The use of gold nanoparticles in diagnostics and detection

Freeze-Dryable, Stable, and Click-Reactive Nanoparticles Composed of Cello-oligosaccharides for Biomolecular Sensing

Nanoparticles have been widely used as platforms for biomolecular sensing because of their high specific surface area and attractive properties depending on their constituents and structures. Nevertheless, it remains challenging to develop nanoparticulate sensing platforms that are easily storable without aggregation and conjugatable with various ligands in a simple manner. Herein, we demonstrate that nanoparticulate assemblies of cello-oligosaccharides with terminal azido groups are promising candidates. Azidated cello-oligosaccharides can be readily synthesized via the enzyme-catalyzed oligomerization reaction. This study characterized the assembled structures of azidated cello-oligosaccharides produced during the enzymatic synthesis and revealed that the terminal azidated cello-oligosaccharides formed rectangular nanosheet-shaped lamellar crystals. The azido groups located on the nanosheet surfaces were successfully exploited for antigen conjugation via the click chemistry. The resultant antigen-conjugated nanosheets allowed for the quantitative and specific detection of a corresponding antibody, even in 10% serum, owing to the antifouling properties of cello-oligosaccharide assemblies against proteins. It was found that the functionalized nanosheets were redispersible in water after freeze-drying. This remarkable characteristic is attributed to the well-hydrated saccharide residues on the nanosheet surfaces. Moreover, the antibody detection capability did not decline after the thermal treatment of the functionalized nanosheets in a freeze-dried state. Our findings contribute to developing convenient nanoparticulate biomolecular sensing platforms.

A review on gold nanoparticles as an innovative therapeutic cue in bone tissue engineering: Prospects and future clinical applications

Bone damage is a complex orthopedic problem primarily caused by trauma, cancer, or bacterial infection of bone tissue. Clinical care management for bone damage remains a significant clinical challenge and there is a growing need for more advanced bone therapy options. Nanotechnology has been widely explored in the field of orthopedic therapy for the treatment of a severe bone disease. Among nanomaterials, gold nanoparticles (GNPs) along with other biomaterials are emerging as a new paradigm for treatment with excellent potential for bone tissue engineering and regenerative medicine applications. In recent years, a great deal of research has focused on demonstrating the potential for GNPs to provide for enhancement of osteogenesis, reduction of osteoclastogenesis/osteomyelitis, and treatment of bone cancer. This review details the latest understandings in regards to GNPs based therapeutic systems, mechanisms, and the applications of GNPs against various bone disorders. The present review aims to summarize i) the mechanisms of GNPs in bone tissue remodeling, ii) preparation methods of GNPs, and iii) functionalization of GNPs and its decoration on biomaterials as a delivery vehicle in a specific bone tissue engineering for future clinical application.

Acoustic Levitation Synthesis of Ultrahigh-Density Spherical Nucleic Acid Architectures for Specific SERS Analysis

Controllably regulating the electrostatic bilayer of nanogold colloids is a significant premise for synthesizing spherical nucleic acid (SNA) and building ordered plasmonic architectures. We develop a facile acoustic levitation reactor to universally synthesize SNAs with an ultra-high density of DNA strands, which is even higher than those of various state-of-the-art methods. Results reveal a new mechanism of DNA grafting via acoustic wave that can reconfigure the ligands on colloidal surfaces. The acoustic levitation reactor enables substrate-free three-dimentional (3D) spatial assembly of SNAs with controllable interparticle nanogaps through regulating DNA lengths. This kind of architecture may overcome the plasmonic enhancement limits by blocking electron tunneling and breaking electrostatic shielding in dried aggregations. Finite element simulations support the architecture with 3D spatial plasmonic hotspot matrix, and its ultrahigh surface-enhanced Raman scattering (SERS) capability is evidenced by in situ untargeted tracking of biomolecular events during photothermal stimulation (PTS)-induced cell death process. For biomarker diagnosis, the conjugation of adenosine triphosphate (ATP) aptamer onto SNAs enables in situ targeted tracking of ATP during PTS-induced cell death process. Particularly, the CD71 receptor and integrin α3β1 protein on PL45 cell membrance could be well distinguished by label-free SERS fingerprints when using specific XQ-2d and DML-7 aptamers, respectively, to synthesize SNA architectures. Our current acoustic levitation reactor offers a new method for synthesizing SNAs and enables both targeted and untargeted SERS analysis for tracking molecular events in living systems. It promises great potentials in biochemical synthesis and sensing in future.

Ultrasensitive Detection Strategy of Norovirus Based on a Dual Enhancement Strategy: CRISPR-Responsive Self-Assembled SNA and Isothermal Amplification

Spherical nucleic acids (SNAs) have been used to construct various nanobiosensors with gold nanoparticles (AuNPs) as nuclei. The SNAs play a critical role in biosensing due to their various physical and chemical properties, programmability, and specificity recognition ability. In this study, CRISPR-responsive self-assembled spherical nucleic acid (CRISPR-rsSNA) detection probes were constructed by conjugating fluorescein-labeled probes to the surface of AuNPs to improve the sensing performance. Also, the mechanism of ssDNA and the role of different fluorescent groups in the self-assembly process of CRISPR-rsSNA were explored. Then, CRISPR-rsSNA and reverse transcription-recombinase polymerase amplification (RT-RPA) were combined to develop an ultrasensitive fluorescence-detection strategy for norovirus. In the presence of the virus, the target RNA sequence of the virus was transformed and amplified by RT-RPA. The resulting dsDNA activated the trans-cleavage activity of CRISPR cas12a, resulting in disintegrating the outer nucleic acid structure of the CRISPR-rsSNA at a diffusible rate, which released reporter molecules. Norovirus was quantitated by fluorescence detection. This strategy facilitated the detection of the norovirus at the attomolar level. An RT-RPA kit for norovirus detected would be developed based on this method. The proposed method would be used for the detection of different viruses just by changing the target RNA and crRNA of the CRISPR cas12a system which provided a foundation for high-throughput detection of various substances.

