Sensitive surface enhanced Raman scattering multiplexed detection of matrix metalloproteinase 2 and 7 cancer markers

Fano enhancement of SERS for rapid early diagnosis of colorectal cancer

Patients benefit greatly from early detection of colorectal cancer, but present diagnostic procedures have high costs, low sensitivity, and low specificity. However, it is still difficult to develop a strategy that can effectively detect cancer early using high-throughput blood analysis. Fano resonance-boosted SERS platform label-free serum creates an effective diagnostic system at the point of care. We obtained 220 high-quality SERS serum spectral datasets from 88 healthy volunteers and 132 patients with colorectal cancer. The biomarker detected in serum was further evaluated using 100 colorectal cancer tissues and adjacent normal intestinal tissues collected from West China Biobanks, West China Hospital, Sichuan University. The results showed that in 97 out of 100 paired samples, the biomarkers were successfully detected using the SERS platform. This demonstrates that Fano resonance-based SERS is highly effective for diagnosing colorectal cancer.

Study of the relationship among biomarkers, cell and tissue of glioma through Raman spectroscopy

Glioma is the most common brain tumors with high mortality and recurrence rates. Currently, the diagnosis methods for glioma are mainly based on tissue level, cellular level and biomarker level. In this paper, the characteristics of biomarkers (γ-aminobutyric acid and matrix mtalloproteinses-2), U87MG glioma cell and tissue were studied based on Raman spectroscopy, respectively. The results showed that the γ-aminobutyric acid concentration exhibited a linear relation with the intensity of characteristic peaks in 800-1600 cm-1 region, whereas the spectral baseline increased with the increasing of sample concentration in 200-700 cm-1 region. The Raman characteristics of matrix mtalloproteinses-2 in 20-1800 cm-1 region was investigated. Especially, it is demonstrated that the matrix mtalloproteinses-2 showed sixteen low-wavenumber Raman peaks in the range of 20-300 cm-1. Moreover, the U87MG glioma cell showed seven different Raman characteristic peaks in 600-1800 cm-1 region. Compared with the normal tissue, the Raman intensity of tumor tissue showed apparent intensity differences in 300-1800 cm-1, where the intensity changes of these Raman peaks were related to the reducing of the lipid metabolic pathways, and increase of the RNA in tumor tissue region. Furthermore, it is found that the Raman spectra of U87MG glioma cell and tumor tissue had corresponding peaks in the Raman spectra of the liquid γ-aminobutyric acid and matrix mtalloproteinses-2. It is suggested that the γ-aminobutyric acid and matrix mtalloproteinses-2 contributed to the formation and growth of glioma cell and tissue. Thus, Raman spectroscopy not only can diagnose glioma at the biomarkers, cellular and tissue level, but also analyze the relationship among the three. Furthermore, the results provided a physical marker for the detection of glioma in clinically.

Idiopathic pulmonary fibrosis (IPF): Diagnostic routes using novel biomarkers

Idiopathic pulmonary fibrosis (IPF) diagnosis is still the diagnosis of exclusion. Differentiating from other forms of interstitial lung diseases (ILDs) is essential, given the various therapeutic approaches. The IPF course is now unpredictable for individual patients, although some genetic factors and several biomarkers have already been associated with various IPF prognoses. Since its early stages, IPF may be asymptomatic, leading to a delayed diagnosis. The present review critically examines the recent literature on molecular biomarkers potentially useful in IPF diagnostics. The examined biomarkers are grouped into breath and sputum biomarkers, serologically assessed extracellular matrix neoepitope markers, and oxidative stress biomarkers in lung tissue. Fibroblasts and complete blood count have also gained recent interest in that respect. Although several biomarker candidates have been profiled, there has yet to be a single biomarker that proved specific to the IPF disease. Nevertheless, various IPF biomarkers have been used in preclinical and clinical trials to verify their predictive and monitoring potential.

