To explore the pathogenesis of anterior resection syndrome by magnetic resonance imaging rectal defecography.

BACKGROUND: Over 90% of rectal cancer patients develop low anterior resection syndrome (LARS) after sphincter-preserving resection. The current globally recognized evaluation method has many drawbacks and its subjectivity is too strong, which hinders the research and treatment of LARS. AIM: To evaluate the anorectal function after colorectal cancer surgery by quantifying the index of magnetic resonance imaging (MRI) defecography, and pathogenesis of LARS. METHODS: We evaluated 34 patients using the standard LARS score, and a new LARS evaluation index was established using the dynamic images of MRI defecography to verify the LARS score. RESULTS: In the LARS score model, there were 10 (29.41%) mild and 24 (70.58%) severe cases of LARS. The comparison of defecation rate between the two groups was 29.36 ± 14.17% versus 46.83 ± 18.62% (P = 0.004); and MRI-rectal compliance (MRI-RC) score was 3.63 ± 1.96 versus 7.0 ± 3.21 (P = 0.001). Severe and mild LARS had significant differences using the two evaluation methods. There was a significant negative correlation between LARS and MRI-RC score (P < 0.001), and they had a negative correlation with defecation rate (P = 0.028). CONCLUSION: MRI defecography and standard LARS score can both be used as an evaluation index to study the pathogenesis of LARS.

Fabrication of multifunctional g-C3N4-modified Au/Ag NRs arrays for ultrasensitive and recyclable SERS detection of bisphenol A residues.

Monolayer g-C3N4-modified Au/Ag nanorods (g-C3N4/Au/Ag NRs) array is fabricated as a dual-function platform with high surface-enhanced Raman scattering (SERS) response and excellent photocatalytic degradation ability for bisphenol A (BPA) residues. FDTD simulation results of Au/Ag NRs proves that the electromagnetic field intensity is significantly enhanced at the gap of Ag NRs and Au NPs and the protrusion of Au NPs, which endows the arrays with excellent SERS activity. The arrays exhibit high sensitivity for rhodamine 6G (R6G) (LOD = 1.1 × 10-11 mol/L) and high SERS enhancement (EF = 9.2 × 107). In addition, the g-C3N4/Au/Ag NRs could degrade ˃90% of BPA adsorbed on the substrate surface within 140 min under visible light irradiation, and maintains its SERS activity after repeated use for 4 times. The dual-function platform with high SERS response and excellent recycling capability is proved to be reliable and is very promising for monitoring of BPA residues in food.

PEC-SERS Dual-Mode Detection of Foodborne Pathogens Based on Binding-Induced DNA Walker and C3N4/MXene-Au NPs Accelerator.

In this paper, a photoelectrochemical (PEC)-surface-enhanced Raman scattering (SERS) dual-mode biosensor is constructed coupled with a dual-recognition binding-induced DNA walker with a carbon nitride nanosheet (C3N4)/MXene-gold nanoparticles (C/M-Au NPs) accelerator, which is reliable and capable for sensitive and accurate detection of Staphylococcus aureus (S. aureus). Initially, a photoactive heterostructure is formed by combining C3N4 and MXene via a simple electrostatic self-assembly as they possess well-matched band-edge energy levels. Subsequently, in situ growth of gold nanoparticles on the formed surface results in better PEC performance and SERS activity, because of the synergistic effects of surface plasmon resonance and Schottky barrier. Furthermore, a three-dimensional, bipedal, and dual-recognition binding-induced DNA walker is introduced with the formation of Pb2+-dependent DNAzyme. In the presence of S. aureus, a significant quantity of intermediate DNA (I-DNA) is generated, which can open the hairpin structure of Methylene Blue-tagged hairpin DNA (H-MB) on the electrode surface, thereby enabling the switch of signals for the quantitative determination of S. aureus. The constructed PEC-SERS dual-mode biosensor that can be mutually verified under one reaction effectively addresses the problem of the low detection accuracy of traditional sensors. Experimental results revealed that the effective combination of PEC and SERS is achieved for amplification detection of S. aureus with a detection range of 5-108 CFU/mL (PEC) and 10-108 CFU/mL (SERS), and a detection of limit of 0.70 CFU/mL (PEC) and 1.35 CFU/mL (SERS), respectively. Therefore, this study offers a novel and effective dual-mode sensing strategy, which has important implications for bioanalysis and health monitoring.

