Optical Multiplexed Bioassays for Improved Biomedical Diagnostics

Simultaneous targeting and monitoring of free antigen and in-situ membrane antigen in prostate cancer cells via an aggregation-induced emission-based bifunctional probe

The precise clinical diagnosis of prostate cancer still presents inherent challenges, and usually a monitoring of multiple biomarkers is required. In this study, a new aggregation-induced emission (AIE)-based bifunctional strategy was developed for the simultaneous detection of prostate cancer-specific in situ membrane antigens (PSMA) and free antigens (PSA). First, a bifunctional fluorescent probe with double sensing sites (a PSA-specific sensing site and a PSMA-targeted ligand) was constructed. In the presence of PSA, it specifically binds to the PSA-specific sensing site of the probe, resulting in the restoration of the fluorescence signal, enabling linear sensing of PSA. For the detection of PSMA, the PSMA-targeted ligand modified on the probe can specifically recognize PSMA, inducing the aggregation of the AIE material and resulting in an enhanced fluorescence signal. Moreover, a liposome-based artificial cell was developed to simulate the real prostate cancer cell, and it was used to investigate the feasibility of monitoring the two types of antigens. Utilizing this bifunctional fluorescent strategy, a dual-analysis of free serum antigen biomarker of PSA and in-situ membrane antigen of PSMA was achieved. The assay exhibited a wide linearity range for PSA detection from 0.0001 to 0.1 μg/mL, with a low limit of detection (LOD) of 6.18 pg/mL. For PSMA, the obtained LOD is 8.79 pg/mL, with a linearity range from 0.0001 to 0.1 μg/mL. This strategy allows us to simultaneously assess the levels of two types of biomarkers in living human prostatic cancer cells, providing a highly accurate and selective tool for early screening and monitoring of prostatic cancer.

Modular probe integrating with quantum dots based versatile platform for sensitive and label-free biomarker detection

Multiplexed analysis of biomarkers in a single sample tube is essential for accurate diagnosis and therapy of diseases. However, the existing detection platforms suffer from many drawbacks, such as low specificity, limited applicable sceneries, and complicated operation. Hence, it is highly important to develop a versatile biomarker detection platform that can be used for disease diagnosis and pathophysiological research. In this study, we provide a versatile method for detecting biomarkers using dual-loop probes and quantum dots (QDs). This approach utilizes a dual-loop probe that consists of a recognition module for identifying specific targets, a template recognition module for initiating subsequent chain replacement cycles, and a signal module for facilitating the fixation of QDs on the 96-well plate. The lower limit of detection for miRNA-21 is determined to be at the aM level. Furthermore, this design may be easily expanded to simultaneously detect several targets, such as miRNA and C-reactive protein. The experimental results demonstrated the successful construction of the versatile biomarkers detection platform, and indicated that the sensitive and versatile platform has significant potential in the areas of bio-sensing, clinical diagnostics, and environmental sample analysis.

Ultrasensitive Dual ELONA/SERS-RPA Multiplex Diagnosis of Antimicrobial Resistance

Antimicrobial resistance (AMR) is a significant global health threat concern, necessitating healthcare practitioners to accurately prescribe the most effective antimicrobial agents with correct doses to combat resistant infections. This is necessary to improve the therapeutic outcomes for patients and prevent further increase in AMR. Consequently, there is an urgent need to implement rapid and sensitive clinical diagnostic methods to identify resistant pathogenic strains and monitor the efficacy of antimicrobials. In this study, we report a novel proof-of-concept magnetic scaffold-recombinase polymerase amplification (RPA) technique, coupled with an enzyme-linked oligonucleotide assay (ELONA) and surface-enhanced Raman scattering (SERS) detection, aimed at selectively amplifying and detecting the DNA signature of three resistant carbapenemase genes, VIM, KPC, and IMP. To achieve this, streptavidin-coated magnetic beads were functionalized with biotin-modified forward primers. RPA was conducted on the surface of the beads, resulting in an immobilized duplex amplicon featuring a single overhang tail specific to each gene. These tails were subsequently hybridized with recognition HRP probes conjugated to a complementary single-stranded oligonucleotide and detected colorimetrically. Additionally, they underwent hybridization with similar selective SERS probes and were measured using a handheld Raman spectrometer. The resulting quantification limits were at subpicomolar level for both assays, allowing the potential for early diagnosis. Moreover, we demonstrated the platform capability to conduct a multiplex RPA-SERS detection of the three genes in a single tube. Compared to similar approaches like PCR, RPA offers advantages of speed, affordability, and isothermal operation at 37 °C, eliminating the need for a thermal cycler. The whole assay was completed within <2 h. Therefore, this novel magnetic scaffold ELONA/SERS-RPA platform, for DNA detection, demonstrated excellent capability for the rapid monitoring of AMR in point-of-care applications, in terms of sensitivity, portability, and speed of analysis.

Ultrasimple size encoded microfluidic chip for rapid simultaneous multiplex detection of DNA sequences

Simultaneous multiplexed analysis can provide comprehensive information for disease diagnosis. However, the current multiplex methods rely on sophisticated barcode technology, which hinders its wider application. In this study, an ultrasimple size encoding method is proposed for multiplex detection using a wedge-shaped microfluidic chip. Driving by negative pressure, microparticles are naturally arranged in distinct stripes based on their sizes within the chip. This size encoding method demonstrates a high level of precision, allowing for accuracy in distinguishing 3-5 sizes of microparticles with a remarkable accuracy rate of up to 99%, even the microparticles with a size difference as small as 0.5 μm. The entire size encoding process is completed in less than 5 min, making it ultrasimple, reliable, and easy to operate. To evaluate the function of this size encoding microfluidic chip, three commonly co-infectious viruses' nucleic acid sequences (including complementary DNA sequences of HIV and HCV, and DNA sequence of HBV) are employed for multiplex detection. Results indicate that all three DNA sequences can be sensitively detected without any cross-interference. This size-encoding microfluidic chip-based multiplex detection method is simple, rapid, and high-resolution, its successful application in serum samples renders it highly promising for potential clinical promotion.