Probing Interactions between Chiral Plasmonic Nanoparticles and Biomolecules

Chiral plasmonic nanoparticles (and their assemblies) interact with biomolecules in a variety of different ways, resulting in distinct optical signatures when probed by circular dichroism spectroscopy. These systems show promise for biosensing applications and offer several advantages over achiral plasmonic systems. Arguably the most notable advantage is that chiral nanoparticles can differentiate between molecular enantiomers and can, therefore, act as sensors for enantiomeric purity. Furthermore, chiral nanoparticles can couple more effectively to chiral biomolecules in biological systems if they have a matching handedness, improving their effectiveness as biomedical agents. In this article, we review the different types of interactions that occur between chiral plasmonic nanoparticle systems and biomolecules, and discuss how circular dichroism spectroscopy can probe these interactions and inform how to optimize systems for biosensing and biomedical applications.

CRISPR/Cas-Based Diagnostics in Agricultural Applications

Pests and disease-causing pathogens frequently impede agricultural production. An early and efficient diagnostic tool is crucial for effective disease management. Clustered regularly interspaced short palindromic repeats (CRISPR) and the CRISPR-associated protein (Cas) have recently been harnessed to develop diagnostic tools. The CRISPR/Cas system, composed of the Cas endonuclease and guide RNA, enables precise identification and cleavage of the target nucleic acids. The inherent sensitivity, high specificity, and rapid assay time of the CRISPR/Cas system make it an effective alternative for diagnosing plant pathogens and identifying genetically modified crops. Furthermore, its potential for multiplexing and suitability for point-of-care testing at the field level provide advantages over traditional diagnostic systems such as RT-PCR, LAMP, and NGS. In this review, we discuss the recent developments in CRISPR/Cas based diagnostics and their implications in various agricultural applications. We have also emphasized the major challenges with possible solutions and provided insights into future perspectives and potential applications of the CRISPR/Cas system in agriculture.

Gold Nanoparticles-Based Colorimetric Assays for Environmental Monitoring and Food Safety Evaluation

Recent years have witnessed an exponential increase in the research on gold nanoparticles (AuNPs)-based colorimetric sensors to revolutionize point-of-use sensing devices. Hence, this review is compiled focused on current progress in the design and performance parameters of AuNPs-based sensors. The review begins with the characteristics of AuNPs, followed by a brief explanation of synthesis and functionalization methods. Then, the mechanisms of AuNPs-based sensors are comprehensively explained in two broad categories based on the surface plasmon resonance (SPR) characteristics of AuNPs and their peroxidase-like catalytic properties (nanozyme). SPR-based colorimetric sensors further categorize into aggregation, anti-aggregation, etching, growth-mediated, and accumulation-based methods depending on their sensing mechanisms. On the other hand, peroxidase activity-based colorimetric sensors are divided into two methods based on the expression or inhibition of peroxidase-like activity. Next, the analytes in environmental and food samples are classified as inorganic, organic, and biological pollutants, and recent progress in detection of these analytes are reviewed in detail. Finally, conclusions are provided, and future directions are highlighted. Improving the sensitivity, reproducibility, multiplexing capabilities, and cost-effectiveness for colorimetric detection of various analytes in environment and food matrices will have significant impact on fast testing of hazardous substances, hence reducing the pollution load in environment as well as rendering food contamination to ensure food safety.

Rapid detection of HPV16/18 based on a CRISPR-Cas13a/Cas12a dual-channel system

PURPOSE

cervical cancer is the leading cause of cancer deaths in women in the developing world, with high-risk HPV16 and HPV18 accounting for approximately 70% of all cervical cancers. Early detection of HPV, especially high-risk HPV types, is essential to prevent disease progression.

METHODS

in this study, we established a highly sensitive and specific nucleic acid assay based on a CRISPR-Cas13a/Cas12a dual-channel system combined with multiplex RAA for rapid detection and typing of HPV16/18, which provides a new idea for cervical cancer screening. To meet the application of field testing, we designed a portable fluorescence imaging assay that can judge the test results directly with the naked eye or through cell phone imaging.

RESULTS

the lower limit of detection for both HPV16 and HPV18 based on the CRISPR-Cas12a/Cas13a dual-channel assay was 10⁰ copies per μL. The dual-channel assay was validated with 55 clinical samples, showing 97.06% sensitivity, 100% specificity, 100% positive predictive value, and 96.55% negative predictive value. The results of the portable fluorescence imaging assay were fully comparable to those of the real-time fluorescent RAA-based CRISPR-Cas12a/Cas13a dual-channel assay.

CONCLUSIONS

this developed portable dual gene assay platform may provide new technical support for cervical cancer screening in resource-limited settings.

Development and Application of an SPR Nanobiosensor Based on AuNPs for the Detection of SARS-CoV-2 on Food Surfaces

A new transmission route of SARS-CoV-2 through food was recently considered by the World Health Organization (WHO), and, given the pandemic scenario, the search for fast, sensitive, and low-cost methods is necessary. Biosensors have become a viable alternative for large-scale testing because they overcome the limitations of standard techniques. Herein, we investigated the ability of gold spherical nanoparticles (AuNPs) functionalized with oligonucleotides to detect SARS-CoV-2 and demonstrated their potential to be used as plasmonic nanobiosensors. The loop-mediated isothermal amplification (LAMP) technique was used to amplify the viral genetic material from the raw virus-containing solution without any preparation. The detection of virus presence or absence was performed by ultraviolet-visible (UV-Vis) absorption spectroscopy, by monitoring the absorption band of the surface plasmonic resonance (SPR) of the AuNPs. The displacement of the peak by 525 nm from the functionalized AuNPs indicated the absence of the virus (particular region of gold). On the other hand, the region ~300 nm indicated the presence of the virus when RNA bound to the functionalized AuNPs. The nanobiosensor system was designed to detect a region of the N gene in a dynamic concentration range from 0.1 to 50 × 10³ ng·mL^-1 with a limit of detection (LOD) of 1 ng·mL^-1 (2.7 × 10³ copy per µL), indicating excellent sensitivity. The nanobiosensor was applied to detect the SARS-CoV-2 virus on the surfaces of vegetables and showed 100% accuracy compared to the standard quantitative reverse transcription polymerase chain reaction (RT-qPCR) technique. Therefore, the nanobiosensor is sensitive, selective, and simple, providing a viable alternative for the rapid detection of SARS-CoV-2 in ready-to-eat vegetables.

