Intracellular biosynthesis of PbS quantum dots using Pseudomonas aeruginosa ATCC 27853: evaluation of antibacterial effects and DNA cleavage activities

Microbial Fabrication of Quantum Dots: Mechanism and Applications

More recently, the application of semiconductor nanomaterials called quantum dots (QDs), has gained considerable attention as they possess tunable optoelectronic and physicochemical properties. There are several routes of QDs synthesis some of which include lithography, molecular beam epitaxy, and chemical reduction. However, most of these methods are expensive, labour intensive, and produce toxic by-products. Hence, the biosynthesis of QDs has been extensively researched for addressing the issues. This review elaborates on the biogenic synthesis of cadmium selenide, cadmium telluride, cadmium sulfide, lead sulfide, and zinc sulfide QDs using bacteria, and fungi. Further, we attempt to identify the underlying mechanism and critical parameters that can control the synthesis of QDs. Eventually, their application in detectors, photovoltaics, biodiesel, photocatalysis, infection-control, and bioimaging are discussed. Thus, biogenic QDs have a tremendous scope in future to emerge as next generation nanotheranostics although thorough pharmacokinetic, and pharmacodynamic studies are required.

Exopolymeric substances production by Bacillus cereus KMS3-1 enhanced its biosorption efficiency in removing Cd2+ and Pb2+ in single and binary metal mixtures

The present study investigated the growth, exopolymeric substance (EPS) production, and biosorption efficiency of strain Bacillus cereus KMS3-1 in the Cd²⁺ and Pb²⁺ ions containing single and binary metal-treated broth (50 mg/L). In addition, the interaction of the KMS3-1 strain with Cd²⁺ and Pb²⁺ ions in single and binary metal-treated broths was investigated using SEM-EDS, FTIR, and XRD analyses. The results showed that the biosorption efficiency (%) and EPS production of KMS3-1 biomass in both single and binary metal-treated broths had increased with increasing incubation time and were higher for Pb²⁺ ions than for Cd²⁺ ions. In the single and binary metal-treated broths, the maximum biosorption efficiency of KMS3-1 for Pb²⁺ ions were 70.8% and 46.3%, respectively, while for Cd²⁺ ions, they were 29.3% and 16.8%, respectively, after 72 h. Moreover, the biosorption efficiency of strain KMS3-1 for both metal ions was dependent on its EPS production and peaked at the maximum EPS production. The copious EPS production by KMS3-1 was observed in metal-treated media (50 mg/L), in the following order: Pb²⁺ ions (1925.7 μg/mL) > binary metal mixtures (1286.8 μg/mL) > Cd²⁺ ions (1185.5 μg/mL), > control (1099 μg/mL) after 72 h of incubation. This result indicates that the metal biosorption efficiency of the KMS3-1 strain was enhanced by the increased EPS production in the surrounding metal-treated broth. SEM-EDS and FTIR characterization studies revealed that the KMS3-1 biomass effectively adsorbed Cd²⁺ and Pb²⁺ ions from the medium by interacting with their surface functional groups (hydroxyl, carbonyl, carboxyl, amide, and phosphate). Moreover, the biosorbed Cd²⁺ and Pb²⁺ ions were transformed into CdS and PbS, respectively, by the KMS3-1 biomass. This study suggests that the Bacillus cereus KMS3-1 strain may be a promising candidate for the treatment of metal contamination.

Biosynthesis of Quantum Dots and Their Therapeutic Applications in the Diagnosis and Treatment of Cancer and SARS-CoV-2

Quantum dots (QDs) are semiconductor materials that range from 2 nm to 10 nm. These nanomaterials (NMs) are smaller and have more unique properties compared to conventional nanoparticles (NPs). One of the unique properties of QDs is their special optoelectronic properties, making it possible to apply these NMs in bioimaging. Different size and shape QDs, which are used in various fields such as bioimaging, biosensing, cancer therapy, and drug delivery, have so far been produced by chemical methods. However, chemical synthesis provides expensive routes and causes serious environmental and health issues. Therefore, various biological systems such as bacteria, fungi, yeasts, algae, and plants are considered as potent eco-friendly green nanofactories for the biosynthesis of QDs, which are both economic and environmentally safe. The review aims to provide a descriptive overview of the various microbial agents for the synthesis of QDs and their biomedical applications for the diagnosis and treatment of cancer and SARS-CoV-2.

Microbe-mediated transformation of metal sulfides: Mechanisms and environmental significance

Microorganisms play a key role in the natural circulation of various constituent elements of metal sulfides. Some microorganisms (such as Thiobacillus ferrooxidans) can promote the oxidation of metal sulfides to increase the release of heavy metals. However, other microorganisms (such as Desulfovibrio vulgaris) can transform heavy metals into metal sulfides crystals. Therefore, insight into the metal sulfides transformation mediated by microorganisms is of great significance to environmental protection. In this review, first, we discuss the mechanism and influencing factors of microorganisms transforming heavy metals into metal sulfides crystals in different environments. Then, we explore three microbe-mediated transformation forms of heavy metals to metal sulfides and their environmental applications: (1) transformation to metal sulfides precipitation for metal resource recovery; (2) transformation to metal sulfides nanoparticles (NPs) for pollutant treatment; (3) transformation to "metal sulfides-microbe" biohybrid system for clean energy production and pollutant remediation. Finally, we further provide critical views on the application of microbe-mediated metal sulfides transformation in the environmental field and discuss the need for future research.