Nanoplasmonic biosensors for precision medicine

Nanoplasmonic biosensors have a huge boost for precision medicine, which allows doctors to better understand diseases at the molecular level and to improve the earlier diagnosis and develop treatment programs. Unlike traditional biosensors, nanoplasmonic biosensors meet the global health industry's need for low-cost, rapid and portable aspects, while offering multiplexing, high sensitivity and real-time detection. In this review, we describe the common detection schemes used based on localized plasmon resonance (LSPR) and highlight three sensing classes based on LSPR. Then, we present the recent applications of nanoplasmonic in other sensing methods such as isothermal amplification, CRISPR/Cas systems, lab on a chip and enzyme-linked immunosorbent assay. The advantages of nanoplasmonic-based integrated sensing for multiple methods are discussed. Finally, we review the current applications of nanoplasmonic biosensors in precision medicine, such as DNA mutation, vaccine evaluation and drug delivery. The obstacles faced by nanoplasmonic biosensors and the current countermeasures are discussed.

Signal-On Mass Spectrometric Biosensing of Multiplex Matrix Metalloproteinases with a Phospholipid-Structured Mass-Encoded Microplate

The detection of matrix metalloproteinases (MMPs) is of great importance for diagnosis and staging of cancer. This work proposed a signal-on mass spectrometric biosensing strategy with a phospholipid-structured mass-encoded microplate for assessment of multiplex MMP activities. The designed substrate and internal standard peptides were subsequently labeled with the reagents of isobaric tags for relative and absolute quantification (iTRAQ), and DSPE-PEG(2000)maleimide was embedded on the surface of a 96-well glass bottom plate to fabricate the phospholipid-structured mass-encoded microplate, which offered a simulated environment of the extracellular space for enzyme reactions between MMPs and the substrates. The strategy achieved multiplex MMP activity assays by dropping the sample in the well for enzyme cleavages, followed by adding trypsin to release the coding regions for ultrahigh performance liquid chromatography-tandem mass spectrometric (UHPLC-MS/MS) analysis. The peak area ratios of released coding regions and their respective internal standard (IS) peptides exhibited satisfied linear ranges of 0.05-50, 0.1-250, and 0.1-100 ng mL^-1 with the detection limits of 0.017, 0.046, and 0.032 ng mL^-1 for MMP-2, MMP-7, and MMP-3, respectively. The proposed strategy demonstrated good practicability in inhibition analysis and detections of multiplex MMP activities in serum samples. It is of great potential for clinical applications and can be expanded for multiplex enzyme assays.

Comprehensive Analysis of the Prognostic Value of Circulating MMP-7 Levels in Urothelial Carcinoma: A Combined Cohort Analysis, Systematic Review, and Meta-Analysis

Lymph node (LN) status is the most significant prognostic factor for invasive urothelial bladder cancer (UBC); however, the optimal extent of LN dissection (LND) is debated. We assessed circulating matrix metalloproteinase-7 (MMP-7) as a prognostic factor and decision-making marker for the extent of LND. Preoperative serum MMP-7 levels were determined in two independent UBC cohorts (n = 188; n = 68) and in one control cohort (n = 97) by using the ELISA method. A systematic review and meta-analysis on the prognostic role of circulating pretreatment MMP-7 levels were performed. Serum MMP-7 levels were higher in patients compared to controls (p < 0.001) with the highest levels in LN-positive cases. Half of LN-positive UBC patients had low MMP-7 levels, whereas the survival of LN-negative patients with high serum MMP-7 findings was poor. MMP-7 levels were independently associated with poor survival in both cohorts (p = 0.006, p < 0.001). Accordingly, our systematic review of six eligible publications revealed a 2.5-fold higher mortality risk in patients with high MMP-7 levels. In conclusion, preoperative MMP-7 level is a validated and independent prognostic factor in urothelial cancer. It cannot be used to decide between regional or extended LND but may be useful in identifying LN-negative high-risk patients with potentially undetected metastases.