Designing carbon nanotube sponge/Au@MgO2 for surface-enhanced Raman scattering detection and fenton-like degradation of organic pollutants.

With the acceleration of industry and agriculture process, the massive emission of organic pollutants is a major problem which seriously restricts the sustainable development of society. Rapid enrichment, efficient degradation and sensitive detection are three key steps to solve the problem of organic pollutants, while developing a simple method integrating the above three capabilities is still a challenge. Herein, a three-dimensional carbon nanotube sponge decorated with magnesium peroxide and gold nanoparticles (CNTs/Au@MgO2 sponge) was prepared for surface enhanced Raman scattering (SERS) detection and degradation of aromatic organics by advanced oxidation processes. The CNTs/Au@MgO2 sponge with porous structures adsorbed molecules rapidly through π-π and electrostatic interaction, thus more aromatic molecules were driven to the hot-spot areas for highly sensitive SERS detection. A detection of limit with 9.09 × 10-9 M was achieved for rhodamine B (RhB). The adsorbed molecules were degraded by an advanced oxidation process utilizing hydrogen peroxide produced by MgO2 nanoparticles under acidic condition with 99% efficiency. In addition, the CNTs/Au@MgO2 sponge exhibited high reproducibility with the relative standard deviation (RSD) at 1395 cm-1 of approximately 6.25%. The results showed the sponge can be used to effectively track the concentration of pollutants during the degradation process and maintain the SERS activity by re-modifying Au@MgO2 nanomaterials. Furthermore, the proposed CNTs/Au@MgO2 sponge demonstrated the simultaneous functions of enrichment, degradation, and detection for aromatic pollutants, thus significantly expanding the potential applications of nanomaterials in environmental analysis and treatment.

Highly selective and sensitive surface-enhanced Raman scattering sensors for the detection of peroxynitrite in cells.

In the physiological and pathological processes, evaluating the role of peroxynitrite (ONOO-) in living cells with high sensitivity and selectivity is a significant challenge. In this study, a highly sensitive surface-enhanced Raman spectroscopy sensor (SERS) was proposed using 3-methoxyphenylborate pinacol ester (MAPE) modified gold nanoflowers (Au NFs/MAPE) for the detection of ONOO- in living cells. The principle of the nanosensor is based on ONOO- which can oxidize aryl boric acid on Au NFs to release phenol, resulting in changes in the SERS spectrum of the sensors. The results show that the SERS sensors have high selectivity and excellent sensitivity for ONOO- in the presence of other interfering ions. The detection limit of the sensors is as low as 0.48 µM, which can meet the needs in biological systems. In addition, the SERS sensors have long-term stability and high biocompatibility. More importantly, this sensor can successfully monitor active biological samples and detect the ONOO- content generated during an oxidative stress reaction, creating a new method for studying cell biochemistry.

Peroxidase-like Nanozymes for Point-of-Care SERS Sensing and Wound Healing.

