco-friendly and cost effective way. In this article we have focused on various microorganisms used for the synthesis of different MtNPs. We also have elaborated on the intracellular and extracellular mechanisms of MtNP synthesis in microorganisms, and have highlighted their advantages along with their challenges. Moreover, due to several advantages over chemically synthesized nanoparticles, the microbial MtNPs, with their exclusive and dynamic characteristics, can be used in different sectors like the agriculture, medicine, cosmetics and biotechnology industries in the near future.