Persistent Luminescence Lifetime-Based Near-Infrared Nanoplatform via Deep Learning for High-Fidelity Biosensing of Hypochlorite

In light of deep tissue penetration and ultralow background, near-infrared (NIR) persistent luminescence (PersL) bioprobes have become powerful tools for bioapplications. However, the inhomogeneous signal attenuation may significantly limit its application for precise biosensing owing to tissue absorption and scattering. In this work, a PersL lifetime-based nanoplatform via deep learning was proposed for high-fidelity bioimaging and biosensing in vivo. The persistent luminescence imaging network (PLI-Net), which consisted of a 3D-deep convolutional neural network (3D-CNN) and the PersL imaging system, was logically constructed to accurately extract the lifetime feature from the profile of PersL intensity-based decay images. Significantly, the NIR PersL nanomaterials represented by Zn1+xGa2-2xSnxO4: 0.4 % Cr (ZGSO) were precisely adjusted over their lifetime, enabling the PersL lifetime-based imaging with high-contrast signals. Inspired by the adjustable and reliable PersL lifetime imaging of ZGSO NPs, a proof-of-concept PersL nanoplatform was further developed and showed exceptional analytical performance for hypochlorite detection via a luminescence resonance energy transfer process. Remarkably, on the merits of the dependable and anti-interference PersL lifetimes, this PersL lifetime-based nanoprobe provided highly sensitive and accurate imaging of both endogenous and exogenous hypochlorite. This breakthrough opened up a new way for the development of high-fidelity biosensing in complex matrix systems.

Encoding fluorescence intensity with tetrahedron DNA nanostructure based FRET effect for bio-detection

Biocoding technology constructed by readable tags with distinct signatures is a brand-new bioanalysis method to realize multiplexed identification and bio-information decoding. In this study, a novel fluorescence intensity coding technology termed Tetra-FICT was reported based on tetrahedron DNA nanostructure (TDN) carrier and Főrster Resonance Energy Transfer (FRET) effect. By modulating numbers and distances of Cy3 and Cy5 at four vertexes of TDN, different fluorescence intensities of twenty-six samples were produced at ∼565.0 nm (FICy3) and ∼665.0 nm (FICy5) by detecting fluorescence spectra. By developing an error correction mechanism, eleven codes were established based on divided intensity ranges of the final FICy3 together with FICy5 (Final-FICy3&FICy5). These resulting codes were used to construct barcode probes, with three miRNA biomarkers (miRNA-210, miRNA-199a and miRNA-21) as cases for multiplexed bio-assay. The high specificity and sensitivity were also demonstrated for the detection of miRNA-210. Overall, the proposed Tetra-FICT enriched the toolbox of fluorescence coding, which could be applied to multiplexing biomarkers detection.

Luminescence Lifetime-Based Sensing Platform Based on Cyclometalated Iridium(III) Complexes for the Detection of Perfluorooctanoic Acid in Aqueous Samples

Luminescence lifetimes are an attractive analytical method for detection due to its high sensitivity and stability. Iridium probes exhibit luminescence with long excited-state lifetimes, which are sensitive to the local environment. Perfluorooctanoic acid (PFOA) is listed as a chemical of high concern regarding its toxicity and is classified as a "forever chemical". In addition to strict limits on the presence of PFOA in drinking water, environmental contamination from industrial effluent or chemical spills requires rapid, simple, accurate, and cost-effective analysis in order to aid containment. Herein, we report the fabrication and function of a novel and facile luminescence sensor for PFOA based on iridium modified on gold surfaces. These surfaces were modified with lipophilic iridium complexes bearing alkyl chains, namely, IrC6 and IrC12, and Zonyl-FSA surfactant. Upon addition of PFOA, the modified surfaces IrC6-FSA@Au and IrC12-FSA @Au show the largest change in the red luminescence signal with changes in the luminescence lifetime that allow monitoring of PFOA concentrations in aqueous solutions. The platform was tested for the measurement of PFOA in aqueous samples spiked with known concentrations of PFOA and demonstrated the capacity to determine PFOA at concentrations >100 μg/L (240 nM).

Silver Nanocluster-Tagged Electrochemiluminescence Immunoassay with a Sole and Narrow Triggering Potential Window

The commercialized electrochemiluminescence (ECL) immunoassay is carried out by holding luminophore Ru(bpy)32+ at a given potential. Designing an electrochemiluminophore with a narrow triggering potential window is strongly anticipated to decrease the electrochemical cross-talk and improve the flux of the commercialized ECL immunoassay in a potential-resolved way. Herein, L-penicillamine-capped silver nanoclusters (LPA-AgNCs) are facilely synthesized and utilized as tags to perform the ECL immunoassay with a sole and narrow triggering potential window of 0.24 V by employing hydrazine (N2H4) as a coreactant. The maximum ECL emission of the LPA-AgNCs/N2H4 system is located ca. +1.27 V. Upon immobilizing LPA-AgNCs onto the electrode surface via forming a sandwich immunocomplex, the ECL of LPA-AgNCs/N2H4 can be utilized to sensitively and selectively determine human carcinoembryonic antigen from 0.5 to 1000 pg/mL with a low limit of detection of 0.1 pg/mL (S/N = 3). This work might open a way to screen electrochemiluminophores for the multiple ECL immunoassay in a potential-resolved way.

Nanocrystals for Deep-Tissue In Vivo Luminescence Imaging in the Near-Infrared Region

In vivo imaging technologies have emerged as a powerful tool for both fundamental research and clinical practice. In particular, luminescence imaging in the tissue-transparent near-infrared (NIR, 700-1700 nm) region offers tremendous potential for visualizing biological architectures and pathophysiological events in living subjects with deep tissue penetration and high imaging contrast owing to the reduced light-tissue interactions of absorption, scattering, and autofluorescence. The distinctive quantum effects of nanocrystals have been harnessed to achieve exceptional photophysical properties, establishing them as a promising category of luminescent probes. In this comprehensive review, the interactions between light and biological tissues, as well as the advantages of NIR light for in vivo luminescence imaging, are initially elaborated. Subsequently, we focus on achieving deep tissue penetration and improved imaging contrast by optimizing the performance of nanocrystal fluorophores. The ingenious design strategies of NIR nanocrystal probes are discussed, along with their respective biomedical applications in versatile in vivo luminescence imaging modalities. Finally, thought-provoking reflections on the challenges and prospects for future clinical translation of nanocrystal-based in vivo luminescence imaging in the NIR region are wisely provided.