The emergence of nanozymes provides a potential method for combating multidrug-resistant bacteria resulted from the abuse of antibiotics. However, in nanozyme-catalyzed systems, few studies have addressed the actual hydrogen peroxide (H2O2) level involved in sterilization. Herein, we designed a high-efficiency peroxidase-mimicking nanozyme with surface-enhanced Raman scattering (SERS) property by assembling gold nanoparticles on single-layer Cu2+-C3N4 (AuNP-Cu2+-C3N4). The nanozyme effectively converts the low-active Raman reporter 3,3',5,5'-tetramethylbenzidine (TMB) into its oxidized form with H2O2, resulting in SERS signal changes, thereby achieving highly sensitive quantification of H2O2 with limit of detection as low as 0.60 µM. More importantly, the nanozyme can specifically catalyze H2O2 into antibacterial hydroxyl radicals. In vitro and in vivo evaluations demonstrate the remarkable antibacterial efficacy of the nanozyme/H2O2 combination against Staphylococcus aureus (up to 99.9%), which could promote wound healing in mice and allow point-of-care monitoring the amount of H2O2 participated in effective sterilization. This study not only displays great potential in combining multiple functionalities of nanomaterials for versatile bioassays but also provides a promising approach to design nanozymes for biomedical and catalytic applications.

Highly sensitive AuNSs@AgNR SERS substrates for rapid determination of aromatic amines.

The leakage of aromatic amines will pose a great threat to human health and the ecological environment. Therefore, there is an urgent need to achieve rapid and high-sensitivity detection of such substances. In this study, a simple surface-enhanced Raman scattering (SERS) method based on gold nanostars-modified silver nanorods (AuNSs@AgNRs) was established for the detection of benzidine and 4-aminobiphenyl (4-ABP). The enhancement factors of the substrate towards rhodamine 6G (R6G) and crystal violet (CV) were 4.67 × 108 and 1.11 × 108, respectively. Combined with density functional theory (DFT), the AuNSs@AgNR substrate achieved the rapid detection of benzidine and 4-ABP and obtained low detection limits (LODbenzidine = 7.09 × 10-9 M; LOD4-ABP = 1.20 × 10-9 M). Furthermore, the AuNSs@AgNR substrate can realize the high-sensitivity detection of benzidine and 4-ABP in the spiked river water samples within 3 min, which means that the AuNSs@AgNR-based SERS method can be used as a portable platform to realize the on-site rapid detection of environmental pollutants.

Highly selective SERS detection of acetylcholinesterase in human blood based on catalytic reaction.

Acetylcholinesterase (AChE) is a key hydrolase in the cholinergic system, which directly determines the degradation of neurotransmitters. Therefore, it is a significant challenge to detect AChE in human blood with high sensitivity and selectivity in physiological and pathological processes. A novel nanoprobe by decorating the surface of gold nanoparticles with neostigmine (NE) AuNPs/NE was constructed for the AChE assay in serum. The principle is based on the specific recognition and cleavage of carbamate bonds in AuNPs/NE by AChE to form hydroxyl groups, resulting in changes of SERS spectra. The results show that 10 nm AuNPs/NE exhibit excellent catalytic activity for this reaction and the reaction rate is six times higher than that of 70 nm AuNPs/NE. Benefiting from the combined advantages of catalytic reaction specificity and molecular finger printing provided by SERS technology, AuNPs/NE exhibit high selectivity for AChE. The limit of detection (LOD) of this method for AChE activity was low to 0.02 U/mL. In addition, the spiked recovery of AChE in serum samples was 75.0%-119.2%. The proposed sensor also exhibits long-term stability and high biocompatibility with the increasing incubation time. More importantly, this work provides a new perspective for elucidating the role of AChE regulated by oxidative stress in the pathology of depression.

Nanozyme-mediated signal amplification for ultrasensitive photoelectrochemical sensing of Staphylococcus aureus based on Cu-C3N4-TiO2 heterostructure.