Nanomaterial and interface advances in immunoassay biosensors

Biosensors have been used for a remarkable array of applications, including infectious diseases, environmental monitoring, cancer diagnosis, food safety, and numerous others. In particular, the global COVID-19 pandemic has exposed a need for rapid tests, so the type of biosensor that has gained considerable interest recently are immunoassays, which are used for rapid diagnostics. The performance of paper-based lateral flow and dipstick immunoassays is influenced by the physical properties of the nanoparticles (NPs), NP-antibody conjugates, and paper substrate. Many materials innovations have enhanced diagnostics by increasing sensitivity or enabling unique readouts. However, negative side effects can arise at the interface between the biological sample and biomolecules and the NP or paper substrate, such as non-specific adsorption and protein denaturation. In this Perspective, we discuss the immunoassay components and highlight chemistry and materials innovations that can improve sensitivity. We also explore the range of bio-interface issues that can present challenges for immunoassays.

A systematic review of the advancement on colorimetric nanobiosensors for SARS-CoV-2 detection

The current pandemic of the acute severe respiratory syndrome coronavirus 2 (SARS-CoV-2) killed about 6.4 million and infected more than 600 million individuals by august of 2022, and researchers worldwide are searching for fast and selective approaches for this virus detection. Colorimetric biosensors are an excellent alternative because they are sensitive, simple, fast, and low-cost for rapid detection of SARS-CoV-2 compared to standard Enzyme-linked immunosorbent assay (ELISA) and Polymerase Chain Reaction (PCR) techniques. This study systematically searched and reviewed literature data related to colorimetric biosensors in detecting SARS-CoV-2 viruses, recovered from the Scopus (n = 16), Web of Science (n = 19), PubMed (n = 19), and Science Direct (n = 17) databases totalizing n = 71 articles. Data were analyzed for the type of nanomaterial, biorecognition material at the detection limit (LOD), and devices designed for diagnostics. The most applied nanomaterial were gold nanoparticles, in their original form and hybrid in quantum dots and core-shell. In addition, we show high specificity in point-of-care (POC) diagnostic devices as a faster and cheaper alternative for clinical diagnosis. Finally, the highlights of the colorimetric biosensor developed for diagnostic devices applied in swabs, surgical masks, and lateral flow immunoassays were presented.

Microenvironmental Behaviour of Nanotheranostic Systems for Controlled Oxidative Stress and Cancer Treatment

The development of smart, efficient and multifunctional material systems for diseases treatment are imperative to meet current and future health challenges. Nanomaterials with theranostic properties have offered a cost effective and efficient solution for disease treatment, particularly, metal/oxide based nanotheranostic systems already offering therapeutic and imaging capabilities for cancer treatment. Nanoparticles can selectively generate/scavenge ROS through intrinsic or external stimuli to augment/diminish oxidative stress. An efficient treatment requires higher oxidative stress/toxicity in malignant disease, with a minimal level in surrounding normal cells. The size, shape and surface properties of nanoparticles are critical parameters for achieving a theranostic function in the microenvironment. In the last decade, different strategies for the synthesis of biocompatible theranostic nanostructures have been introduced. The exhibition of therapeutics properties such as selective reactive oxygen species (ROS) scavenging, hyperthermia, antibacterial, antiviral, and imaging capabilities such as MRI, CT and fluorescence activity have been reported in a variety of developed nanosystems to combat cancer, neurodegenerative and emerging infectious diseases. In this review article, theranostic in vitro behaviour in relation to the size, shape and synthesis methods of widely researched and developed nanosystems (Au, Ag, MnO_x, iron oxide, maghemite quantum flakes, La₂O_3−x, TaO_x, cerium nanodots, ITO, MgO_1−x) are presented. In particular, ROS-based properties of the nanostructures in the microenvironment for cancer therapy are discussed. The provided overview of the biological behaviour of reported metal-based nanostructures will help to conceptualise novel designs and synthesis strategies for the development of advanced nanotheranostic systems.

Peptide-Induced Fractal Assembly of Silver Nanoparticles for Visual Detection of Disease Biomarkers

We report the peptide-programmed fractal assembly of silver nanoparticles (AgNPs) in a diffusion-limited aggregation (DLA) mode, and this change in morphology generates a significant color change. We show that peptides with specific repetitions of defined amino acids (i.e., arginine, histidine, or phenylalanine) can induce assembly and coalescence of the AgNPs (20 nm) into a hyperbranched structure (AgFSs) (∼2 μm). The dynamic process of this assembly was systematically investigated, and the extinction of the nanostructures can be modulated from 400 to 600 nm by varying the peptide sequences and molar ratio. According to this rationale, two strategies of SARS-CoV-2 detection were investigated. The activity of the main protease (Mpro) involved in SARS-CoV-2 was validated with a peptide substrate that can bridge the AgNPs after the proteolytic cleavage. A sub-nanomolar limit of detection (0.5 nM) and the capacity to distinguish by the naked eye in a wide concentration range (1.25-30 nM) were achieved. Next, a multichannel sensor-array based on multiplex peptides that can visually distinguish SARS-CoV-2 proteases from influenza proteases in doped human samples was investigated.

