Recent progress in the optical detection of pathogenic bacteria based on noble metal nanoparticles

Ultra-efficient amplification-free biosensor based on electric field and crowding agent-promoted hybridization for the detection of pathogenic bacteria

Pathogenic bacteria represent a significant threat to public health and the global economy due to their high infectiousness and lethality. Consequently, the rapid and accurate identification of these bacteria remains a major challenge. Electrochemical amplification-free detection methods have shown several advantages, including rapidity, simplicity and high sensitivity. However, these methods also possess certain drawbacks, such as the inefficient solid-phase hybridization of long-chain nucleic acids on the electrode surface, it is challenging to directly detect long-chain nucleic acids. In response, we have established a novel sensor platform for efficient and rapid detection of long chain nucleic acids based on the principle of HRP signal amplification. This platform incorporates macromolecular crowding agents and electric field assistance to enhance pathogenic bacteria detection efficiency in clinical samples without amplification. The detection process begins by introducing the target into a strand displacement reaction system containing a crowding agent. The crowding effect of the crowding agent is such that the long chain target rapidly replaces the biotinylated probe. Subsequently, an electric field is applied to the surface of the screen-printed electrodes for rapid hybridization, which has been modified with a capture probe. This assay is straightforward and expeditious, reducing hybridization time from 150 min to 90 s. The sensor platform showed a detection linear range of 102-107 CFU mL-1 with the limit of detection of 10 CFU mL-1 within 25min. This platform showcases the significant potential for on-site detection of pathogenic bacteria in clinical settings and is expected to be integrated into existing diagnostic equipment.

Surface-enhanced Raman scattering based on noble metal nanoassemblies for detecting harmful substances in food

Residues of harmful substances in food can severely damage human health. The content of these substances in food is generally low, making detection difficult. Surface-enhanced Raman scattering (SERS), based on noble metal nanomaterials, mainly gold (Au) and silver (Ag), has exhibited excellent capabilities for trace detection of various substances. Noble metal nanoassemblies, in particular, have extraordinary flexibility and tunable optical properties, which cannot be offered by single nanoparticles (NPs). These nanoassemblies, with their various morphologies synthesized using NPs through artificially induced self-assembly or template-driven preparation, can significantly enhance the local electric field and create "hot spots" due to the gaps between adjacent NPs. Consequently, the SERS properties of NPs become more prominent, leading to improved performance in the trace detection of various substances and detection limits that are considerably lower than the current relevant standards. Noble metal nanoassemblies show promising potential in ensuring food safety. This review discusses the synthesis methods and SERS properties of noble metal nanoassemblies and then concentrates on their application in detecting biotoxins, drug residues, illegal additives, and heavy metals. The study provides valuable references for further research into the application of nanoassemblies in food safety detection.

High-throughput fluorescence sensing array based on tetraphenylethylene derivatives for detecting and distinguishing pathogenic microbes

Infections induced by pathogenic microorganisms will bring negative effects such as diseases that damage health and result in heavy economic burden. Therefore, it is very important to detect and identify the pathogens in time. Moreover, traditional clinical diagnosis or food testing often faces the problem of dealing with a large number of samples. Here, we designed a high-throughput fluorescent sensor array based on the different binding ability of five tetraphenylethylene derivatives (TPEs) with various side chains to different kinds of pathogenic microbes, which is used to detect and distinguish various species, so as to realize rapid mass diagnosis, and hopefully provide guidance for further determination of microbial infections and clinical treatment.