Quality Control of Mass-Encoded Nanodevices by Compartmented DNA Origami Frames for Precision Information Coding and Logic Mapping

Encoded nanostructures afford an ideal platform carrying multi-channel signal components for multiplexed assay and information security. However, with the demand on exclusivity and reproducibility of coding signals, precise control on the structure and composition of nanomaterials featuring fully distinguishable signals remains challenging. By using the multiplexing capability of mass spectrometry (MS) and spatial addressability of DNA origami nanostructures, we herein propose a quality control methodology for constructing mass-encoded nanodevices (namely MNTs-TDOFs) in the scaffold of compartmented tetrahedral DNA origami frames (TDOFs), in which the arrangement and stoichiometry of four types of mass nanotags (MNTs) can be finely regulated and customized to generate characteristic MS patterns. The programmability of combinatorial MNTs and orthogonality of individual compartments allows further evolution of MNTs-TDOFs to static tagging agents and dynamic nanoprobes for labeling and sensing of multiple targets. More importantly, structure control at single TDOF level ensures the constancy of prescribed MS outputs, by which a high-capacity coding system was established for secure information encryption and decryption. In addition to the multiplexed outputs in parallel, the nanodevices could also map logic circuits with interconnected complexity and logic events of c-Met recognition and dimerization on cell surface for signaling regulation by MS interrogation.

An Extended NIR-II Superior Imaging Window from 1500 to 1900 nm for High-Resolution In Vivo Multiplexed Imaging Based on Lanthanide Nanocrystals

High-resolution in vivo optical multiplexing in second near-infrared window (NIR-II, 1000-1700 nm) is vital to biomedical research. Presently, limited by bio-tissue scattering, only luminescent probes located at NIR-IIb (1500-1700 nm) window can provide high-resolution in vivo multiplexed imaging. However, the number of available luminescent probes in this narrow NIR-IIb region is limited, which hampers the available multiplexed channels of in vivo imaging. To overcome the above challenges, through theoretical simulation we expanded the conventional NIR-IIb window to NIR-II long-wavelength (NIR-II-L, 1500-1900 nm) window on the basis of photon-scattering and water-absorption. We developed a series of novel lanthanide luminescent nanoprobes with emission wavelengths from 1852 nm to 2842 nm. NIR-II-L nanoprobes enabled high-resolution in vivo dynamic multiplexed imaging on blood vessels and intestines, and provided multi-channels imaging on lymph tubes, tumors and intestines. The proposed NIR-II-L probes without mutual interference are powerful tools for high-contrast in vivo multiplexed detection, which holds promise for revealing physiological process in living body.

Multifunctional Nanoplatform for NIR-II Imaging-Guided Synergistic Oncotherapy

Tumors are a major public health issue of concern to humans, seriously threatening the safety of people's lives and property. With the increasing demand for early and accurate diagnosis and efficient treatment of tumors, noninvasive optical imaging (including fluorescence imaging and photoacoustic imaging) and tumor synergistic therapies (phototherapy synergistic with chemotherapy, phototherapy synergistic with immunotherapy, etc.) have received increasing attention. In particular, light in the near-infrared second region (NIR-II) has triggered great research interest due to its penetration depth, minimal tissue autofluorescence, and reduced tissue absorption and scattering. Nanomaterials with many advantages, such as high brightness, great photostability, tunable photophysical properties, and excellent biosafety offer unlimited possibilities and are being investigated for NIR-II tumor imaging-guided synergistic oncotherapy. In recent years, many researchers have tried various approaches to investigate nanomaterials, including gold nanomaterials, two-dimensional materials, metal sulfide oxides, polymers, carbon nanomaterials, NIR-II dyes, and other nanomaterials for tumor diagnostic and therapeutic integrated nanoplatform construction. In this paper, the application of multifunctional nanomaterials in tumor NIR-II imaging and collaborative therapy in the past three years is briefly reviewed, and the current research status is summarized and prospected, with a view to contributing to future tumor therapy.

Deep Insight of Design, Mechanism, and Cancer Theranostic Strategy of Nanozymes

Since the discovery of enzyme-like activity of Fe3O4 nanoparticles in 2007, nanozymes are becoming the promising substitutes for natural enzymes due to their advantages of high catalytic activity, low cost, mild reaction conditions, good stability, and suitable for large-scale production. Recently, with the cross fusion of nanomedicine and nanocatalysis, nanozyme-based theranostic strategies attract great attention, since the enzymatic reactions can be triggered in the tumor microenvironment to achieve good curative effect with substrate specificity and low side effects. Thus, various nanozymes have been developed and used for tumor therapy. In this review, more than 270 research articles are discussed systematically to present progress in the past five years. First, the discovery and development of nanozymes are summarized. Second, classification and catalytic mechanism of nanozymes are discussed. Third, activity prediction and rational design of nanozymes are focused by highlighting the methods of density functional theory, machine learning, biomimetic and chemical design. Then, synergistic theranostic strategy of nanozymes are introduced. Finally, current challenges and future prospects of nanozymes used for tumor theranostic are outlined, including selectivity, biosafety, repeatability and stability, in-depth catalytic mechanism, predicting and evaluating activities.