Food-borne pathogens are one of the leading causes of food poisoning, which vigorously affect food safety and human health. Therefore, the development of early and rapid detection methods for food pollution evaluation is the key to food safety and quality control. Herein, a simple and inexpensive photoelectrochemical (PEC) sensor is developed for highly selective and ultrasensitive detection of Staphylococcus aureus (S. aureus). The technique is based on "signal-off" that employs Cu-C3N4-TiO2 heterostructures as photoactive materials and monolayer Cu-C3N4 nanozyme as a signal amplifier. In the presence of S. aureus, the aptamer-modified Cu-C3N4 (Cu-C3N4@Apt, a signal amplifier) and S. aureus were specifically anchored on the surface of the ligand-modified photoelectrode. The Cu-C3N4@Apt nanozyme acted as a peroxidase to catalyze the oxidation of 4-chloro-1-naphthol (4-CN) to produce insoluble precipitate on the electrode surface and resulted in a significant decrease in photocurrent. Based on the signal-amplification by the Cu-C3N4@Apt nanozyme, the constructed PEC sensor demonstrated a wide linear range between 10-108 CFU/mL for the S. aureus detection with the detection limit (LOD) as low as 3.40 CFU/mL. Furthermore, the PEC sensor was capable of determining S. aureus in spiked orange juice and milk, with the recovery of 91%-113%, indicating the reliability of the sensor for S. aureus detection in real samples. This investigation provides a feasible strategy for the design of highly selective and ultrasensitive PEC sensors to determine analytes in complex systems.

The rs13075270 and rs13092160 polymorphisms of CCR1 and CCR3 genes on oral aphthous-like lesions in PFAPA syndrome.

Fever is a common symptom of infection in children. Periodic fever syndromes are less common but more complex. One of these Periodic fever syndromes is PFAPA (periodic fever, aphthous stomatitis, pharyngitis, cervical adenitis) syndrome which is known as the most benign syndromes. The cause of this disease is unknown. Various factors, including environmental and genetic factors, are involved in the development of this disease. In this study, the association of rs13075270 and rs13092160 polymorphisms were investigated in CCR1 and CCR3 genes with susceptibility to this syndrome in the Chinese population. In this regard, 38 patients with PFAPA syndrome and 100 healthy individuals were selected. After DNA sampling and extraction, polymorphisms of CCR1 and CCR3 receptor genes were examined by the PCR-RFLP method. Findings were analyzed using SPSS software version 22 with a significant level of P <0.05. The frequency of T/T genotype rs13092160 polymorphism in the patient and control groups was 78.95% and 83%, respectively, C/T genotype was 21.05% and 17% (P = 0.421). The frequency of the C/C genotype was 0 in both groups. Regarding rs13075270 polymorphism, the frequency of T/T genotype in patient and control groups was 15.79% and 81%, C/T genotype was 78.95% and 18% and C/C genotype was 5.26% and 1%, respectively (P<0.05). Thus, in rs13075270 polymorphism, the C/T genotype was associated with the risk of PFAPA syndrome (P<0.05), but rs13092160 polymorphism did not show a significant difference between individuals with PFAPA syndrome and controls.

Rapid and non-invasive surface-enhanced Raman spectroscopy (SERS) detection of chlorpyrifos in fruits using disposable paper-based substrates charged with gold nanoparticle/halloysite nanotube composites.

Chlorpyrifos is one of the most widely used organophosphate insecticides in agricultural production. Nevertheless, the residues of chlorpyrifos in agricultural by-product seriously threaten human health. Thus, the ultrasensitive detection of chlorpyrifos residues in agri-food products is of great demand. Herein, an AuNP/HNT-assembled disposable paper SERS substrate was prepared by an electrostatic self-assembly method to detect chlorpyrifos residues. The AuNP/HNT paper substrate exhibited high SERS activity, good reproducibility, and long-term stability, which was successfully used for quantitative detection of chlorpyrifos; the detection limit reached 7.9 × 10-9 M. For spiked apple samples the calculated recovery was 87.9% with a RSD value of 6.1%. The excellent detection ability of AuNP/HNT paper-based SERS substrate indicated that it will play an important role in pesticide detection in the future. AuNP/HNT assembled disposable paper SERS substrate was prepared by an electrostatic self-assembly method to detect chlorpyrifos residues in fruits.