Importance of the Structural and Physicochemical Properties of Silica Nanoshells in the Photothermal Effect of Silica-Coated Au Nanoparticles Suspensions

In this work, monodisperse silica-coated gold nanoparticles (NPs) were synthesized and used for obtaining aqueous colloidal dispersions with an optimum relationship between colloidal stability and photothermal activity. The idea behind this design was to produce systems with the advantages of the presence of a silica shell (biocompatibility, potential for surface modification, and protecting effect) with a minimal loss of optical and thermal properties. With this aim, the photothermal properties of NPs with silica shells of different thicknesses were analyzed under conditions of high radiation extinction. By using amorphous, gel-like silica coatings, thicknesses higher than 40 nm could be obtained without an important loss of the light absorption capacity of the colloids and with a significant photothermal response even at low NP concentrations. The effects produced by changes in the solvent and in the NP concentration were also analyzed. The results show that the characteristics of the shell control both, the photothermal effect and the optical properties of the colloidal dispersions. As the presence of a silica shell strongly enhances the possibilities of adding cargo molecules or probes, these colloids can be considered of high interest for biomedical therapies, sensing applications, remote actuation, and other technological applications.

Broad-Spectrum Theranostics and Biomedical Application of Functionalized Nanomaterials

Nanotechnology is an important branch of science in therapies known as “nanomedicine” and is the junction of various fields such as material science, chemistry, biology, physics, and optics. Nanomaterials are in the range between 1 and 100 nm in size and provide a large surface area to volume ratio; thus, they can be used for various diseases, including cardiovascular diseases, cancer, bacterial infections, and diabetes. Nanoparticles play a crucial role in therapy as they can enhance the accumulation and release of pharmacological agents, improve targeted delivery and ultimately decrease the intensity of drug side effects. In this review, we discussthe types of nanomaterials that have various biomedical applications. Biomolecules that are often conjugated with nanoparticles are proteins, peptides, DNA, and lipids, which can enhance biocompatibility, stability, and solubility. In this review, we focus on bioconjugation and nanoparticles and also discuss different types of nanoparticles including micelles, liposomes, carbon nanotubes, nanospheres, dendrimers, quantum dots, and metallic nanoparticles and their crucial role in various diseases and clinical applications. Additionally, we review the use of nanomaterials for bio-imaging, drug delivery, biosensing tissue engineering, medical devices, and immunoassays. Understandingthe characteristics and properties of nanoparticles and their interactions with the biological system can help us to develop novel strategies for the treatment, prevention, and diagnosis of many diseases including cancer, pulmonary diseases, etc. In this present review, the importance of various kinds of nanoparticles and their biomedical applications are discussed in much detail.

Fast microwave heating-based one-step synthesis of DNA and RNA modified gold nanoparticles

DNA/RNA-gold nanoparticle (DNA/RNA-AuNP) nanoprobes have been widely employed for nanobiotechnology applications. Here, we discover that both thiolated and non-thiolated DNA/RNA can be efficiently attached to AuNPs to achieve high-stable spherical nucleic acid (SNA) within minutes under a domestic microwave (MW)-assisted heating-dry circumstance. Further studies show that for non-thiolated DNA/RNA the conjugation is poly (T/U) tag dependent. Spectroscopy, test strip hybridization, and loading counting experiments indicate that low-affinity poly (T/U) tag mediates the formation of a standing-up conformation, which is distributed in the outer layer of SNA structure. In further application studies, CRISPR/Cas9-sgRNA (136 bp), SARS-CoV-2 RNA fragment (1278 bp), and rolling circle amplification (RCA) DNA products (over 1000 bp) can be successfully attached on AuNPs, which overcomes the routine methods in long-chain nucleic acid-AuNP conjugation, exhibiting great promise in biosensing and nucleic acids delivery applications. Current heating-dry strategy has improved traditional DNA/RNA-AuNP conjugation methods in simplicity, rapidity, cost, and universality.

Simple methods for attaching polynucleotides to gold nanoparticles are of interest for simplifying conjugation in a range of applications. Here, the authors report a microwave heating-based method for the fast, one-step attachment of a range of thiolated or non-thiolated DNA and RNA to gold nanoparticles.

Nucleic acid amplification-integrated single-molecule fluorescence imaging for in vitro and in vivo biosensing

Single-molecule fluorescence imaging is among the most advanced analytical technologies and has been widely adopted for biosensing due to its distinct advantages of simplicity, rapidity, high sensitivity, low sample consumption, and visualization capability. Recently, a variety of nucleic acid amplification approaches have been developed to provide a straightforward and highly efficient way for amplifying low abundance target signals. The integration of single-molecule fluorescence imaging with nucleic acid amplification has greatly facilitated the construction of various fluorescent biosensors for in vitro and in vivo detection of DNAs, RNAs, enzymes, and live cells with high sensitivity and good selectivity. Herein, we review the advances in the development of fluorescent biosensors by integrating single-molecule fluorescence imaging with nucleic acid amplification based on enzyme (e.g., DNA polymerase, RNA polymerase, exonuclease, and endonuclease)-assisted and enzyme-free (e.g., catalytic hairpin assembly, entropy-driven DNA amplification, ligation chain reaction, and hybridization chain reaction) strategies, and summarize the principles, features, and in vitro and in vivo applications of the emerging biosensors. Moreover, we discuss the remaining challenges and future directions in this area. This review may inspire the development of new signal-amplified single-molecule biosensors and promote their practical applications in fundamental and clinical research.

Advances in Field Detection Based on CRISPR/Cas System

Rapid and accurate diagnostic methods are essential to interrupt outbreaks of infectious diseases such as COVID-19. However, the most commonly used nucleic acid detection method, qPCR or RT-qPCR, takes several hours to complete and requires highly sophisticated equipment. Recently, an emerging nucleic acid detection method based on the CRISPR/Cas system has reduced the reliance on qPCR. It has several important features that make it suitable for on-site POCT (point-of-care testing), including short detection cycles, low cost, high sensitivity, and the ability to be combined with different readout methods. This review briefly introduces the steps of CRISPR/Cas detection and then summarizes the current advances of CRISPR/Cas-based POCT from four steps: nucleic acid extraction, target amplification, CRISPR/Cas-based signal generation, and signal output. Finally, we discuss the advantages and challenges of CRISPR-based POCT and describe the future research perspectives for CRISPR.