Recent Progress on Fluorescent Probes in Heavy Metal Determinations for Food Safety: A Review

One of the main challenges faced in food safety is the accumulation of toxic heavy metals from environmental sources, which can sequentially endanger human health when they are consumed. It is invaluable to establish a practical assay for the determination of heavy metals for food safety. Among the current detection methods, technology based on fluorescent probes, with the advantages of sensitivity, convenience, accuracy, cost, and reliability, has recently shown pluralistic applications in the food industry, which is significant to ensure food safety. Hence, this review systematically presents the recent progress on novel fluorescent probes in determining heavy metals for food safety over the past five years, according to fluorophores and newly emerging sensing cores, which could contribute to broadening the prospects of fluorescent materials and establishing more practical assays for heavy metal determinations.

Gold Microbeads Enabled Proximity Electrochemiluminescence for Highly Sensitive and Size-Encoded Multiplex Immunoassays

Developing highly sensitive multiplex immunoassays is urgently needed to guide medical research and improve clinical diagnosis. Here, we report the proximity electrochemiluminescence (ECL) generation enabled by gold microbeads (GMBs) for improving the detection sensitivity and multiplexing capacity of ECL immunoassays (ECLIAs). As demonstrated by microscopy and finite element simulation, GMBs can function as spherical ultramicroelectrodes for triggering ECL reactions in solutions. Employing GMBs as solid carriers in the bead-based ECLIA, the electrochemical oxidation of a coreactant can occur at both the GMB surface and the substrate electrode, allowing the coreactant radicals to diffuse only a short distance of ∼100 nm to react with ECL luminophores that are labeled on the GMB surface. The ECL generation via this proximity low oxidation potential (LOP) route results in a 21.7-fold increase in the turnover frequency of ECL generation compared with the non-conductive microbeads that rely exclusively on the conventional LOP route. Moreover, the proximity ECL generation is not restricted by the diffusion distance of short-lived coreactant radicals, which enables the simultaneous determination of multiple acute myocardial infarction biomarkers using size-encoded GMB-based multiplex ECLIAs. This work brings new insight into the understanding of ECL mechanisms and may advance the practical use of multiplex ECLIAs.

Dual-potential encoded electrochemiluminescence for multiplexed gene assay with one luminophore as tag

Multiplexed gene assay for simultaneously detecting the multi-targets of nucleic acids is strongly anticipated for the accurate diseases diagnosis and prediction, and all commercial available gene assays for IVD are a kind of single-target assay. Herein, a dual-potential encoded and coreactant-free electrochemiluminescence (ECL) strategy is proposed for the multiplexed gene assay, which can be conveniently carried out by directly oxidizing the same luminescent tag of dual-stabilizers-capped CdTe nanocrystals (NCs). The CdTe NCs linked with sulfhydryl-RNA via Cd-S bond merely exhibits one ECL process around 0.32 V with a narrow triggering-potential-window of 0.35 V, while CdTe NCs linked with amino-RNA via amide linkage solely gives off one ECL process around 0.82 V with a narrow triggering-potential-window of 0.30 V. Multiplexing ECL of both sulfhydryl-RNA-functionalized CdTe NCs and amino-RNA-functionalized CdTe NCs can be utilized to simultaneously detect the open reading frame 1ab (ORF1ab) and the nucleoprotein (N) genes without crosstalk, in which ECL of sulfhydryl-RNA-functionalized CdTe NCs can dynamically determine ORF1ab from 200 aM to 10 fM with a limit of detection (LOD) of 100 aM, while ECL of amino-RNA-functionalized CdTe NCs can linearly detect N gene from 5 fM to 1 pM with a LOD of 2 fM. Post-engineering CdTe NCs with RNA in a labeling-bond engineering way would provide a potential-selective and encoded ECL strategy for multiplexed gene assay with one luminophore.

Aptamers Targeting Membrane Proteins for Sensor and Diagnostic Applications

Many biological processes (physiological or pathological) are relevant to membrane proteins (MPs), which account for almost 30% of the total of human proteins. As such, MPs can serve as predictive molecular biomarkers for disease diagnosis and prognosis. Indeed, cell surface MPs are an important class of attractive targets of the currently prescribed therapeutic drugs and diagnostic molecules used in disease detection. The oligonucleotides known as aptamers can be selected against a particular target with high affinity and selectivity by iterative rounds of in vitro library evolution, known as Systematic Evolution of Ligands by EXponential Enrichment (SELEX). As an alternative to antibodies, aptamers offer unique features like thermal stability, low-cost, reuse, ease of chemical modification, and compatibility with various detection techniques. Particularly, immobilized-aptamer sensing platforms have been under investigation for diagnostics and have demonstrated significant value compared to other analytical techniques. These "aptasensors" can be classified into several types based on their working principle, which are commonly electrochemical, optical, or mass-sensitive. In this review, we review the studies on aptamer-based MP-sensing technologies for diagnostic applications and have included new methodological variations undertaken in recent years.

Ultrasensitive Multiplex Imaging of Cell Surface Proteins via Core-Shell Surface-Enhanced Raman Scattering Nanoprobes

Cell surface proteins, as important components of biological membranes, cover a wide range of important markers of diseases and even cancers. In this regard, precise detection of their expression levels is of crucial importance for both cancer diagnosis and the development of responsive therapeutic strategies. Herein, a size-controlled core-shell Au@ Copper(II) benzene-1,3,5-tricarboxylate (Au@Cu-BTC) nanomaterial was synthesized for specific and simultaneous imaging of multiple protein expression levels on cell membranes. The porous shell of Cu-BTC constructed on Au nanoparticles enabled effective loading of Raman reporter molecules, followed by further modification of the targeting moieties, which equipped the nanoprobe with good specificity and stability. Additionally, given the flexibility of the types of Raman reporter molecules available for loading, the nanoprobes were also demonstrated with good multichannel imaging capabilities. Ultimately, the present strategy of electromagnetic and chemical dual Raman scattering enhancement was successfully applied for the simultaneous detection of varied proteins on cell surfaces with high sensitivity and accuracy. The proposed nanomaterial holds promising applications in biosensing and therapeutic fields, which could not only provide a general strategy for the synthesis of metal-organic framework-based core-shell surface-enhanced Raman scattering nanoprobes but also enable further utilization in multitarget and multichannel cell imaging.