Mass-Encoded Suspension Array for Multiplex Detection of Matrix Metalloproteinase Activities

This work designed a mass spectrometric biosensing strategy for the multiplex detection of matrix metalloproteinases (MMPs) with a mass-encoded suspension array. This array was fabricated as multiplex sensing probes by functionalizing magnetic beads with MMP-specific peptide-isobaric tags for relative and absolute quantification (iTRAQ) conjugates, which contained a hexahistidine tag for surface binding, a substrate region for MMP cleavage, and a coding region for the specific MMP. The integration of the multiplex coding ability of iTRAQ with ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and the proteolysis method for peptide digestion endowed the biosensing method with high throughput and ultrahigh sensitivity. This strategy could be conveniently performed by mixing the sample and the suspension array for enzymatic reactions and then digesting the uncleaved peptides with trypsin to release the coding regions for UPLC-MS/MS analysis. With MMP-2 and MMP-7 as analytes, the relative changes of peak area ratios of coding regions showed good linear responses in the ranges of 0.2-100 and 0.5-400 ng mL^-1, with detection limits of 0.064 and 0.17 ng mL^-1, respectively. The analysis of MMP activity in serum samples and its change responding to inhibitors demonstrated the specificity, practicability, and expansibility of the proposed strategy. This work paves a new avenue for the activity assays of multiplex enzymes and promotes the development of mass spectrometric biosensing.

Smart Contact Lens with Dual-Sensing Platform for Monitoring Intraocular Pressure and Matrix Metalloproteinase-9

Contact lenses have become a popular health-monitoring wearable device due to their direct contact with the eyes. By integrating biosensors into contact lenses, real-time and noninvasive diagnoses of various diseases can be realized. However, current contact lens sensors often require complex electronics, which may obstruct the user's vision or even damage the cornea. Moreover, most of the reported contact lens sensors can only detect one analyte. Therefore, an optical-based dual-functional smart contact lens sensor has been introduced to monitor intraocular pressure (IOP) and detect matrix metalloproteinase-9 (MMP-9), both of which are key biomarkers in many eye-related diseases such as glaucoma. Specifically, the elevated IOP is continuously monitored by applying an antiopal structure through color changes, without any complex electronics. Together with the peptide modified gold nanobowls (AuNBs) surface-enhanced Raman scattering (SERS) substrate, the quantitative analysis of MMP-9 at a low nanomolar range is achieved in real tear samples. The dual-sensing functions are thus demonstrated, providing a convenient, noninvasive, and potentially multifunctional sensing platform for monitoring health and diagnostic biomarkers in human tears.

In situ ratiometric SERS imaging of intracellular protease activity for subtype discrimination of human breast cancer

Accurate discrimination between different cells at the molecular level is of fundamental importance for disease diagnosis. Endogenous proteases are such molecular candidates for cancer cell subtype study. But in situ probing their activity in live cells remains challenging for surface-enhanced Raman scattering (SERS). Here, we present a sensitive ratio-type SERS nanoprobe for imaging of matrix metalloproteinase-2 (MMP-2) in different cancer cells subtypes. The nanoprobe contained three components: a plasmon-active gold nanoparticle as the SERS enhancing matrix, Raman dye rhodamine B (Rh B)-labelled substrate peptides as the specific MMP-2 recognizer, and 2-naphthalenethiol (2-NT) as the internal standard. MMP-2-responsive cleavage of peptides from the nanoprobe surface results in decrease or even disappearance of SERS emission of Rh B, which was ratioed over the emission of 2-NT for the quantification of MMP-2 activity. Both in-tube assay and in-cell imaging results show that the MMP-responsive nanoprobe can work and serve to differentiate the normal breast cells from the tumorous ones, to differentiate two breast cancer cell subtypes with a different degree of malignancy. We believe that this SERS nanoprobe could find a wide application in the fields of tumor biology and accurate disease diagnosis.