Programmable and ultra-efficient Argonaute protein-mediated nucleic acid tests: A review

With the attributes of high sensitivity, single-base resolution, multiplex detection capability, and programmability upon nucleic acid recognition, Argonaute (Ago)-based biosensing assays are increasingly recognized as one of the most promising tools for precise identification and quantification of target analytes. Employed as highly specific sequence recognition elements of these robust diagnostic methods, Agos are revolutionizing how nucleic acid targets are detected. A systematic and comprehensive summary of this emerging and rapid-advancing technology is necessary to give play to the potential of Ago-based biosensing assays. The structure and function of Agos were briefly overviewed at the beginning of the work, followed by a review of the recent advancements in employing Agos sensing for detecting various targets with a comprehensive analysis such as viruses, tumor biomarkers, pathogens, mycoplasma, and parasite. The significance and benefits of these platforms were then deliberated. In addition, the authors shared subjective viewpoints on the existing challenges and offered relevant guidance for the future progress of Agos assays. Finally, the future research outlook regarding Ago-based sensing in this field was also outlined. As such, this review is expected to offer valuable information and fresh perspectives for a broader group of researchers.

Using gold-based nanomaterials for fighting pathogenic bacteria: from detection to therapy

Owing to the unique quantum size effect and surface effect, gold-based nanomaterials (GNMs) are promising for pathogen detection and broad-spectrum antimicrobial activity. This review summarizes recent research on GNMs as sensors for detecting pathogens and as tools for their elimination. Firstly, the need for pathogen detection is briefly introduced with an overview of the physicochemical properties of gold nanomaterials. And then strategies for the application of GNMs in pathogen detection are discussed. Colorimetric, fluorescence, surface-enhanced Raman scattering (SERS) techniques, dark-field microscopy detection and electrochemical methods can enable efficient, sensitive, and specific pathogen detection. The third section describes the antimicrobial applications of GNMs. They can be used for antimicrobial agent delivery and photothermal conversion and can act synergistically with photosensitizers to achieve the precise killing of pathogens. In addition, GNMs are promising for integrated pathogen detection and treatment; for example, combinations of colorimetric or SERS detection with photothermal sterilization have been demonstrated. Finally, future outlooks for the applications of GNMs in pathogen detection and treatment are summarized.

Gold nanoparticles-based biosensors: pioneering solutions for bacterial and viral pathogen detection-a comprehensive review

Gold Nanoparticles (AuNPs) have gained significant attention in biosensor development due to their unique physical, chemical, and optical properties. When incorporated into biosensors, AuNPs offer several advantages, including a high surface area-to-volume ratio, excellent biocompatibility, ease of functionalization, and tunable optical properties. These properties make them ideal for the detection of various biomolecules, including proteins, nucleic acids, and bacterial and viral biomarkers. Traditional methods for detecting bacteria and viruses, such as RT-PCR and ELISA, often suffer from complexities, time consumption, and labor intensiveness. Consequently, researchers are continuously exploring novel devices to address these limitations and effectively detect a diverse array of infectious pathogenic microorganisms. In light of these challenges, nanotechnology has been instrumental in refining the architecture and performance of biosensors. By leveraging advancements in nanomaterials and strategies of biosensor fabrication the sensitivity and specificity of biosensors can be enhanced, enabling more precise detection of pathogenic bacteria and viruses. This review explores the versatility of AuNPs in detecting a variety of biomolecules, including proteins, nucleic acids, and bacterial and viral biomarkers. Furthermore, it evaluates recent advancements in AuNPs-based biosensors for the detection of pathogens, utilizing techniques such as optical biosensors, lateral flow immunoassays, colorimetric immunosensors, electrochemical biosensors, and fluorescence nanobiosensors. Additionally, the study discusses the existing challenges in the field and proposes future directions to improve AuNPs-based biosensors, with a focus on enhancing sensitivity, selectivity, and their utility in clinical and diagnostic applications.

Spectroscopic and antibacterial activities of cobalt and nickel nanoparticles: a comparative analysis

