Tear-based MMP-9 detection: A rapid antigen test for ocular inflammatory disorders using vanadium disulfide nanowires assisted chemi-resistive biosensor

A sensitive, non-invasive, and biomarker detection in tear fluids for inflammation in potentially blinding eye diseases could be of great significance as a rapid diagnostic tool for quick clinical decisions. In this work, we propose a tear-based MMP-9 antigen testing platform using hydrothermally synthesized vanadium disulfide nanowires. Also, various factors contributing to baseline drifts of the chemiresistive sensor including nanowire coverage on the interdigitated microelectrode of the sensor, sensor response duration, and effect of MMP-9 protein in different matrix solutions were identified. The drifts on the sensor baseline due to nanowire coverage on the sensor were corrected using substrate thermal treatment providing a more uniform distribution of nanowires on the electrode which brought the baseline drift to 18% (coefficient of variations, CV = 18%). This biosensor exhibited sub-femto level limits of detection (LODs) of 0.1344 fg/mL (0.4933 fmoL/l) and 0.2746 fg/mL (1.008 fmoL/l) in 10 mM phosphate buffer saline (PBS) and artificial tear solution, respectively. For a practical tear MMP-9 detection, the proposed biosensor response was validated with multiplex ELISA using tear samples from five healthy controls which showed excellent precision. This label-free and non-invasive platform can serve as an efficient diagnostic tool for the early detection and monitoring of various ocular inflammatory diseases.

In situ quantitative measurements on MMP-9 activity in single living cells by single molecule fluorescence correlation spectroscopy

Matrix metalloproteinase-9 (MMP-9) plays an important role in tumor progression. It is of great significance to establish a sensitive in situ assay strategy for MMP-9 activity in single living cells. Here a novel in situ single molecule spectroscopy method based on the fluorescence correlation spectroscopy (FCS) technique was proposed for measuring the MMP-9 activity at different locations within single living cells, using a fluorescent specific peptide and a reference dye as dual probes. The measurement principle is based on the decrease of the ratiometric translational diffusion time of dual probes in the detection volume due to the peptide cleavage caused by MMP-9. The peptide probe was designed to be composed of an MMP-9 cleavage and cell-penetrating peptide sequence that was labeled with a fluorophore and conjugated with a streptavidin (SAV) molecule. The ratiometric translational diffusion time was used as the measurement parameter to eliminate the effect of intracellular uncertain viscosity. The linear relationship between the ratiometric diffusion time and MMP-9 activity was established, and applied to the determination of enzymatic activity in cell lysates as well as the evaluation of the inhibitory effects of different inhibitors on MMP-9. More importantly, the method was successfully used to dynamically determine MMP-9 activity in single living cells or under the stimulation with phorbol 12-myristate 13-acetate (PMA) and inhibitors.

Composing On-Program Triggers and On-Demand Stimuli into Biosensor Drug Carriers in Drug Delivery Systems for Programmable Arthritis Therapy

Medication in arthritis therapies is complex because the inflammatory progression of rheumatoid arthritis (RA) and osteoarthritis (OA) is intertwined and influenced by one another. To address this problem, drug delivery systems (DDS) are composed of four independent exogenous triggers and four dependent endogenous stimuli that are controlled on program and induced on demand, respectively. However, the relationships between the mechanisms of endogenous stimuli and exogenous triggers with pathological alterations remain unclear, which results in a major obstacle in terms of clinical translation. Thus, the rationale for designing a guidance system for these mechanisms via their key irritant biosensors is in high demand. Many approaches have been applied, although successful clinical translations are still rare. Through this review, the status quo in historical development is highlighted in order to discuss the unsolved clinical difficulties such as infiltration, efficacy, drug clearance, and target localisation. Herein, we summarise and discuss the rational compositions of exogenous triggers and endogenous stimuli for programmable therapy. This advanced active pharmaceutical ingredient (API) implanted dose allows for several releases by remote controls for endogenous stimuli during lesion infections. This solves the multiple implantation and local toxic accumulation problems by using these flexible desired releases at the specified sites for arthritis therapies.

Enzymatic cleavage of specific dipeptide conjugated with ferrocene as a flexible ultra-sensitive and fast voltammetric assay of matrix metalloproteinase-9 considered a prognostic cancer biomarker in plasma samples

Studies over the last decade have shown that matrix metalloproteinases (MMPs) play a key role in the growth and metastasis of cancer. This zinc-dependent family of endopeptidases is crucial for the degradation of extracellular matrix (ECM), as well as serves as important ECM transducers which have been recognized as early biomarkers for both cancer diagnosis and treatment. In this study, we designed a new type of voltammetric biosensor, composed of a glycine-methionine dipeptide conjugated covalently to ferrocene (Gly-Met-Fc), for fast and ultrasensitive detection of the active form of MMP-9 in plasma samples. The detection was based on specific enzymatic cleavage of the Gly-Met peptide bond, which was monitored by voltammetry and gravimetry measurements. The ferrocene units act as voltammetric visualizers for the detection process. The cysteamine layer directly anchored to the gold surface ensured that the packing density of Gly-Met-Fc in the receptor layer was appropriate for the sensitive detection of MMP-9 in its active form. The developed biosensor was characterized by the widest analytical range (2.0·10^-6 - 5.0 μg⋅mL^-1) and low detection limit (0.04 pg⋅mL^-1). Another valuable feature of the proposed biosensor is that it can be applied directly to the plasma samples without any additional preparation step and thus speeds up the analysis.

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.