Emergence of Responsive Surface-Enhanced Raman Scattering Probes for Imaging Tumor-Associated Metabolites

As a core hallmark of cancer, metabolic reprogramming alters the metabolic networks of cancer cells to meet their insatiable appetite for energy and nutrient. Tumor-associated metabolites, the products of metabolic reprogramming, are valuable in evaluating tumor occurrence and progress timely and accurately because their concentration variations usually happen earlier than the aberrances demonstrated in tissue structure and function. As an optical spectroscopic technique, surface-enhanced Raman scattering (SERS) offers advantages in imaging tumor-associated metabolites, including ultrahigh sensitivity, high specificity, multiplexing capacity, and uncompromised signal intensity. This review first highlights recent advances in the development of stimuli-responsive SERS probes. Then the mechanisms leading to the responsive SERS signal triggered by tumor metabolites are summarized. Furthermore, biomedical applications of these responsive SERS probes, such as the image-guided tumor surgery and liquid biopsy examination for tumor molecular typing, are summarized. Finally, the challenges and prospects of the responsive SERS probes for clinical translation are also discussed.

Interference-free SERS nanoprobes for labeling and imaging of MT1-MMP in breast cancer cells

The expression of membrane type-1 matrix metalloproteinase (MT1-MMP) in cancer cells is critical for understanding the development, invasion and metastasis of cancers. In this study, we devised an interference-free surface-enhanced Raman scattering (SERS) nanoprobe with high selectivity and specificity for MT1-MMP. The nanoprobe was comprised of silver core-silica shell nanoparticle with a Raman reporter tag (4-mercaptobenzonitrile) embedded in the interface. Moreover, the nitrile group in 4-mercaptobenzonitrile shows a unique characteristic peak in the Raman-silent region (1800-2800 cm^-1), which eliminates spectral overlapping or background interference in the Raman fingerprint region (500-1800 cm^-1). After surface modification with a targeting peptide, the nanoprobe allowed visualization and evaluation of MT1-MMP in breast cancer cells via SERS spectrometry. This interference-free, peptide-functionalized SERS nanoprobe is supposed to be conducive to early diagnosis and invasive assessment of cancer in clinical settings.

Electrochemical detection of matrix metalloproteinase-7 using an immunoassay on a methylene blue/2D MoS2/graphene oxide electrode

Methylene blue (MB) adsorption onto a two-dimensional molybdenum disulfide (2D MoS₂)/graphene oxide (GO) nanocomposite sitting on a screen-printed carbon electrode (SPCE) is used to develop a new sensitive label-free electrochemical immunosensor for the detection of matrix metalloproteinase-7 (MMP-7) cancer biomarkers. The 2D MoS₂/GO nanocomposite deposited onto an SPCE provides a large specific surface area, fast electron transfer, and exceptional electrical conductivity. Furthermore, MB adsorbed onto the 2D MoS₂/GO nanocomposite architecture can be used for signal amplification in electrochemical immunosensors. Moreover, an immunosensor platform was fabricated by the adsorption of anti-MMP-7 capture antibodies onto the MB/2D MoS₂/GO nanocomposite surface via electrostatic interactions for the detection of the MMP-7 immunocomplex. Under optimum conditions, the label-free immunosensor exhibits a decrease in the current response for MB corresponding to the MMP-7 concentration. The sensor affords a linear logarithmic range of 0.010-75 ng mL^-1 with a limit of detection (LOD) of 0.007 ng mL^-1. The developed electrochemical immunosensor provides high selectivity, good reproducibility, and excellent stability. Furthermore, the proposed immunosensor can be applied for the detection of MMP-7 in human serum samples with good recovery. Thus, this device can be applied for the early clinical diagnosis of pancreatic and colorectal cancers.

Geometrically encoded SERS nanobarcodes for the logical detection of nasopharyngeal carcinoma-related progression biomarkers

The limited availability of nasopharyngeal carcinoma-related progression biomarker array kits that offer physicians comprehensive information is disadvantageous for monitoring cancer progression. To develop a biomarker array kit, systematic identification and differentiation of a large number of distinct molecular surface-enhanced Raman scattering (SERS) reporters with high spectral temporal resolution is a major challenge. To address this unmet need, we use the chemistry of metal carbonyls to construct a series of unique SERS reporters with the potential to provide logical and highly multiplex information during testing. In this study, we report that geometric control over metal carbonyls on nanotags can produce 14 distinct barcodes that can be decoded unambiguously using commercial Raman spectroscopy. These metal carbonyl nanobarcodes are tested on human blood samples and show strong sensitivity (0.07 ng/mL limit of detection, average CV of 6.1% and >92% degree of recovery) and multiplexing capabilities for MMPs.