This study aimed to compare the spectroscopy, morphological, electrocatalytic properties, and antibacterial activities of cobalt nanoparticles (CoNPs) with nickel nanoparticles (NiNPs). Cobalt nanoparticles and NiNPs were prepared via a chemical reduction approach and characterized utilizing transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), and X-ray diffraction (XRD) techniques. The result from XRD and TEM analysis revealed that the synthesized nanoparticles exhibit face-centered cubic with smooth spherical shape, having average particles size of 12 nm (NiNPs) and 18 nm (CoNPs). The electrochemical properties of the nanoparticles were examined via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. The CV results showed that GCE-Ni (35.6 μA) has a higher current response compared to GCE-Co (10.5 μA). The EIS analysis revealed that GCE-Ni (1.39 KΩ) has faster electron transport capability compared to GCE-Co (2.99 KΩ) as indicated in their Rct values. The power density of the synthesized nanoparticles was obtained from their "knee" frequency (f°) values, with GCE-Ni (3.16 Hz) having higher f° values compared to GCE-Co (2.00 Hz). The antibacterial activity of the nanoparticles was evaluated against multidrug-resistant Escherichia coli O157, Escherichia coli O177, Salmonella enterica, Staphylococcus aureus, and Vibrio cholerae. The result from the antibacterial study revealed that at low concentrations both CoNPs and NiNPs have significant antibacterial activities against E. coli O157, E. coli O177, S. enterica, S. aureus, and V. cholerae. NiNPs showed better antibacterial activities at low concentrations of 61.5, 61.5, 125, 61.5, and 125 µg/mL compared to CoNPs with minimum inhibitory concentrations of 125, 125, 250, 61.5, and 125 µg/mL against E. coli O157, E. coli O177, S. enterica, S. aureus, and V. cholerae, respectively. These promising antibacterial activities emphasize the potential of CoNPs and NiNPs as effective antibacterial agents, which could aid in the development of novel antibacterial medicines.

Unravelling the Antimicrobial, Antibiofilm, Suppressing Fibronectin Binding Protein A (fnba) and cna Virulence Genes, Anti-Inflammatory and Antioxidant Potential of Biosynthesized Solanum lycopersicum Silver Nanoparticles

Background and Objectives: Urinary tract infections [UTIs] are considered the third most known risk of infection in human health around the world. There is increasing appreciation for the pathogenicity of Gram-positive and Gram-negative strains in UTIs, aside from fungal infection, as they have numerous virulence factors. Materials and Methods: In this study, fifty urine samples were collected from patients suffering from UTI. Among the isolates of UTI microbes, six isolates were described as MDR isolates after an antibiotic susceptibility test carried out using ten different antibiotics. An alternative treatment for microbial elimination involved the use of biosynthesized silver nanoparticles (AgNPs) derived from Solanum lycopersicum [S. cumin]. Results: The sizes and shapes of AgNPs were characterized through TEM imaging, which showed spherical particles in a size range of 35-80 nm, of which the average size was 53 nm. Additionally, the silver nanoparticles (AgNPs) demonstrated inhibitory activity against Staphylococcus aureus (OR648079), exhibiting a 31 mm zone of inhibition at a minimum inhibitory concentration (MIC) of 4 mg/mL and a minimum bactericidal concentration (MBC) of 8 mg/mL. This was followed by Aspergillus niger (OR648075), which showed a 30 mm inhibition zone at an MIC of 16 mg/mL and a minimum fungicidal concentration (MFC) of 32 mg/mL. Then, Enterococcus faecalis (OR648078), Klebsiella pneumoniae (OR648081), and Acinetobacter baumannii (OR648080) each displayed a 29 mm zone of inhibition at an MIC of 8 mg/mL and an MBC of 16 mg/mL. The least inhibition was observed against Candida auris (OR648076), with a 25 mm inhibition zone at an MIC of 16 mg/mL and an MFC of 32 mg/mL. Furthermore, AgNPs at different concentrations removed DPPH and H2O2 at an IC50 value of 13.54 μg/mL. Also, AgNPs at 3 mg/mL showed remarkable DNA fragmentation in all bacterial strains except Enterococcus faecalis. The phytochemical analysis showed the presence of different active organic components in the plant extract, which concluded that rutin was 88.3 mg/g, garlic acid was 70.4 mg/g, and tannic acid was 23.7 mg/g. Finally, AgNPs concentrations in the range of 3-6 mg/mL showed decreased expression of two of the fundamental genes necessary for biofilm formation within Staphylococcus aureus, fnbA (6 folds), and Cna (12.5 folds) when compared with the RecA gene, which decreased by one-fold when compared with the control sample. These two genes were submitted with NCBI accession numbers [OR682119] and [OR682118], respectively. Conclusions: The findings from this study indicate that biosynthesized AgNPs from Solanum lycopersicum exhibit promising antimicrobial and antioxidant properties against UTI pathogens, including strains resistant to multiple antibiotics. This suggests their potential as an effective alternative treatment for UTIs. Further research is warranted to fully understand the mechanisms of action and to explore the therapeutic applications of these nanoparticles in combating UTIs.