Design and Synthesis of SERS Materials for In Vivo Molecular Imaging and Biosensing

Surface-enhanced Raman scattering (SERS) is a feasible and ultra-sensitive method for biomedical imaging and disease diagnosis. SERS is widely applied to in vivo imaging due to the development of functional nanoparticles encoded by Raman active molecules (SERS nanoprobes) and improvements in instruments. Herein, the recent developments in SERS active materials and their in vivo imaging and biosensing applications are overviewed. Various SERS substrates that have been successfully used for in vivo imaging are described. Then, the applications of SERS imaging in cancer detection and in vivo intraoperative guidance are summarized. The role of highly sensitive SERS biosensors in guiding the detection and prevention of diseases is discussed in detail. Moreover, its role in the identification and resection of microtumors and as a diagnostic and therapeutic platform is also reviewed. Finally, the progress and challenges associated with SERS active materials, equipment, and clinical translation are described. The present evidence suggests that SERS could be applied in clinical practice in the future.

Multiplex Surface-Enhanced Raman Scattering: An Emerging Tool for Multicomponent Detection of Food Contaminants

For survival and quality of human life, the search for better ways to ensure food safety is constant. However, food contaminants still threaten human health throughout the food chain. In particular, food systems are often polluted with multiple contaminants simultaneously, which can cause synergistic effects and greatly increase food toxicity. Therefore, the establishment of multiple food contaminant detection methods is significant in food safety control. The surface-enhanced Raman scattering (SERS) technique has emerged as a potent candidate for the detection of multicomponents simultaneously. The current review focuses on the SERS-based strategies in multicomponent detection, including the combination of chromatography methods, chemometrics, and microfluidic engineering with the SERS technique. Furthermore, recent applications of SERS in the detection of multiple foodborne bacteria, pesticides, veterinary drugs, food adulterants, mycotoxins and polycyclic aromatic hydrocarbons are summarized. Finally, challenges and future prospects for the SERS-based detection of multiple food contaminants are discussed to provide research orientation for further.

Liver-Targeted Near-Infrared Fluorescence/Photoacoustic Dual-Modal Probe for Real-Time Imaging of In Situ Hepatic Inflammation

Early diagnosis of hepatic inflammation is the key to timely treatment and avoid the worsening of liver inflammation. Near-infrared fluorescence (NIRF) probes have high sensitivity but low spatial resolution in lesion imaging, while photoacoustic (PA) imaging has good spatial location information. Therefore, the development of a NIRF/PA dual-modal probe integrated with high sensitivity and spatial location feedback can achieve an accurate early diagnosis of hepatic inflammation. Here, we report an activatable NIRF/PA dual-modal probe (hCy-Tf-CA) for the detection of the superoxide anion (O₂^·-) in early hepatic inflammation. hCy-Tf-CA showed high selectivity and sensitivity for detecting O₂^·- fluctuation in vitro. More importantly, by introducing hepatocyte-targeting cholic acid (CA), the probe successfully achieved accurate in situ imaging of acute inflammatory liver injury (AILI) and autoimmune hepatitis (AIH) in vivo. The introduced CA not only promotes the hepatic targeting accumulation of probes but also improves the performance of low background dual-modal imaging in vivo. Therefore, hCy-Tf-CA provides an effective strategy for significantly improving in situ imaging performance and holds great potential for early, sensitive, and accurate diagnosis of hepatic inflammation.

Transmissible H-aggregated NIR-II fluorophore to the tumor cell membrane for enhanced PTT and synergistic therapy of cancer

Photothermal therapy (PTT) combined with second near-infrared (NIR-II) fluorescence imaging (FI) has received increasing attention owing to its capacity for precise diagnosis and real-time monitoring of the therapeutic effects. It is of great clinical value to study organic small molecular fluorophores with both PTT and NIR-II FI functions. In this work, we report a skillfully fluorescent lipid nanosystem, the RR₉ (RGDRRRRRRRRRC) peptide-coated anionic liposome loaded with organic NIR-II fluorophore IR-1061 and chemotherapeutic drug carboplatin, which is named RRIALP-C4. According to the structural interaction between IR-1061 and phospholipid bilayer demonstrated by molecular dynamics simulations, IR-1061 is rationally designed to possess the H-aggregated state versus the free state, thus rendering RRIALP-C4 with the activated dual-channel integrated function of intravital NIR-II FI and NIR-I PTT. Functionalization of RRIALP-C4 with RR₉ peptide endows the specifically targeting capacity for α_vβ₃-overexpressed tumor cells and, more importantly, allows IR-1061 to transfer the H-aggregated state from liposomes to the tumor cell membrane through enhanced membrane fusion, thereby maintaining its PTT effect in tumor tissues. In vivo experiments demonstrate that RRIALP-C4 can effectively visualize tumor tissues and systemic blood vessels with a high sign-to-background ratio (SBR) to realize the synergistic treatment of thermochemotherapy by PTT synergistically with temperature-sensitive drug release. Therefore, the strategy of enhanced PTT through H-aggregation of NIR-II fluorophore in the tumor cell membrane has great potential for developing lipid nanosystems with integrated diagnosis and treatment function.

A lanthanide nanocomposite with cross-relaxation enhanced near-infrared emissions as a ratiometric nanothermometer

Lanthanide luminescence nanothermometers (LNTs) provide microscopic, highly sensitive, and visualizable optical signals for reporting temperature information, which is particularly useful in biomedicine to achieve precise diagnosis and therapy. However, LNTs with efficient emissions at the long-wavelength region of the second and the third near-infrared (NIR-II/III) biological window, which is more favourable for in vivo thermometry, are still limited. Herein, we present a lanthanide-doped nanocomposite with Tm³⁺ and Nd³⁺ ions as emitters working beyond 1200 nm to construct a dual ratiometric LNT. The cross-relaxation processes among lanthanide ions are employed to establish a strategy to enhance the NIR emissions of Tm³⁺ for bioimaging-based temperature detection in vivo. The dual ratiometric probes included in the nanocomposite have potential in monitoring the temperature difference and heat transfer at the nanoscale, which would be useful in modulating the heating operation more precisely during thermal therapy and other biomedical applications. This work not only provides a powerful tool for temperature sensing in vivo but also proposes a method to build high-efficiency NIR-II/III lanthanide luminescent nanomaterials for broader bio-applications.

