An optical biosensor for the determination of cathepsin B as a cancer-associated enzyme using nanoporous anodic alumina modified with human serum albumin-thionine

Protease detection in the biosensor era: A review

Proteases have been proposed as potential biomarkers for several pathological conditions including cancers, multiple sclerosis and cardiovascular diseases, due to their ability to break down the components of extracellular matrix and basement membrane. The development of protease biosensors opened up the possibility to investigate the proteolytic activity of dysregulated proteases with higher efficiency over the traditional detection assays due to their quick detection capability, high sensitivity and selectivity, simple instrumentation and cost-effective fabrication processes. In contrast to the recently published review papers that primarily focused on one specific class of proteases or one specific detection method, this review article presents different optical and electrochemical detection methods that can be used to design biosensors for all major protease families. The benefits and drawbacks of various transducer techniques integrated into protease biosensing platforms are analyzed and compared. The main focus is on activity-based biosensors that use peptides as biorecognition elements. The effects of nanomaterials on biosensor performance are also discussed. This review should help readers to select the biosensor that best fits their needs, and contribute to the further development of this research field. Protease biosensors may allow better comprehension of protease overexperession and potentially enable novel devices for point-of-care testing.

Recent advances in the peptide-based biosensor designs

Biosensors have rapidly emerged as a high-sensitivity and convenient detection method. Among various types of biosensors, optical and electrochemical are the most commonly used. Conventionally, antibodies have been employed to ensure specific interaction between the transmission material and analytes. However, there has been increasing recognition of peptides as a promising recognition element for biosensor development in recent years. The use of peptides as recognition elements provides high level of specificity, sensitivity, and stability for the detection process. The combination of peptide designs and optical or electrochemical detection methods has significantly improved biosensor efficacy. These advancements present opportunities for developing biosensors with diverse functions that can be used to lay a strong scientific foundation for the development of personalized medicine and various other fields. This paper reviews the recent advancements in the development and application of peptide-based optical and electrochemical biosensors, as well as their prospects as a sensor type.

A highly sensitive NanoLuc-based protease biosensor for detecting apoptosis and SARS-CoV-2 infection

Proteases play critical roles in various biological processes, including apoptosis and viral infection. Several protease biosensors have been developed; however, obtaining a reliable signal from a very low level of endogenous protease activity remains a challenge. In this study, we developed a highly sensitive protease biosensor, named FlipNanoLuc, based on the Oplophorus gracilirostris NanoLuc luciferase. The flipped β-strand was restored by protease activation and cleavage, resulting in the reconstitution of luciferase and enzymatic activity. By making several modifications, such as introducing NanoBiT technology and CL1-PEST1 degradation tag, the FlipNanoLuc-based protease biosensor system achieved more than 500-fold luminescence increase in the corresponding protease-overexpressing cells. We demonstrated that the FlipNanoLuc-based caspase sensor can be utilized for the detection of staurosporine-induced apoptosis with sixfold increase in luminescence. Furthermore, we also demonstrated that the FlipNanoLuc-based coronavirus 3CL-protease sensor can be used to detect human coronavirus OC43 with tenfold increase in luminescence and severe acute respiratory syndrome-coronavirus-2 infections with 20-fold increase in luminescence by introducing the stem-loop 1 sequence to prevent the virus inducing global translational shutdown.

Symmetrically Controlled Design of Twin Alumina-Co Composite Thin Films

Self-assembled dual-working electrode electrolytic cells were designed to produce twin alumina-Co composite films with highly symmetrical microstructures using a deflected electric field-assisted alternating current electrodeposition method. The results show that the deposition current density, microstructure, and optical and magnetic properties of the twin composite films exhibit a high degree of symmetry. The distribution of magnetic Co particles in the alumina nanopores can be changed by adjusting the magnitude of the deflected electric field, resulting in a synchronous symmetrical change in the microstructure of the composite films, which enables the fine-tuning of the magneto-optical properties of the twin alumina-Co composite films at the microscopic scale. The current density distribution on the surface of the twin composite films along the direction of the deflected electric field was quantitatively analyzed by theoretical calculations and numerical simulations. The results show that the deposition current density gradually increases from 0.024 A/m2 in region C to 0.056 A/m2 in region A at 6 V deflection voltage. The saturation magnetization intensity gradually increases along the radial direction, which is 118, 130, and 150 kA/m, respectively