Anti-galvanic reaction induced interfacial engineering to reconstruct ternary colloid satellite platform for exceptionally high-performance redox-responsive sensor

The anti-galvanic reaction (AGR), which is a classic galvanic reaction (GR) with an opposite effect, is a unique phenomenon associated with the quantum size effect. This reaction involves the interaction between metal ions and nanoclusters, offering opportunities to create well-defined nanomaterials and diverse reductive behavior. In hence, in our work, we utilize the AGR to generate gold (Au), silver (Ag), and copper (Cu) satellite nanoclusters which have superior electromagnetic properties for Surface-enhanced Raman spectroscopy (SERS) sensor. As the AGR process, weak oxidant Cu2+ is selected to etched matrix Au@Ag NPs, reduced to Cu(0) or Cu(1) and generated the ultrasmall metal nanoparticles (Ag). To facilitate the AGR, we introduce the nucleophilic thiol 4-mercaptopyridine (4-Mpy) to bridge the metal ions or ultrasmall metal nanoparticles to reconstruct the satellite nanoclusters. These experimental displays that the AGR based biosensors has highly sensitivity for reductive molecule glucose. The liner ranges from 1 mmol/L to 1 nmol/L and alongs with a correlation coefficient and detection limit (LOD) of 0.999 and 0.14 nmol/L. Moreover, the AGR based biosensors exhibits remarkable stability and high repeatability with RSD 1.3 %. The food samples are tested to further investigate the accuracy and reliability of the method, which provides a novel and effective SERS method for the reduction molecules detection.

Nanomaterial-based biosensors for the detection of foodborne bacteria: a review

Ensuring food safety is a critical concern for the development and well-being of humanity, as foodborne illnesses caused by foodborne bacteria have increasingly become a major public health concern worldwide. Traditional food safety monitoring systems are expensive and time-consuming, relying heavily on specialized equipment and operations. Therefore, there is an urgent need to develop low-cost, user-friendly and highly sensitive biosensors for detecting foodborne bacteria. In recent years, the combination of nanomaterials with optical biosensors has provided a prospective future platform for the detection of foodborne bacteria. By harnessing the unique properties of nanomaterials, such as their high surface area-to-volume ratio and exceptional sensitivity, in tandem with the precision of optical biosensing techniques, a new prospect has opened up for the rapid and accurate identification of potential bacterial contaminants in food. This review focuses on recent advances and new trends of nanomaterial-based biosensors for the detection of foodborne pathogens, which mainly include noble metal nanoparticles (NMPs), metal organic frameworks (MOFs), graphene nanomaterials, quantum dot (QD) nanomaterials, upconversion fluorescent nanomaterials (UCNPs) and carbon dots (CDs). Additionally, we summarized the research progress of color indicators, nanozymes, natural enzyme vectors and fluorescent dye biosensors, focusing on the advantages and disadvantages of nanomaterial-based biosensors and their development prospects. This review provides an outlook on future technological directions and potential applications to help identify the most promising areas of development in this field.