Paper-Based Multiplexed Colorimetric Device for the Simultaneous Detection of Salivary Biomarkers

In this study, we describe a monolithic and fully integrated paper-based device for the simultaneous detection of three prognostic biomarkers in saliva. The pattern of the proposed multiplexed device is designed with a central sample deposition zone and three identical arms, each containing a pre-treatment and test zone. Its one-step fabrication is realized by CO₂ laser cutting, providing remarkable parallelization and rapidity (ca. 5 s/device). The colorimetric detection is based on the sensitive and selective target-induced reshaping of plasmonic multibranched gold nanoparticles, which exhibit a clear spectral shift (and blue-to-pink color change) in case of non-physiological concentrations of the three salivary biomarkers. A rapid and multiplexed naked-eye or smartphone-based readout of the colorimetric response is achieved within 10 min. A prototype kit for POCT testing is also reported, providing robustness and easy handling of the device.

Dual-functional gold-iron oxide core-satellite hybrid nanoparticles for sensitivity enhancement in biosensors via nanoplasmonic and preconcentration effects

A common strategy to improve the sensitivity of a biosensor for the detection of a low abundance analyte is to preconcentrate the analyte molecules before detection. A dual-functional gold-iron oxide core-satellite hybrid nanoparticle structure is proposed in this work to overcome the drawbacks of traditional sample pretreatment methods and the methods using non-magnetic nanomaterials for sample pretreatment. The new dual-functional hybrid nanoparticle structure can simultaneously serve as a signal reporter of a biorecognition event and a preconcentrator of a target at an extremely low concentration in a nanoplasmonic biosensor. By utilizing a fiber optic nanogold-linked sorbent assay in the fiber optic particle plasmon resonance (FOPPR) biosensor and an arbitrary DNA sequence as a target, we have demonstrated that the use of the new hybrid nanoparticle structure with magnetic preconcentration improves the limit of detection (LOD) for the DNA by 18 times as compared to the same method without magnetic preconcentration, so that the LOD for detecting the DNA can be as low as 2.6 fM. The new hybrid nanoparticle structure is easy to prepare and its use in the high-sensitivity and low-cost FOPPR biosensor provides vast opportunities in point-of-care applications.

Nanotechnology for Targeted Detection and Removal of Bacteria: Opportunities and Challenges

The emergence of nanotechnology has created unprecedented hopes for addressing several unmet industrial and clinical issues, including the growing threat so-termed "antibiotic resistance" in medicine. Over the last decade, nanotechnologies have demonstrated promising applications in the identification, discrimination, and removal of a wide range of pathogens. Here, recent insights into the field of bacterial nanotechnology are examined that can substantially improve the fundamental understanding of nanoparticle and bacteria interactions. A wide range of developed nanotechnology-based approaches for bacterial detection and removal together with biofilm eradication are summarized. The challenging effects of nanotechnologies on beneficial bacteria in the human body and environment and the mechanisms of bacterial resistance to nanotherapeutics are also reviewed.

A brief review of the essential role of nanovehicles for improving the therapeutic efficacy of pharmacological agents against tumours

Cancer is the leading cause of death globally. There are several differences between cancer cells and normal cells. From all the therapies, chemotherapy is the most prominent therapy to treat cancer. However, the conventional drug delivery that is used to deliver poorly aqueous soluble chemotherapeutic agents has several obstacles such as whole-body distribution, rapid excretion, degradation before reaching the infected site, side effects, etc. Nanoformulation of these aqueous insoluble agents is the emerging delivery system for targeted and increasing solubility. Among all the three methods (physical, chemical and biological) chemical and biological methods are mostly used for the synthesis of nanovehicles (NVs) of different sizes, shapes and dimensions. A passive targeting delivery system in which NVs supports the pharmacological agents (drugs/genes) is a good way for resolving the obstacles with a conventional delivery system. It enhances the therapeutic efficacy of pharmacological agents (drugs/genes). These NVs have several specific characters like small size, large surface area to volume ratio, surface functionalization, etc. However, this delivery is not able to deliver site-specific delivery of drugs. An active targeting delivery system in which pharmacological agents are loaded on NVs to attack directly on cancer cells and tissues is a superior way for delivering the pharmacological agents compared to a passive targeting delivery system. Various targeting ligands have been investigated and applied for targeting the delivery of drugs such as sugar, vitamin, antibodies, protein, peptides, etc. These targeted ligand supports to guide the NVs accumulated directly on the cancer cells with a higher level of cellular internalization compared to passive targeting and conventional delivery system.

Photoluminescence enhancement by controllable aggregation and polymerization of octanuclear gold clusters

Aggregation-induced luminescence behaviors of polynuclear metal clusters are intriguing but still mysterious to date. Herein, we synthesize a series of Au8 clusters with different peripheral ligands to investigate their different supramolecular assembly and distinguishable aggregation-induced luminescent behaviors in solution upon the variation of concentration and solvent polarity. Complex 1a is surrounded by two tetraphenyl ethylene (TPE) moieties, whose dense stacking engenders strong aggregation in solution. Furthermore, the incorporation of the TPE-decorated gold clusters into a polymer backbone promotes molecular restriction within a constrained polymer micelle and thus facilitates efficient emission enhancement of gold clusters. In contrast, the other two gold clusters with small ethynylbenzene and chloride as peripheral ligands exhibit low emission efficiency. The contrastive study showcases how the peripheral ligand arrangements influence assemblies of metal clusters and potentiates such effects in the rational design of cluster-based luminescent materials.