Inducing Ring Complexation for Efficient Capture and Detection of Small Gaseous Molecules Using SERS for Environmental Surveillance

Gas-phase surface-enhanced Raman scattering (SERS) remains challenging due to poor analyte affinity to SERS substrates. The reported use of capturing probes suffers from concurrent inconsistent signals and long response time due to the formation of multiple potential probe-analyte interaction orientations. Here, we demonstrate the use of multiple non-covalent interactions for ring complexation to boost the affinity of small gas molecules, SO₂ and NO₂ , to our SERS platform, achieving rapid capture and multiplex detection down to 100 ppm. Experimental and in-silico studies affirm stable ring complex formation, and kinetic investigations reveal a 4-fold faster response time compared to probes without stable ring complexation capability. By synergizing spectral concatenation and support vector machine regression, we achieve 91.7 % accuracy for multiplex quantification of SO₂ and NO₂ in excess CO₂ , mimicking real-life exhausts. Our platform shows immense potential for on-site exhaust and air quality surveillance.

Design and Synthesis of Novel Raman Reporters for Bioorthogonal SERS Nanoprobes Engineering

Surface-enhanced Raman spectroscopy (SERS) exploiting Raman reporter-labeled nanoparticles (RR@NPs) represents a powerful tool for the improvement of optical bio-assays due to RRs’ narrow peaks, SERS high sensitivity, and potential for multiplexing. In the present work, starting from low-cost and highly available raw materials such as cysteamine and substituted benzoic acids, novel bioorthogonal RRs, characterized by strong signal (103 counts with FWHM < 15 cm−1) in the biological Raman-silent region (>2000 cm−1), RRs are synthesized by implementing a versatile, modular, and straightforward method with high yields and requiring three steps lasting 18 h, thus overcoming the limitations of current reported procedures. The resulting RRs’ chemical structure has SH-pendant groups exploited for covalent conjugation to high anisotropic gold-NPs. RR@NPs constructs work as SERS nanoprobes demonstrating high colloidal stability while retaining NPs’ physical and vibrational properties, with a limit of detection down to 60 pM. RR@NPs constructs expose carboxylic moieties for further self-assembling of biomolecules (such as antibodies), conferring tagging capabilities to the SERS nanoprobes even in heterogeneous samples, as demonstrated with in vitro experiments by transmembrane proteins tagging in cell cultures. Finally, thanks to their non-overlapping spectra, we envision and preliminary prove the possibility of exploiting RR@NPs constructs simultaneously, aiming at improving current SERS-based multiplexing bioassays.

Molecular Programming of NIR-IIb-Emissive Semiconducting Small Molecules for In Vivo High-Contrast Bioimaging Beyond 1500 nm

Materials with long-wavelength second near-infrared (NIR-II) emission are highly desired for in vivo dynamic visualizating of microstructures in deep tissues. Herein, by employing an atom-programming strategy, a series of highly fluorescent semiconducting oligomers (SOMs) with tunable NIR-IIb emissions are developed for bioimaging applications. After self-assembly into nanoparticles (NPs), they show good brightness, high photostability, and satisfactory biocompatibility. The SOM NPs are applied as probes for high-resolution imaging of whole-body and hind-limb blood vessels, biliary tract, and bladder with their emissions over 1500 nm. This work demonstrates an atom-programming strategy for constructing semiconducting small molecules with enhanced NIR-II fluorescence for deep-tissue imaging, affording new insight for advancing molecular design of NIR-II fluorophores.

Modularizable Liquid-Crystal-Based Open Surfaces Enable Programmable Chemical Transport and Feeding using Liquid Droplets

Droplet-based miniature reactors have attracted interest in both fundamental studies, for the unique reaction kinetics they enable, and applications in bio-diagnosis and material synthesis. However, the precise and automatic feeding of chemicals, important for the delicate reactions in these miniaturized chemical reactors, either requires complex, high-cost microfluidic devices or lacks the capability to maintain a pinning-free droplet movement. Here, the design and synthesis of a new class of liquid crystal (LC)-based open surfaces, which enable a controlled chemical release via a programmable LC phase transition without sacrificing the free transport of the droplets, are reported. It is demonstrated that their intrinsic slipperiness and self-healing properties enable a modularizable assembly of LC surfaces that can be loaded with different chemicals to achieve a wide range of chemical reactions carried out within the droplets, including sequential and parallel chemical reactions, crystal growth, and polymer synthesis. Finally, an LC-based chemical feeding device is developed that can automatically control the release of chemicals to direct the simultaneous differentiation of human induced pluripotent stem cells into endothelial progenitor cells and cardiomyocytes. Overall, these LC surfaces exhibit desirable levels of automation, responsiveness, and controllability for use in miniature droplet carriers and reactors.

Remote neural regulation mediated by nanomaterials

Neural regulation techniques play an essential role in the functional dissection of neural circuits and also the treatment of neurological diseases. Recently, a series of nanomaterials, including upconversion nanoparticles (UCNPs), magnetic nanoparticles (MNPs), and silicon nanomaterials (SNMs) that are responsive to remote optical or magnetic stimulation, have been applied as transducers to facilitate localized control of neural activities. In this review, we summarize the latest advances in nanomaterial-mediated neural regulation, especially in a remote and minimally invasive manner. We first give an overview of existing neural stimulation techniques, including electrical stimulation, transcranial magnetic stimulation, chemogenetics, and optogenetics, with an emphasis on their current limitations. Then we focus on recent developments in nanomaterial-mediated neural regulation, including UCNP-mediated fiberless optogenetics, MNP-mediated magnetic neural regulation, and SNM-mediated non-genetic neural regulation. Finally, we discuss the possibilities and challenges for nanomaterial-mediated neural regulation.