Recent Advances in Optical Sensing for the Detection of Microbial Contaminants

Microbial contaminants are responsible for several infectious diseases, and they have been introduced as important potential food- and water-borne risk factors. They become a global burden due to their health and safety threats. In addition, their tendency to undergo mutations that result in antimicrobial resistance makes them difficult to treat. In this respect, rapid and reliable detection of microbial contaminants carries great significance, and this research area is explored as a rich subject within a dynamic state. Optical sensing serving as analytical devices enables simple usage, low-cost, rapid, and sensitive detection with the advantage of their miniaturization. From the point of view of microbial contaminants, on-site detection plays a crucial role, and portable, easy-applicable, and effective point-of-care (POC) devices offer high specificity and sensitivity. They serve as advanced on-site detection tools and are pioneers in next-generation sensing platforms. In this review, recent trends and advances in optical sensing to detect microbial contaminants were mainly discussed. The most innovative and popular optical sensing approaches were highlighted, and different optical sensing methodologies were explained by emphasizing their advantages and limitations. Consequently, the challenges and future perspectives were considered.

Characterization, catalytic, and recyclability studies of nano-sized spherical palladium particles synthesized using aqueous poly-extract (turmeric, neem, and tulasi)

Green synthesis of noble metal nanoparticles (NPs) has gained immense significance compared to other metal ions owing to their unique properties. Among them, palladium 'Pd' has been in the spotlight for its stable and superior catalytic activity. This work focuses on the synthesis of Pd NPs using the combined aqueous extract (poly-extract) of turmeric (rhizome), neem (leaves), and tulasi (leaves). The bio-synthesized Pd NPs were characterized to study its physicochemical and morphological features using several analytical techniques. Role of Pd NPs as nano-catalysts in the degradation of dyes (1 mg/2 mL stock solution) was evaluated in the presence of a strong reducing agent (sodium borohydride; SBH). In the presence of Pd NPs and SBH, maximum reduction of methylene blue (MB), methyl orange (MO), and rhodamine-B (Rh-B) dyes was observed under 20nullmin (96.55 ± 2.11%), 36nullmin (96.96 ± 2.24%), and 27nullmin (98.12 ± 1.33%), with degradation rate of 0.1789 ± 0.0273 min^-1, 0.0926 ± 0.0102 min^-1, and 0.1557 ± 0.0200 min^-1, respectively. In combination of dyes (MB + MO + Rh-B), maximum degradation was observed under 50nullmin (95.49 ± 2.56%) with degradation rate of 0.0694 ± 0.0087 min^-1. It was observed that degradation was following pseudo-first order reaction kinetics. Furthermore, Pd NPs showed good recyclability up to cycle 5 (72.88 ± 2.32%), cycle 9 (69.11 ± 2.19%) and cycle 6 (66.21 ± 2.72%) for MB, MO and Rh-B dyes, respectively. Whereas, up to cycle 4 (74.67 ± 0.66%) during combination of dyes. As Pd NPs showed good recyclability, they can be used for several cycles thus influencing the overall economics of the process.

A universal approach for sensitive and rapid detection of different pathogenic bacteria based on aptasensor-assisted SERS technique

An assembled-aptasensor based on Fe₃O₄@Au@Ag nanocomposites grafting onto the gold foil was prepared, which can be developed into a universal approach for sensitive and rapid detection of various pathogenic bacteria, such as Escherichia coli (E. coli), Salmonella typhimurium (S. typhimurium), Staphylococcus aureus (S. aureus), Listeria monocytogenes (L. monocytogenes), Pseudomonas aeruginosa (P. aeruginosa), and Shigella flexneri (S. flexneri). Firstly, the gold foil paper was modified with thiolated capture probe and SERS tag in proportion, and at the same time, the specific thiolated aptamer probe for corresponding pathogenic bacteria was fixed with Fe₃O₄@Au@Ag nanocomposites. An obvious Raman signal can be subsequently increased about 10⁶ times by the external electromagnetic field enhancement at the "hot spots" caused by the hybridization of aptamer and capture probe. But in the presence of target pathogenic bacteria, Raman intensity will decrease as Fe₃O₄@Au@Ag nanocomposites are dissociated from gold foil. Thus, all of the concentrations of the six kinds of pathogenic bacteria both in PBS and liquorice extract showed an obvious negative linear correlation with the Raman intensity of SERS tag in the range of 10-10⁷ CFU/mL with detection limits were all lower than 10 CFU/mL. And there was no significant difference between our method and the plate counting method. Besides, the assembled-aptasensor had superior specific recognition ability even in the mixed interfering bacteria. Our study showed that this assembled-aptasensor had good specific detection ability to a variety of foodborne pathogens based on magnetic field-assisted SERS technique, which can be used for rapid and sensitive detection of a variety of pathogens in complex substrates.