Biosensors and bioassays for determination of matrix metalloproteinases: state of the art and recent advances

Matrix metalloproteinases (MMPs) are closely associated with various physiological and pathological processes, and have been regarded as potential biomarkers for severe diseases including cancer. Accurate determination of MMPs would advance our understanding of their roles in disease progression, and is of great significance for disease diagnosis, treatment and prognosis. In this review, we present a comprehensive overview of the developed bioassays/biosensors for detection of MMPs, and highlight the recent advancement in nanomaterial-based immunoassays for MMP abundance measurements and nanomaterial-based biosensors for MMP activity determination. Enzyme-linked immunosorbent assay (ELISA)-based immunoassays provide information about total levels of MMPs with high specificity and sensitivity, while target-based biosensors measure the amounts of active MMPs, and allow imaging of MMP activities in vivo. For multiplex and high-throughput analysis of MMPs, microfluidics and microarray-based assays are described. Additionally, we put forward the existing challenges and future prospects from our perspective.

Peptide-Mediated Liposome Fusion as a Tool for the Detection of Matrix Metalloproteinases

Biological cells continue to inspire the development of technologies toward rapid, sensitive, and selective detection of analytes. Membrane fusion is a key biological event in living cells that involves a highly selective recognition mechanism controlled by different functional proteins. Herein, liposome-liposome fusion mediated by coiled-coil forming peptides JR2EC and JR2KC to mimic biological membrane fusion is reported. The liposome fusion event is monitored through fluorescence generation and this mechanism forms the basis of a detection assay for matrix metalloproteinases (MMPs), which are key homeostatic proteases. Using this approach, a limit of detection of 0.35 µg mL^-1 MMP-7 in biological samples is obtained, and this assay does not require washing, separation, or amplification steps. The developed tool could be extended for the detection of other proteolytic enzymes of the MMP family (diagnostic or prognostic markers) and has the potential for screening of peptide libraries against a target of interest.

A novel urine analysis technique combining affinity chromatography with Au nanoparticle based surface enhanced Raman spectroscopy for potential applications in non-invasive cancer screening

Modified nucleoside in urine samples is one of the most common biomarkers for cancer screening. Therefore, we developed a novel detection method for modified nucleoside detection in human urine. In this work, the modified nucleoside from real cancer patient's urine samples was first separated and purified using the affinity chromatography (AC) technology relying on its specific adsorption capacity. Then, surface-enhanced Raman spectroscopy (SERS) technology with the capability of single molecular detection was used to sensitively characterize the biomolecular features of modified nucleoside. A total of 141 high-quality SERS spectra of urinary modified nucleoside can be obtained from 50 gastric cancer patients and 43 breast cancer patients, as well as 48 healthy volunteers. Using principal component analysis combined with linear discriminant analysis (PCA-LDA), the diagnostic sensitivities for identifying gastric cancer vs normal, breast cancer vs normal, gastric cancer vs breast cancer were 84.0%, 76.7% and 82.0%, respectively, and the corresponding diagnostic specificities for each combination were 95.8%, 87.5% and 90.7%, respectively. These results show that this novel method based on urinary modified nucleoside detection combining AC and SERS technologies holds promising potential for developing a specific, non-invasive and label-free tool for cancer screening.