Engineering of Portable Smartphone Integrated with Liposome-Encapsulated Curcumin for Onsite Visual Ratiometric Fluorescence Imaging of Hypochlorite

Precisely onsite monitoring of hypochlorite (ClO^- ) is of great significance to guide its rational use, reducing/avoiding its potential threat toward food safety and human health. Considering ClO^- could quench fluorescence of curcumin (CCM) by oxidizing the o-methoxyphenol of CCM into benzoquinone, a portable ratiometric fluorescence sensor integrated with smartphone was designed for realizing the visual point-of-care testing (POCT) of ClO^- . The amphiphilic phospholipid polymer was used as carrier to wrap curcumin, forming a novel liposome-encapsulated CCM, which provided a scaffold to bind with [Ru(bpy)₃ ]²⁺ through electrostatic interaction, thus assembling [Ru(bpy)₃ ]²⁺ -functionalized liposome-encapsulated CCM ([Ru(bpy)₃ ]²⁺ @CCM-NPs). Further integrated with smartphone, visual imaging of [Ru(bpy)₃ ]²⁺ @CCM-NPs could be achieved and the accurate onsite detection of ClO^- could be realized with a detection limit of 66.31 nM and a linear range of 0.2210 to 80.0 μM. In addition, the sensor could monitor ClO^- in real samples with an onsite detection time of ∼154.0 s.

Ultra-sensitive dielectrophoretic surface charge multiplex detection inside a micro-dielectrophoretic device

Label-free dielectrophoretic force-based surface charge detection has shown great potential for highly sensitive and selective sensing of metal ions and small biomolecules. However, this method suffers from a complex calibration process and measurement signal interference in simultaneous multi-analyte detection, thus creating difficulties in multiplex detection. We have developed a method to overcome these issues based on the optical discrimination of the dielectrophoretic behaviors of multiple microparticle probes considering the surface charge difference before and after self-assembling conjugation. In this report, we demonstrate and characterize this dielectrophoretic force-based surface charge detection method with particle probes functionalized by various biomolecules. This technique achieved an attomolar limit of detection (LOD) for Hg²⁺ in distilled water and a femtomolar LOD in drinking water using DNA aptamer-functionalized particle probes. More importantly, using two different DNA aptamer-functionalized particle probes for Hg²⁺ and Ag⁺, label-free dielectrophoretic multiplex detection of these species in drinking water with a femtomolar and a nanomolar LOD was achieved for the first time.

Organic fluorescent nanoprobes with NIR-IIb characteristics for deep learning

Illumination of biological events with near-infrared II sub-channel (NIR-IIb, 1500-1700 nm) enhances the transparency of biological tissues, which is very attractive for deep imaging. Due to the long-wavelength, which reduces optical damage, suppresses autofluorescence, and obviates light scattering, NIR-IIb nanoprobes afford deep tissue penetration with unprecedented spatiotemporal resolution. Hence, NIR-IIb imaging facilitates deep learning and decipherment of biological proceedings in living organisms with astounding high clarity. In comparison to its predecessors in the visible-near-infrared spectrum, imaging in the NIR-IIb has shown great potential for tissue imaging and extrapolating imaging applications for clinical studies. However, the use of organic fluorescent nanoprobes (OFNPs) in the NIR-IIb region is still rare since it is in its early stages. Thus, herein we aim to survey the recent development of different organic fluorescent nanomaterials with NIR-IIb characteristics, their unique photophysical properties, and their utilization in deep imaging in animal models. Further, practical researches on organic fluorescent nanoprobes with NIR-IIb emission and their transition to clinical applications are highlighted.

Multiplexed Identification of Bacterial Biofilm Infections Based on Machine-Learning-Aided Lanthanide Encoding

Pathogenic biofilms are up to 1000-fold more drug-resistant than planktonic pathogens and cause about 80% of all chronic infections worldwide. The lack of prompt and reliable biofilm identification methods seriously prohibits the diagnosis and treatment of biofilm infections. Here, we developed a machine-learning-aided cocktail assay for prompt and reliable biofilm detection. Lanthanide nanoparticles with different emissions, surface charges, and hydrophilicity are formulated into the cocktail kits. The lanthanide nanoparticles in the cocktail kits can offer competitive interactions with the biofilm and further maximize the charge and hydrophilicity differences between biofilms. The physicochemical heterogeneities of biofilms were transformed into luminescence intensity at different wavelengths by the cocktail kits. The luminescence signals were used as learning data to train the random forest algorithm, and the algorithm could identify the unknown biofilms within minutes after training. Electrostatic attractions and hydrophobic-hydrophobic interactions were demonstrated to dominate the binding of the cocktail kits to the biofilms. By rationally designing the charge and hydrophilicity of the cocktail kit, unknown biofilms of pathogenic clinical isolates were identified with an overall accuracy of over 80% based on the random forest algorithm. Moreover, the antibiotic-loaded cocktail nanoprobes efficiently eradicated biofilms since the nanoprobes could penetrate deep into the biofilms. This work can serve as a reliable technique for the diagnosis of biofilm infections and it can also provide instructions for the design of multiplex assays for detecting biochemical compounds beyond biofilms.

Orthogonal Multiplexed NIR-II Imaging with Excitation-Selective Lanthanide-Based Nanoparticles

Multiplexed imaging in the second near-infrared (NIR-II, 1000-1700 nm) window, with much reduced tissue scattering and autofluorescence background noises, could offer comprehensive information for studying biological processes and accurate diagnosis. A critical requirement for harvesting the full potential of multiplexing is to develop fluorescent probes with emission profiles specifically tuned at distinct excitations toward their target applications. However, the lack of versatile probes with separated signals in this NIR-II window hinders the potential of in vivo multiplexed imaging. In this study, we designed three types of Nd³⁺-, Ho³⁺-, and Er³⁺-based down-shifting nanoparticles (DSNPs) with core-shell structures (csNd, csHo, and csEr). Excitation wavelengths of these nanoparticles were first screened and confirmed at 730, 915, and 655 nm. Under the new excitations, orthogonal three-color emissions in the NIR-II window (1060, 1180, and 1525 nm for csNd, csHo, and csEr, respectively) were efficiently achieved. These excitation-selective DSNPs were then demonstrated to be promising in encrypted anticounterfeiting applications with increased optical codes. By programmed administration of the DSNPs, anatomical rotation imaging can also be successfully performed to differentiate mouse bones, stomach, and blood vessels with high contrast and resolution in a fixed NIR-II channel (>1000 nm) by only switching the excitation wavelengths. This study suggests that the designed NIR-II excitation-selective DSNPs with orthogonal emissions may offer a powerful framework for spatially multiplexed imaging in biological and life sciences.