Reusable ring-like Fe3O4/Au nanozymes with enhanced peroxidase-like activities for colorimetric-SERS dual-mode sensing of biomolecules in human blood.

Peroxidase-like nanozymes have led to important progress in biosensing, but most of nanozyme sensing systems are currently established by a single-signal output mode, which is susceptible to environmental and operational factors. Thus construction of a dual-signal output nanozyme sensing system is essential for obtaining reliable and robust performance. In this study, a novel peroxidase mimicking nanozyme was developed by decorating magnetic ring-like Fe3O4 with gold nanoparticles (R-Fe3O4/Au) for the colorimetric and surface-enhanced Raman scattering (SERS) dual-mode detection of biomolecules in human serum. The R-Fe3O4/Au nanozymes served as mimetic peroxidase which can catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine by hydrogen peroxide, and concomitantly as SERS substrates for detecting the Raman signals of oxidized products, providing an effective approach to investigate the reaction kinetics of enzymes. Based on the redox reactions, the nanozymes achieved colorimetric-SERS dual-mode sensing of glutathione (GSH) and cholesterol with detection limits as low as 0.10 µM and 0.08 µM, respectively. Furthermore, the nanozymes enabled rapid detection of GSH and cholesterol in serum without any complicated sample pretreatment. The R-Fe3O4/Au catalyst still displayed excellent peroxidase activity even after repeated use for 5 times. The proposed colorimetric-SERS dual-mode sensors exhibited good accuracy and reproducibility, which provides a new avenue for exploiting multifunctional sensors and has a great application prospect in biosensing.

Esterified-sawdust decorated with AgNPs as solid-phase extraction membranes for enrichment and high-sensitivity detection of polychlorinated biphenyls.

Polychlorinated biphenyls (PCBs) are a class of persistent organic pollutants, which cause serious harm to human health and ecological environment. Thus, a low-cost membrane was developed for highly effective removal and rapid surface-enhanced Raman scattering (SERS) detection of PCBs by filling esterified-sawdust (CA-SD) modified with silver nanoparticles (AgNPs) into solid phase extraction (SPE) column. SD was first modified by an esterification cross-linking strategy and then AgNPs were anchored on the CA-SD to prepare highly sensitive and reproducible SERS substrates (AgNPs/CA-SD). Due to the contraction of the surface area of the CA-SD caused by drying, the gap between the AgNPs could be reduced, thereby generating a large number of hot spots and driving more target molecules into them to obtain the enhanced SERS signals. The AgNPs/CA-SD-based SPE membrane showed excellent SERS activity with an enhancement factor of 5.98 × 108 for the R6G analysis. The proposed SERS-active SPE membrane with functionalization of mercapto-ß-cyclodextrin was further developed for the determination of PCB-77 and PCB-1 with the LODs of 1.43 × 10-9 M and 2.12 × 10-8 M, respectively. In addition, each PCB in the mixed sample could be quickly distinguished based on the characteristic peaks. The current research exhibits great potential for the simultaneous detection of multiple environmental contaminants and can meet the needs of on-site emergency detection.

Highly sensitive SERS substrates with multi-hot spots for on-site detection of pesticide residues.

Pesticide residues will be a huge threat to food security and ecological environment; therefore, there is an urgent need to achieve rapid and on-site detection of pesticide residues. Herein, a plasmonic substrate with multiple "hot spots" was fabricated by transferring three-dimensional (3D) Au nanoparticles (NPs) onto the polydimethylsiloxane (PDMS) membrane for highly sensitive surface-enhanced Raman scattering (SERS) detection of pesticide residues. In combination with 3D-FDTD simulations, high SERS enhancement (EF = 1.2 × 108) and high detection sensitivity (LOD = 6.3 × 10-10 M) were achieved, mainly due to the enhanced electromagnetic fields around the "hot spots". Additionally, the PDMS-based SERS substrate held good transparency and flexibility, enabling conformal contact with non-planar surfaces and allowing the laser to penetrate the back of the analytes. Combined with a portable Raman spectrometer, the substrates holds great potential for rapid, high-sensitive, and on-site detection of contaminants in food, especially for the analyte on the nonplanar surfaces.