Synthesis and characterization of Se doped Fe3O4 nanoparticles for catalytic and biological properties

In this study, Se-doped Fe₃O₄ with antibacterial properties was synthesized using by a coprecipitation method. The chemistry and morphology of the Se doped Fe₃O₄ nanocomposite were characterized by energy-dispersive X-ray spectroscopy, field-emission scanning electron microscopy, X-ray diffraction, vibrating sample magnetometry, and Brunauer-Emmett-Teller spectroscopy. The antibacterial activity of the Fe₃O₄/Se nanocomposite was examined against G⁺ (Gram-positive) and G^- (Gram-negative) bacteria, in the order Staphylococcus aureus, Staphylococcus saprophyticus, Pseudomonas aeruginosa, Klebsiella pneumonia, and Escherichia coli, which are the most harmful and dangerous bacteria. Fe₃O₄/Se, as a heterogeneous catalyst, was successfully applied to the synthesis of pyrazolopyridine and its derivatives via a one-pot four-component reaction of ethyl acetoacetate, hydrazine hydrate, ammonium acetate, and various aromatic aldehydes. Fe₃O₄/Se was easily separated from the bacteria-containing solution using a magnet. Its admissible magnetic properties, crystalline structure, antibacterial activity, mild reaction conditions, and green synthesis are specific features that have led to the recommendation of the use of Fe₃O₄/Se in the water treatment field and medical applications. Direct Se doping of Fe₃O₄ was successfully realized without additional complicated procedures.

Recent Advances in Colorimetric Sensors Based on Gold Nanoparticles for Pathogen Detection

Infectious pathogens cause severe threats to public health due to their frightening infectivity and lethal capacity. Rapid and accurate detection of pathogens is of great significance for preventing their infection. Gold nanoparticles have drawn considerable attention in colorimetric biosensing during the past decades due to their unique physicochemical properties. Colorimetric diagnosis platforms based on functionalized AuNPs are emerging as a promising pathogen-analysis technique with the merits of high sensitivity, low-cost, and easy operation. This review summarizes the recent development in this field. We first introduce the significance of detecting pathogens and the characteristics of gold nanoparticles. Four types of colorimetric strategies, including the application of indirect target-mediated aggregation, chromogenic substrate-mediated catalytic activity, point-of-care testing (POCT) devices, and machine learning-assisted colorimetric sensor arrays, are systematically introduced. In particular, three biomolecule-functionalized AuNP-based colorimetric sensors are described in detail. Finally, we conclude by presenting our subjective views on the present challenges and some appropriate suggestions for future research directions of colorimetric sensors.

Rapid Detection of Lipopolysaccharide and Whole Cells of Francisella tularensis Based on Agglutination of Antibody-Coated Gold Nanoparticles and Colorimetric Registration

The paper presents development and characterization of a new bioanalytical test system for rapid detection of lipopolysaccharide (LPS) and whole cells of Francisella tularensis, a causative agent of tularemia, in water samples. Gold nanoparticles (AuNPs) coated by the obtained anti-LPS monoclonal antibodies were used for the assay. Their contact with antigen in tested samples leads to aggregation with a shift of absorption spectra from red to blue. Photometric measurements at 530 nm indicated the analyte presence. Three preparations of AuNPs with different diameters were compared, and the AuNPs having average diameter of 34 nm were found to be optimal. The assay is implemented in 20 min and is characterized by detection limits equal to 40 ng/mL for LPS and 3 × 10⁴ CFU/mL for whole cells of F. tularensis. Thus, the proposed simple one-step assay integrates sensitivity comparable with other immunoassay of microorganisms and rapidity. Selectivity of the assay for different strains of F. tularensis was tested and the possibility to choose its variants with the use of different antibodies to distinguish virulent and non-virulent strains or to detect both kinds of F. tularensis was found. The test system has been successfully implemented to reveal the analyte in natural and tap water samples without the loss of sensitivity.