Ultrafine multi-metal (Zn, Cd, Pb) sulfide aggregates formation in periodically water-logged organic soil

This study investigates authigenic metal (Zn, Cd, and Pb) sulfides formed in the upper (4-20 cm) layer of severely degraded soil close to ZnPb smelter in CE Europe (southern Poland). The soil layer is circumneutral (pH 6.0-6.8), organic, occasionally water-logged, and contains on average 26,400 mg kg^-1 Zn, 18,800 mg kg^-1 Pb, 1300 mg kg^-1 Cd, and 2500 mg kg^-1 of sulfur. The distribution of the authigenic sulfide mineralization is uneven, showing close association with the remains of vascular plants (Equisetaceae, Carex, and herbs). A combination of focused ion beam (FIB) technology with scanning (SEM) and transmission electron microscopy (TEM) is used to reveal the structure and organization of the metal sulfides at micro- and nanoscale resolution. The sulfides form spheroidal and botryoidal porous aggregates composed of nanocrystalline (<5 nm) ZnCd sulfide solid solution and minor discrete PbS (galena) crystals up to 15 nm. The solid solution exists in a cubic (sphalerite) polytype over a whole Zn/Cd range. An intricate core-shell structure is found to be a characteristic feature of the aggregates in which high-Zn outer layers encapsulate Cd-rich sulfide core. PbS resides between the Cd-rich and Cd poor sulfide within nano sites of increased porosity. The study highlights the importance of nanoscale analyses for the prediction of metal behavior in soils. The sulfide self-organization into complex structures and Cd encapsulation inside high-Zn sulfide indicate the occurrence of a self-sustainable mechanism specific to polluted periodically water-logged soil that limits Cd mobility. However, as the reduced Cd mobility is obtained at the Zn expense, the soil gets Cd enriched relative to Zn over extended periods. Although the study proves PbS crystallization in the soil, the process seems environmentally irrelevant even at high Pb contents, being suppressed by other soil processes (e.g., Pb sorption on organic matter). Our findings are valuable in remediation strategies and the management of contaminated soils rich in organic matter that address the mobility of toxic metals and their transfer into living organisms.

Bioactive Graphene Quantum Dots Based Polymer Composite for Biomedical Applications

Today, nanomedicine seeks to develop new polymer composites to overcome current problems in diagnosing and treating common diseases, especially cancer. To achieve this goal, research on polymer composites has expanded so that, in recent years, interdisciplinary collaborations between scientists have been expanding day by day. The synthesis and applications of bioactive GQD-based polymer composites have been investigated in medicine and biomedicine. Bioactive GQD-based polymer composites have a special role as drug delivery carriers. Bioactive GQDs are one of the newcomers to the list of carbon-based nanomaterials. In addition, the antibacterial and anti-diabetic potentials of bioactive GQDs are already known. Due to their highly specific surface properties, π-π aggregation, and hydrophobic interactions, bioactive GQD-based polymer composites have a high drug loading capacity, and, in case of proper correction, can be used as an excellent option for the release of anticancer drugs, gene carriers, biosensors, bioimaging, antibacterial applications, cell culture, and tissue engineering. In this paper, we summarize recent advances in using bioactive GQD-based polymer composites in drug delivery, gene delivery, thermal therapy, thermodynamic therapy, bioimaging, tissue engineering, bioactive GQD synthesis, and GQD green resuscitation, in addition to examining GQD-based polymer composites.

Group IV nanodots: synthesis, surface engineering and application in bioimaging and biotherapy

Group IV nanodots (NDs) mainly including carbon (C), silicon (Si), germanium (Ge) have aroused much attention as one type of important nanomaterials that are widely studied in optoelectronics, semiconductors, sensors and biomedicine-related fields owing to the low cost of synthesis, good stability, excellent biocompatibility, and some attractive newly emerged properties. In this review, the synthesis, surface engineering and application in bioimaging and biotherapy of group IV NDs are summarized and discussed. The recent progress in the rational synthesis and functionalization, specific therapy-related properties, together with in vivo and in vitro bioimaging are highlighted. Their new applications in biotherapy such as photothermal therapy (PTT) and photodynamic therapy (PDT) are illustrated with respect to C, Si and Ge NDs. The current challenges and future applications of these emerging materials in bioimaging and biotherapy are presented. This review provides readers with a distinct perspective of the group IV NDs nanomaterials for synthesis and surface engineering, and newly emerging properties related to applications in biomedicine.