Ultrasensitive SERS detection of exhaled biomarkers of lung cancer using a multifunctional solid phase extraction membrane.

The construction and clinical application of a surface-enhanced Raman scattering (SERS) platform for the early diagnosis of lung cancer could improve the survival rate of patients and would be of great significance. Nevertheless, a sensitive and reusable method for the detection of aldehydes, as biomarkers of lung cancer, in exhaled breath is still an enormous challenge. Aldehydes generally have a low cross section in Raman scattering and have a weak specific affinity to plasmonic nanoparticle surfaces, meaning that sensing them at low concentrations is incredibly difficult. Herein, an ultrasensitive SERS strategy, that can be recycled for further use, for the detection of lung cancer biomarkers in the form of aldehydes was realized by fabrication of a multifunctional Ag NPs@ZIF-67/g-C3N4 solid phase extraction (SPE) membrane. Based on the change in the vibrational fingerprints of 4-ATP before and after reaction with the aldehydes, the SPE membrane was successfully used for the ultrasensitive detection of aldehydes with a detection limit of 1.35 nM. The excellent SERS performance was attributed to the synergistic effect of the densely and closely distributed Ag NPs (providing SERS "hot spots"), ZIF-67 (concentrating the analyte molecules) and g-C3N4 (forming a membrane to prolong the contact time between the aldehydes and the substrate). In addition, recycling of the SPE membrane was achieved by utilizing the self-cleaning ability of the Ag NPs@ZIF-67/g-C3N4 membrane originating from the photocatalytic properties of g-C3N4. The proposed SERS membrane was easy to operate, rapid and portable, thus providing a potential tool for a point-of-care test in clinical and diagnostic practice.

Recent advances in graphene nanoribbons for biosensing and biomedicine.

In recent years, a new type of quasi-one-dimensional graphene-based material, graphene nanoribbons (GNRs), has attracted increasing attention. The limited domain width and rich edge configurations of GNRs endow them with unique properties and wide applications in comparison to two-dimensional graphene. This review article mainly focuses on the electrical, chemical and other properties of GNRs, and further introduces the typical preparation methods of GNRs, including top-down and bottom-up strategies. Then, their biosensing and biomedical applications are highlighted in detail, such as biosensors, photothermal therapy, drug delivery, etc. Finally, the challenges and future prospects in the synthesis and application of functionalized GNRs are discussed. It is expected that GNRs will have significant practical use in biomedical applications in the future.

Combined Paper Centrifugal Chromatographic Separation and SERS Detection for Multicomponent Substances.

The separation and chemical analysis of mixtures in an emergency situation represent major challenges, especially in remote or poverty-stricken areas. A novel method was developed for the rapid separation and detection of multiple components via paper centrifugal chromatography, which costs as little as $2.26 US. The method was realized based on the combination of portable paper centrifugal chromatography and surface-enhanced Raman scattering (SERS) detection. This coupled technique was successfully implemented for the separation and qualitative analysis of a rhodamine 6G-crystal violet mixture and a colorless aniline-pyrocatechol-benzidine mixture. A chromatographic mobile phase was collected using absorbent cotton, which was demonstrated to have no effect on the SERS results. The optimized device achieved rapid and effective separation of the colorless aniline-pyrocatechol-benzidine mixture with a high centrifugal force (0.3303π2 N). The newly developed method involving multicomponent paper centrifugal chromatography-SERS detection will be of great value for emergency-related substance separation and analysis in remote and poor areas.

Two-dimensional MXene modified AgNRs as a surface-enhanced Raman scattering substrate for sensitive determination of polychlorinated biphenyls.