Advances in Clustered, Regularly Interspaced Short Palindromic Repeats (CRISPR)-Based Diagnostic Assays Assisted by Micro/Nanotechnologies

Clustered, regularly interspaced short palindromic repeats (CRISPR)-based diagnoses, derived from gene-editing technology, have been exploited for less than 5 years and are now reaching the stage of precommercial use. CRISPR tools have some notable features, such as recognition at physiological temperature, excellent specificity, and high-efficiency signal amplification capabilities. These characteristics are promising for the development of next-generation diagnostic technologies. In this Perspective, we present a detailed summary of which micro/nanotechnologies play roles in the advancement of CRISPR diagnosis and how they are involved. The use of nanoprobes, nanochips, and nanodevices, microfluidic technology, lateral flow strips, etc. in CRISPR detection systems has led to new opportunities for CRISPR-based diagnosis assay development, such as achieving equipment-free detection, providing more compact detection systems, and improving sensitivity and quantitative capabilities. Although tremendous progress has been made, CRISPR diagnosis has not yet reached its full potential. We discuss upcoming opportunities and improvements and how micro/nanotechnologies will continue to play key roles.

TiO2 Nano-test tubes as a solid visual platform for sensitive Pb2+ ion detection based on a fluorescence resonance energy transfer (FRET) process

A cost-effective, facile, and sensitive fluorescence sensing strategy for Pb²⁺ ion detection has been developed based on the fluorescence resonance energy transfer (FRET) between carbon quantum dots (CQDs) and Au nanoparticles (NPs). Glutathione (GSH)-synthesized CQDs acted as both the fluorescence donor and the sorbent to extract Pb²⁺ ions from the solution via Pb-GSH complexes. Pb²⁺ ions on CQDs reacted with -SH groups on AuNPs to generate sandwich-type Au-PdS-CQDs, leading to a dramatic decrease in the fluorescence of the CQDs. To expand the potential applications of this strategy, we constructed a sensing strategy using self-organized TiO₂ nanotube arrays (TiNTs). The high aspect ratio and transparency for light emitted from the CQDs enabled the TiNTs to serve as a sensitive solid visual platform for the highly selective detection of Pb²⁺ ions with a detection limit as low as 4.1 × 10^-8 mg mL^-1. More importantly, the long observation length combined with a small volume enabled a sample acquisition volume of only 2.1 × 10^-3 μL, which is smaller than the traditional fluorescence analysis in solution and on commercially available test paper, thus endowing this visual platform with the potential for use in single-cell diagnostics.

Multiplexed and amplified chemiluminescence resonance energy transfer (CRET) detection of genes and microRNAs using dye-loaded hemin/G-quadruplex-modified UiO-66 metal-organic framework nanoparticles

Dye-loaded UiO-66 metal-organic framework nanoparticles (NMOFs) modified with catalytic hemin/G-quadruplex DNAzyme labels act as functional hybrid modules for the chemiluminescence resonance energy transfer (CRET) analysis of miRNAs (miRNA-155 or miRNA-21) or genes (p53 or BRCA1). The dye-loaded NMOFs (dye = fluorescein (Fl) or rhodamine 6G (Rh 6G)) are modified with hairpin probes that are engineered to include in their loop domains recognition sequences for the miRNAs or genes, and in their stem regions caged G-quadruplex domains. In the presence of the analytes miRNAs or genes, the hairpin structures are opened, leading, in the presence of hemin, to the self-assembly of hemin/G-quadruplex DNAzyme labels linked to the dye-loaded NMOFs. In the presence of luminol and H2O2, the hemin/G-quadruplex DNAzyme labels catalyze the generation of chemiluminescence that provides radiative energy to stimulate the process of CRET to the dye loaded in the NMOFs, resulting in the luminescence of the loaded dye without external excitation. The resulting CRET signals relate to the concentrations of the miRNAs or the genes and allow the sensitive analysis of miRNAs and genes. In addition, the DNA hairpin-functionalized dye-loaded NMOF sensing modules were further applied to develop amplified miRNA or gene CRET-based sensing platforms. The dye-loaded NMOFs were modified with hairpin probes that include in their loop domain the recognition sequences for miRNA-155 or miRNA-21 or the recognition sequences for the p53 or BRCA1 genes. Subjecting the hairpin-modified NMOFs to the respective miRNAs or genes, in the presence of two hairpins H i and H j that include in their stem regions caged G-quadruplex subunit domains, results in the analyte-triggered opening of the probe hairpin linked to the NMOFs, and the opened hairpin tethers induce the cross-opening of the hairpins H i and H j by the hybridization chain reaction, HCR, resulting in the assembly of G-quadruplex wires tethered to the NMOFs. The binding of hemin to the HCR-generated chains yields hemin/G-quadruplex DNAzyme wires that enhance, in the presence of luminol/H2O2, the CRET processes in the hybrid nanostructures. These amplification platforms lead to the amplified sensing of miRNAs and genes. By mixing the Fl- and Rh 6G-loaded hairpin-functionalized UiO NMOFs, the multiplexed CRET detection of miRNA-155, miRNA-21 and the p53 and BRCA1 genes is demonstrated.

Recent progress in plant-gold nanoparticles fabrication methods and bio-applications

The preparation of gold nanoparticles via green routes applying plant extracts as the reducing agents and stabilizers has received broad interest in the last decades. Plant-gold nanoparticles have been well-developed and applied in biochemical and medical research, but there are still challenges that must be overcome. The main challenges include the construction of chemically-robust plant-gold nanoparticles, the precise design of biomimetic surfaces to fabricate nanozymes with high catalytic activities, and the development of approaches to construct biosensors with high selectivities and sensitivities. The cores and surfaces of plant-gold nanoparticles must be considered, as well as their catalytic activities and biosensing mechanisms. This review highlights the latest achievements in plant-gold nanoparticle preparation, heterogeneous nucleation, and surface functionalization, while also focusing on their optical properties and various biological and catalytic activities. Moreover, their antioxidant and cell apoptosis mechanisms, and biological activities are described. Plant-gold nanoparticles have shown great potential in high-performance analytical assays, high-activity catalysts, effective intracellular imaging, and clinical treatment.