Recent Progress on Liquid Biopsy Analysis using Surface-Enhanced Raman Spectroscopy

Traditional tissue biopsy is limited in understanding heterogeneity and dynamic evolution of tumors. Instead, analyzing circulating cancer markers in various body fluids, commonly referred to as "liquid biopsy", has recently attracted remarkable interest for their great potential to be applied in non-invasive early cancer screening, tumor progression monitoring and therapy response assessment. Among the various approaches developed for liquid biopsy analysis, surface-enhanced Raman spectroscopy (SERS) has emerged as one of the most powerful techniques based on its high sensitivity, specificity, tremendous spectral multiplexing capacity for simultaneous target detection, as well as its unique capability for obtaining intrinsic fingerprint spectra of biomolecules. In this review, we will first briefly explain the mechanism of SERS, and then introduce recently reported SERS-based techniques for detection of circulating cancer markers including circulating tumor cells, exosomes, circulating tumor DNAs, microRNAs and cancer-related proteins. Cancer diagnosis based on SERS analysis of bulk body fluids will also be included. In the end, we will summarize the "state of the art" technologies of SERS-based platforms and discuss the challenges of translating them into clinical settings.

Superhydrophobic silver film as a SERS substrate for the detection of uric acid and creatinine

Superhydrophobic silver films were fabricated by silver-mirror reaction and surface functionalization with thiol. The thiol-functionalization significantly improved the hydrophobic property of the Ag films (AFS), and their contact angle values slightly increased with the extension of a thiol alkyl chain, reaching about 160°. The surface-enhanced Raman scattering (SERS) detection capacity of these films were investigated, and AFS-Dodec showed the best substrate for R6G molecule detection with the concentration limit of 10^-11 M. AFS functionalized with dodecanethiol (AFS-Dodec) was applied for the SERS detection of uric acid and creatinine, it exhibited good linear dependence relationship between the Raman intensity and analyte concentration in the concentration range of 5~1000 μM.

Multifunctional paper strip based on GO-veiled Ag nanoparticles with highly SERS sensitive and deliverable properties for high-performance molecular detection

The development of paper-based SERS substrates that can allow multi-component detection in real-word scenarios is of great value for applications in molecule detection under complex conditions. Here, a multifunctional SERS-based paper sensing substrate has been developed through the uniform patterning of high-density arrays of GO-isolated Ag nanoparticles on the hydrophilic porous cellulose paper strip (GO@AgNP@paper). Wet-chemical synthesis was used to provide the cover of SERS hot spots on any part of the paper, not just limited surface deposition. In virtue of the inherent ability of paper to deliver analytes by the capillary force, the detection ability of the GO@AgNP@paper substrate was greatly promoted, allowing as low as 10^-19M R6G detection from microliter-volume (50 μL) samples. For the components with different polarity, the paper substrate can be used as an all-in-one machine to achieve the integration of separation and high-sensitive detection for ultralow mixture components, which improves the practical application value of SERS-based paper devices.

Optical Interference-Free Surface-Enhanced Raman Scattering CO-Nanotags for Logical Multiplex Detection of Vascular Disease-Related Biomarkers

Matrix metalloproteinases (MMPs), specifically MMP-2, MMP-7, and MMP-9, have been discovered to be linked to many forms of vascular diseases such as stroke, and their detection is crucial to facilitate clinical diagnosis. In this work, we prepared a class of optical interference-free SERS nanotags (CO-nanotags) that can be used for the purpose of multiplex sensing of different MMPs. Multiplex detection with the absence of cross-talk was achieved by using CO-nanotags with individual tunable intrinsic Raman shifts of CO in the 1800-2200 cm^-1 region determined by the metal core and ligands of the metal carbonyl complex. Boolean logic was used as well to simultaneously probe for two proteolytic inputs. Such nanotags offer the advantages of convenient detection of target nanotags and high sensitivity as validated in the ischemia rat model.

Investigation of apoptotic events at molecular level induced by SERS guided targeted theranostic nanoprobe

Herein, we have examined distinctive structural and functional variations of cellular components during apoptotic cell death induced by a targeted theranostic nanoprobe, MMP-SQ@GNR@LAH-DOX, which acted as a SERS "on/off" probe in the presence of a MMP protease and executed synergistic photothermal chemotherapy, as reflected by the SERS fingerprinting, corresponding to the phosphodiester backbone of DNA.