Ultrathin two-dimensional MXene nanosheets were decorated on the surface of silver nanorods (AgNRs) through a facile modification strategy to prepare highly sensitive and reproducible SERS substrates (AgNR/MXene substrate). The MXene nanosheets could suppress the oxidation of the silver nanorods, which endows the substrate with good stability and reproducibility. Due to the strong interaction between AgNR/MXene and the analytes, the substrate also exhibited high SERS performance with the limit of detection (LOD) of crystal violet (CV) as low as 2.48 × 10-11 M. In particular, the AgNR/MXene substrate enabled on-site determination of 3,3',4,4'-tetrachlorobiphenyl (PCB-77) and 4-chlorobiphenyl (PCB-3) and the LODs were low at 2.43 × 10-10 and 2.14 × 10-9 M, respectively. In addition, the AgNR/MXene substrate could be used for the detection of single-component and multi-component PCBs in real soil samples with good recovery percentages (90.3% and 91.6% for PCB-3 and PCB-77 in single-component format, 108.1% and 106.5% for PCB-3 and PCB-77 in multi-component format). The AgNR/MXene substrate combines the synergistic properties of both AgNRs and MXene, showing great potential in simultaneous SERS detection of multiple pollutants at the point of need.

A disposable paper-based hydrophobic substrate for highly sensitive surface-enhanced Raman scattering detection.

Detection of target analytes with high sensitivity and reproducibility remains a challenge for surface-enhanced Raman scattering (SERS) due to the lack of cost-effective and highly sensitive substrates. In this study, a hydrophobic SERS substrate capable of concentrating nanoparticles and analytes was prepared by spin-coating lubricating liquid onto commercial paper. The condensation effect of the paper-based hydrophobic substrate induced aggregation of gold nanoparticles (Au NPs) to generate ''hot spots'' for SERS and to drive analytes to the hot-spot areas for more sensitive detection. The obtained SERS signal intensity was 5-fold higher than that obtained using common paper, and a detection limit (LOD) of 4.3 × 10-10 M for rhodamine 6G (R6G) was achieved. Randomly selected points on the substrate and different batches of substrates all exhibited high reproducibility, and the relative standard deviation (RSD) at 1362 cm-1 is approximately 11%. A further application of the hydrophobic substrate was demonstrated by the detection of cytochrome C within a linear detection range of 3.90 × 10-8 M-1.25 × 10-6 M. In addition, the prepared substrate can obtain identifiable SERS spectra of cancer cells and non-cancer cells because a large number of AuNP or Au NPs clusters can adhere to cells, resulting in the construction of a 3D hotspot matrix. The disposable hydrophobic paper substrate eliminates the problem of solution diffusion, and also provides an effective platform for biomolecular screening detection.

Fabrication of paper-based SERS substrates by spraying silver and gold nanoparticles for SERS determination of malachite green, methylene blue, and crystal violet in fish.

A disposable surface-enhanced Raman scattering (SERS) substrate was prepared by successively spraying silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) onto commercial filter paper using an inexpensive consumer sprayer. The strong surface enhancement of AgNPs and chemical stability of AuNPs can be advantageously combined. The substrate exhibited excellent SERS activity for malachite green (MG), methylene blue (MB), and crystal violet (CV) under 785-nm excitation, with limits of detection (LODs) of 4.3 × 10-9, 2.0 × 10-8, and 8.1 × 10-8 M, respectively. The substrate exhibited long-term stability, and it can be stored under ambient conditions for 4 weeks with a relative standard deviation of less than 3% among peak intensities. The substrate also showed good reproducibility with a relative standard deviation of 7.1% among different substrate peak intensities. The substrates enable on-site determination of residual fishery drugs and distinguish MG, MB, and CV mixtures in spiked fish within 5 min, and the average recoveries in fish scales and fish meat were better 90.1% and 76.9%, respectively. The method exhibited rapidity, simplicity, and high sensitivity and is expected to be used for the screening of additives in food.