Printed Nanochain-Based Colorimetric Assay for Quantitative Virus Detection

Fast and ultrasensitive detection of pathogens is very important for efficient monitoring and prevention of viral infections. Here, we demonstrate a label-free optical detection approach that uses a printed nanochain assay for colorimetric quantitative testing of viruses. The antibody-modified nanochains have high activity and specificity which can rapidly identify target viruses directly from biofluids in 15 min, as well as differentiate their subtypes. Arising from the resonance induced near-field enhancement, the color of nanochains changes with the binding of viruses that are easily observed by a smartphone. We achieve the detection limit of 1 PFU μL^-1 through optimizing the optical response of nanochains in visible region. Besides, it allows for real-time response to virus concentrations ranging from 0 to 1.0×10⁵  PFU mL^-1 . This low-cost and portable platform is also applicable to rapid detection of other biomarkers, making it attractive for many clinical applications.

High-Fidelity NIR-II Multiplexed Lifetime Bioimaging with Bright Double Interfaced Lanthanide Nanoparticles

Fluorescence lifetime imaging provides more possibility of in vivo multiplexing in second near infrared (NIR-II) window. However, it still faces the obstacle that fluorescent probes with differentiable lifetime often exhibit quite different fluorescence intensity, especially the short lifetime usually accompanies with a weak fluorescence intensity, resulting in the difficulty for simultaneously decoding multiplexed lifetime information due to the interference of background noise. To facilitate high-fidelity lifetime multiplexed imaging, we developed a series of Er³⁺ doped double interface fluorescent nanoprobes (Er-DINPs): α-NaYF₄ @NaErF₄ : Ce@NaYbF₄ @NaErF₄ : Ce@NaYF₄ with strong fluorescence intensity and easily distinguishable fluorescence lifetime. Both in vitro and in vivo experimental results confirmed the advantage of these probes with comparable fluorescence intensity for high-fidelity multiplexed lifetime bioimaging.

Rigidity Bridging Flexibility to Harmonize Three Excited-State Deactivation Pathways for NIR-II-Fluorescent-Imaging-Guided Phototherapy

Small organic phototherapeutic molecules of the second near-infrared (NIR-II) window (1000-1700 nm) serve as promising candidates for theranostics. However, developing such versatile agents for fluorescence-guided photodynamic/photothermal therapy remains a demanding task stirred by competitive energy dissipation pathways, including radiative decay, internal conversion, and intersystem crossing. To the best of current knowledge, the current paradigm for addressing the issue has deliberately approached the optimum balance among three deactivation processes through offsetting from each other, possibly leading to a comprehensively compromised theranostic efficacy. Few reports aim to modulate the three deactivation pathways excluding sacrificing any one of them. Herein, a molecular design strategy to construct a phototherapeutic organic fluorophore CCNU-1060, armed with NIR-II luorescence-guided phototherapeutic properties, is rationally developed. With a flexible motor, tetraphenylethene, bridged to the rigidified coplanar core boron-azadipyrromethene, the desired CCNU-1060 is subsequently encapsulated into an amphiphilic matrix to form CCNU-1060 nanoparticles (NPs), which match or transcend its precursor NJ-1060 NPs in the three energy dissipation processes. CCNU-1060 NPs are utilized to realize high-spatial vessel imaging and effective NIR-II fluorescence-guided phototherapeutic tumor ablation. This study unlocks a viewpoint of molecular engineering that simultaneously regulates multiple energy dissipation pathways for the construction of versatile phototherapy agents.

Precise and convenient size barcode on microfluidic chip for multiplex biomarker detection

The existing multiplex biomarker detection methods are limited by the high demand for coding material and expensive detection equipment. This paper proposes a convenient and precise coding method based on a wedge-shaped microfluidic chip, which can be further applied in multiplex biomarker detection. The proposed microfluidic chip has a microchannel with continuously varying height, which can naturally separate and code microparticles of different sizes. Our data indicate that this method can be applied to code more than 5 or 7 kinds of microparticles, even when their size discrepancies are smaller than 1 μm. Based on these, multiplex biomarker detection can be implemented by using microparticles of different sizes, hence each kind of microparticle that coats one kind of antibody represents the species of targets. This method is simple and easy to operate, with no clogging or sophisticated coding design, showing its significant potential in the area of point-of-care tests (POCT).

Smart Nanozyme Platform with Activity-Correlated Ratiometric Molecular Imaging for Predicting Therapeutic Effects

Nanozymes with intrinsic enzyme-like characteristics have attracted enormous research interest in biological application. However, there is a lack of facile approach for evaluating the catalytic activity of nanozymes in living system. Herein, we develop a novel manganese-semiconducting polymer-based nanozyme (MSPN) with oxidase-like activity for reporting the catalytic activity of itself in acid-induced cancer therapy via ratiometric near-infrared fluorescence (NIRF)-photoacoustic (PA) molecular imaging. Notably, MSPN possess oxidase-like activity in tumor microenvironment, owing to the mixed-valent MnOx nanoparticles, which can effectively kill cancer cells. Because the semiconducting polymer (PFODBT) is conjugated with oxidase-responsive molecule (ORM), the catalytic activity of nanozyme can be correlated with the ratiometric signals of NIRF (FL₆₉₅ /FL₈₂₅ ) and PA (PA₆₈₀ /PA₇₈₀ ), which may provide new ideas for predicting anticancer efficacy of nanozymes in living system.