Escherichia coli Enumeration in a Capillary-Driven Microfluidic Chip with SERS

Pathogen detection is still a challenging issue for public health, especially in food products. A selective preconcentration step is also necessary if the target pathogen concentration is very low or if the sample volume is limited in the analysis. Plate counting (24-48 h) methods should be replaced by novel biosensor systems as an alternative reliable pathogen detection technique. The usage of a capillary-driven microfluidic chip is an alternative method for pathogen detection, with the combination of surface-enhanced Raman scattering (SERS) measurements. Here, we constructed microchambers with capillary microchannels to provide nanoparticle-pathogen transportation from one chamber to the other. Escherichia coli (E. coli) was selected as a model pathogen and specific antibody-modified magnetic nanoparticles (MNPs) as a capture probe in a complex milk matrix. MNPs that captured E. coli were transferred in a capillary-driven microfluidic chip consisting of four chambers, and 4-aminothiophenol (4-ATP)-labelled gold nanorods (Au NRs) were used as the Raman probe in the capillary-driven microfluidic chip. The MNPs provided immunomagnetic (IMS) separation and preconcentration of analytes from the sample matrix and then, 4-ATP-labelled Au NRs provided an SERS response by forming sandwich immunoassay structures in the last chamber of the capillary-driven microfluidic chip. The developed SERS-based method could detect 101-107 cfu/mL of E. coli with the total analysis time of less than 60 min. Selectivity of the developed method was also tested by using Salmonella enteritidis (S. enteritidis) and Staphylococcus aureus (S. aureus) as analytes, and very weak signals were observed.

A New Strategy for Microbial Taxonomic Identification through Micro-Biosynthetic Gold Nanoparticles and Machine Learning

Microorganisms can serve as biological factories for the synthesis of inorganic nanomaterials that can become useful as nanocatalysts, energy-harvesting-storage components, antibacterial agents, and biomedical materials. Herein, the development of biosynthesis of inorganic nanomaterials into a simple, stable, and accurate strategy for distinguishing microorganisms from multiple classification levels (i.e., kingdom, order, genus, and species) without gene amplification, biochemical testing, or target recognition is reported. Gold nanoparticles (AuNPs) biosynthesized by different microorganisms differ in color of the solution, and their features can be characterized, including the particle size, the surface plasmon resonance (SPR) spectrum, and the surface potential. The inter-relation between the features of micro-biosynthetic AuNPs and the classification of microorganisms are exploited at different levels through machine learning to establish a taxonomic model. This model agrees well with traditional classification methods that offers a new strategy for microbial taxonomic identification. The underlying mechanism of this strategy is related to the biomolecules produced by different microorganisms including glucose, glutathione, and nicotinamide adenine dinucleotide phosphate-dependent reductase that regulate the features of micro-biosynthetic AuNPs. This work broadens the application of biosynthesis of inorganic materials through micro-biosynthetic AuNPs and machine learning, which holds great promise as a tool for biomedical research.

Metallic Nanoparticles in the Food Sector: A Mini-Review

Nanomaterials, and in particular metallic nanoparticles (MNPs), have significantly contributed to the production of healthier, safer, and higher-quality foods and food packaging with special properties, such as greater mechanical strength, improved gas barrier capacity, increased water repellency and ability to inhibit microbial contamination, ensuring higher quality and longer product shelf life. MNPs can also be incorporated into chemical and biological sensors, enabling the design of fast and sensitive monitoring devices to assess food quality, from freshness to detection of allergens, food-borne pathogens or toxins. This review summarizes recent developments in the use of MNPs in the field of food science and technology. Additionally, a brief overview of MNP synthesis and characterization techniques is provided, as well as of the toxicity, biosafety and regulatory issues of MNPs in the agricultural, feed and food sectors.