Colorimetric Aptasensor for Testosterone Detection Based on Aggregation of Gold Nanoparticles Induced by Cationic Surfactant

This paper proposes a colorimetric aptasensor for the detection of testosterone (TES) in environmental water, using TES-specific aptamer (apT5) as a sensing probe, gold nanoparticles (AuNPs) as indicator, and hexadecyltrimethylammonium bromide (CTAB) as inducer, respectively. Based on competition between TES and CTAB for apT5, the aptamer can form an aptamer–TES complex, leaving CTAB free to aggregate AuNPs in the presence of TES. Dispersed and aggregated AuNPs have different absorption wavelengths and the signal of absorption intensity is associated with the concentration of TES, so TES can be detected quantitatively based on the signal absorption intensity. This sensitive aptasensor for TES detection has a wide linear range (R=0.998) from 1.91–800nM and a limit of detection (LOD) of 1.91nM. In addition, this aptasensor has high selectivity over some interferents. The method detects TES in tap water samples with recoveries in the range of 98.9–102.6% (RSD ≤ 7.35%). This biosensor presents a good and potential application to rapidly detect TES in actual environmental water samples.

Four-Channel Photothermal Plate Reader for High-Throughput Nanoparticle-Amplified Immunoassay

We enhanced the sample throughput of microplate-based photothermal detection by using a semicylindrical prism to expand a point laser source to a long beam for illuminating multiple wells. Coupled with four epoxy-coated thermocouples in alignment with wells on a 96-well microplate, four parallel immunoassays of C-reaction protein (CRP) with antibody-conjugated gold nanoparticles can be simultaneously performed. The sample throughput is further increased by mounting the Styrofoam-enclosed microplate onto a translational/elevator stage so that immunoassays and thermocouple rinse/drying cycles can be implemented in a programmed fashion. The automated assay with three rinse/drying cycles takes only 34.5 min for four samples or 8.62 min/sample, whereas the manual mode with a single thermocouple and a point light source requires at least 66 min for just one sample. With careful calibration of the energy distribution of the expanded laser beam and controllable immersion of the thermocouples, excellent well-to-well (RSD = 1.3%) and cycle-to-cycle (RSD = 4.0%) reproducibility can be attained. The temperature changes can be correlated with the CRP concentration by the Langmuir isotherm, and the low limit of detection, 0.52 ng/mL or 4.33 pM, is well below the plasma CRP levels of both healthy people (<5 μg/mL) and patients (10-500 μg/mL). The serum CRP concentrations quantified by our plate reader are in excellent agreement with the immunoturbidimetric results, demonstrating that this cost-effective, robust, and high-throughput mode for microplate-based immunoassays is amenable to detecting biomarkers in many clinical samples.

Advanced in developmental organic and inorganic nanomaterial: a review

With the unique properties such as high surface area to volume ratio, stability, inertness, ease of functionalization, as well as novel optical, electrical, and magnetic behaviors, nanomaterials have a wide range of applications in various fields with the common types including nanotubes, dendrimers, quantum dots, and fullerenes. With the aim of providing useful insights to help future development of efficient and commercially viable technology for large-scale production, this review focused on the science and applications of inorganic and organic nanomaterials, emphasizing on their synthesis, processing, characterization, and applications on different fields. The applications of nanomaterials on imaging, cell and gene delivery, biosensor, cancer treatment, therapy, and others were discussed in depth. Last but not least, the future prospects and challenges in nanoscience and nanotechnology were also explored.

The Effects of Gold Nanoparticles on Leydig Cells and Male Reproductive Function in Mice

Background

Gold nanoparticles (AuNPs) have shown great promise in various biomedical applications, but their effects on male reproductive function remain to be ascertained. The aim of this study was to investigate the uptake, cytotoxicity and testosterone production inhibition of AuNPs in mouse Leydig cells, as well as their accumulation in the testes of male mice and their effects on male reproductive function.

Results

AuNPs (5 nm) were able to be internalized into the endosomes/lysosomes of TM3 Leydig cells, induce the formation of autophagosomes, increase the production of reactive oxygen species (ROS), and disrupt the cell cycle in S phase, resulting in concentration-dependent cytotoxicity and DNA damage. Interestingly, AuNPs significantly reduced testosterone production in TM3 cells by inhibiting the expression of 17α-hydroxylase, an important enzyme in androgen synthesis. After repeated intravenous injection, AuNPs gradually accumulated and retained in the testes of male BALB/c mice in a dose-dependent manner. One week after withdrawal, the level of plasma testosterone in the 0.5 mg/kg AuNPs group was significantly reduced compared to that in the PBS control group, accompanied by the decreased expression of 17α-hydroxylase in the testes. In addition, AuNPs treatment significantly increased the rate of epididymal sperm malformation, but without affecting fertility.

Conclusion

Our results suggest that AuNPs can accumulate in the testes and reduce testosterone production in Leydig cells by down-regulating the expression of 17α-hydroxylase, thus affecting the quality of epididymal sperm.

Cooperation of N-Heterocyclic Carbenes on a Gold Surface

Atomically precise tailoring of interface structures is crucial for developing functional materials. We demonstrate an N-heterocyclic carbene (NHC) based molecular tool, which modifies the structure of a gold surface with atomic accuracy by the formation of gold nanorods. After adsorption on the gold surface, individual surface atoms are pulled out by the NHCs, generating single-atom surface defects and mobile NHC-Au species. Atomistic calculations reveal that these molecular "ballbots" can act as assembling tools to dislocate individual surface atoms. The predicted functionality of these carbene-based complexes is confirmed by scanning tunneling microscopy measurements. Cooperative operation of these NHC-Au species induces a step-wise formation of gold nanorods. Consequently, the surface is re-structured by a zipper-type mechanism. Our work presents a foundation to utilize molecular-based nanotools to design surface structures.

Optical detection of di- and triphosphate anions with mixed monolayer-protected gold nanoparticles containing zinc(II)-dipicolylamine complexes

Gold nanoparticles covered with a mixture of ligands of which one type contains solubilizing triethylene glycol residues and the other peripheral zinc(II)–dipicolylamine (DPA) complexes allowed the optical detection of hydrogenphosphate, diphosphate, and triphosphate anions in water/methanol 1:2 (v/v). These anions caused the bright red solutions of the nanoparticles to change their color because of nanoparticle aggregation followed by precipitation, whereas halides or oxoanions such as sulfate, nitrate, or carbonate produced no effect. The sensitivity of phosphate sensing depended on the nature of the anion, with diphosphate and triphosphate inducing visual changes at significantly lower concentrations than hydrogenphosphate. In addition, the sensing sensitivity was also affected by the ratio of the ligands on the nanoparticle surface, decreasing as the number of immobilized zinc(II)–dipicolylamine groups increased. A nanoparticle containing a 9:1 ratio of the solubilizing and the anion-binding ligand showed a color change at diphosphate and triphosphate concentrations as low as 10 μmol/L, for example, and precipitated at slightly higher concentrations. Hydrogenphosphate induced a nanoparticle precipitation only at a concentration of ca. 400 μmol/L, at which the precipitates formed in the presence of diphosphates and triphosphates redissolved. A nanoparticle containing fewer binding sites was more sensitive, while increasing the relative number of zinc(II)–dipicolylamine complexes beyond 25% had a negative impact on the limit of detection and the optical response. Transmission electron microscopy provided evidence that the changes of the nanoparticle properties observed in the presence of the phosphates were due to a nanoparticle crosslinking, consistent with the preferred binding mode of zinc(II)–dipicolylamine complexes with phosphate anions which involves binding of the anion between two metal centers. This work thus provided information on how the behavior of mixed monolayer-protected gold nanoparticles is affected by multivalent interactions, at the same time introducing a method to assess whether certain biologically relevant anions are present in an aqueous solution within a specific concentration range.

Clinical Applications of Visual Plasmonic Colorimetric Sensing

Colorimetric analysis has become of great importance in recent years to improve the operationalization of plasmonic-based biosensors. The unique properties of nanomaterials have enabled the development of a variety of plasmonics applications on the basis of the colorimetric sensing provided by metal nanoparticles. In particular, the extinction of localized surface plasmon resonance (LSPR) in the visible range has permitted the exploitation of LSPR colorimetric-based biosensors as powerful tools for clinical diagnostics and drug monitoring. This review summarizes recent progress in the biochemical monitoring of clinical biomarkers by ultrasensitive plasmonic colorimetric strategies according to the distance- or the morphology/size-dependent sensing modes. The potential of colorimetric nanosensors as point of care devices from the perspective of naked-eye detection is comprehensively discussed for a broad range of analytes including pharmaceuticals, proteins, carbohydrates, nucleic acids, bacteria, and viruses such as Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). The practical suitability of plasmonic-based colorimetric assays for the rapid visual readout in biological samples, considering current challenges and future perspectives, is also reviewed.

The Optical Spectrum of Au2. Angew Chem Int Ed Engl 2020;59:21403-21408. [PMID: 32888257 PMCID: PMC7756737 DOI: 10.1002/anie.202011337]

The electronic structure of the Au₂ ⁺ cation is essential for understanding its catalytic activity. We present the optical spectrum of mass-selected Au₂ ⁺ measured via photodissociation spectroscopy. Two vibrationally resolved band systems are observed in the 290-450 nm range (at ca. 440 and ca. 325 nm), which both exhibit rather irregular structure indicative of strong vibronic and spin-orbit coupling. The experimental spectra are compared to high-level quantum-chemical calculations at the CASSCF-MRCI level including spin-orbit coupling. The results demonstrate that the understanding of the electronic structure of this simple, seemingly H₂ ⁺ -like diatomic molecular ion strictly requires multireference and relativistic treatment including spin-orbit effects. The calculations reveal that multiple electronic states contribute to each respective band system. It is shown that popular DFT methods completely fail to describe the complex vibronic pattern of this fundamental diatomic cation.

Metal-based nanoparticles for bone tissue engineering

Tissue is vital to the organization of multicellular organisms, because it creates the different organs and provides the main scaffold for body shape. The quest for effective methods to allow tissue regeneration and create scaffolds for new tissue growth has intensified in recent years. Tissue engineering has recently used some promising alternatives to existing conventional scaffold materials, many of which have been derived from nanotechnology. One important example of these is metal nanoparticles. The purpose of this review is to cover novel tissue engineering methods, paying special attention to those based on the use of metal-based nanoparticles. The unique physiochemical properties of metal nanoparticles, such as antibacterial effects, shape memory phenomenon, low cytotoxicity, stimulation of the proliferation process, good mechanical and tensile strength, acceptable biocompatibility, significant osteogenic potential, and ability to regulate cell growth pathways, suggest that they can perform as novel types of scaffolds for bone tissue engineering. The basic principles of various nanoparticle-based composites and scaffolds are discussed in this review. The merits and demerits of these particles are critically discussed, and their importance in bone tissue engineering is highlighted.

Rational Design of Functional Peptide-Gold Hybrid Nanomaterials for Molecular Interactions

Gold nanoparticles (AuNPs) have been extensively used for decades in biosensing-related development due to outstanding optical properties. Peptides, as newly realized functional biomolecules, are promising candidates of replacing antibodies, receptors, and substrates for specific molecular interactions. Both peptides and AuNPs are robust and easily synthesized at relatively low cost. Hence, peptide-AuNP-based bio-nano-technological approaches have drawn increasing interest, especially in the field of molecular targeting, cell imaging, drug delivery, and therapy. Many excellent works in these areas have been reported: demonstrating novel ideas, exploring new targets, and facilitating advanced diagnostic and therapeutic technologies. Importantly, some of them also have been employed to address real practical problems, especially in remote and less privileged areas. This contribution focuses on the application of peptide-gold hybrid nanomaterials for various molecular interactions, especially in biosensing/diagnostics and cell targeting/imaging, as well as for the development of highly active antimicrobial/antifouling coating strategies. Rationally designed peptide-gold nanomaterials with functional properties are discussed along with future challenges and opportunities.