Nanochannel-based sensor for the detection of lead ions in traditional Chinese medicine

Lead ions (Pb2+) are used in the quality control of traditional Chinese medicine (TCM) preparations because they are highly toxic to human health. At present, sophisticated analytical instrumentation and complicated procedures for sample analysis are needed for the determination of Pb2+. Herein, a simple, fast, and sensitive peptide-modified nanochannel sensor to detect Pb2+ in TCM is reported, which is based on a Pb2+-specific peptide modified porous anodized aluminum membrane (PAAM). This peptide-based nanochannel clearly has the highest selectivity for Pb2+ when compared to other heavy metal ions, including As2+, Cd3+, Co2+, Cr2+, Cu2+, Fe3+, Hg2+, Mg2+, Mn2+, Ni2+, and Zn2+. Based on linear ranges from 0.01 to 0.16 μM and 10 to 100 μM, the detection limit was calculated to be 0.005 μM. Moreover, this peptide-based nanochannel sensor was successfully used to detect Pb2+ in complex TCM samples. In addition, when compared with the gold standard atomic absorption spectrophotometry (AAS) method, the recovery of the peptide-modified nanochannel sensor was between 87.7% and 116.8%. The experimental results prove that this new sensor is able to achieve accurate detection of Pb2+ in TCM samples. Thus, this sensor system could provide a simple assay for sensitive and selective detection of Pb2+ in TCM, thereby showing great potential in the practical application for the quality control of heavy metals in TCM.

Biosensors for the detection of respiratory viruses: A review

The recent events of outbreaks related to different respiratory viruses in the past few years, exponentiated by the pandemic caused by the coronavirus disease 2019 (COVID-19), reported worldwide caused by SARS-CoV-2, raised a concern and increased the search for more information on viruses-based diseases. The detection of the virus with high specificity and sensitivity plays an important role for an accurate diagnosis. Despite the many efforts to identify the SARS-CoV-2, the diagnosis still relays on expensive and time-consuming analysis. A fast and reliable alternative is the use of low-cost biosensor for in loco detection. This review gathers important contributions in the biosensor area regarding the most current respiratory viruses, presents the advances in the assembly of the devices and figures of merit. All information is useful for further biosensor development for the detection of respiratory viruses, such as for the new coronavirus.

Porous Aluminium Oxide Coating for the Development of Spectroscopic Ellipsometry Based Biosensor: Evaluation of Human Serum Albumin Adsorption

An electrochemically synthesised porous anodic aluminium oxide (pAAO) layer has been analysed by means of spectroscopic ellipsometry. The determined thickness of the formed pAAO layer obtained from spectroscopic ellipsometry measurements and modelling was 322.75 ± 0.12 nm. The radius of the nanopores estimated from SEM images was 39 ± 5 nm and the distance between nanopores was 107 ± 6 nm. The investigation of human serum albumin (HSA) adsorption on the pAAO coating showed that: (i) the protein concentration inside nanopores, depending on exposure time, approximately was from 200 up to 600 times higher than that determined in buffer solution; (ii) the initial phase of the adsorption process is slow (3.23 mg·cm−3·min−1) in comparison with the protein desorption rate (21.2 mg·cm−3·min−1) by means of pAAO layer washing; (iii) conventional washing with PBS solution and deionised water does not completely remove HSA molecules from pAAO pores and, therefore, the HSA concentration inside nanopores after 16 h of washing still remains almost 100 times higher than that present in PBS solution. Thus, due to such binding ability, HSA can be successfully used for the blocking of the remaining free surface, which is applied for the reduction in non-specific binding after the immobilisation of biorecognition molecules on the pAAO surface. It was determined that some desorption of HSA molecules from the pAAO layer occurred during the sensor’s surface washing step; however, HSA concentration inside the nanopores still remained rather high. These results recommend the continued application of pAAO in the development of biosensors.

Magnetic nanoparticle decorated anodic alumina nanotubes for fluorescent detection of cathepsin B

In this work, we present the process to provide anodic alumina nanotubes with magnetic responsivity based on magnetic nanoparticles. We demonstrate the possibility to cause the motion of these composite nanotubes under magnetic field, providing them with guided mobility. The obtained magnetic anodic alumina nanotubes are completely characterized and their potential to undergo selective and effective functionalization, and stimuli-responsive load release is demonstrated. For this purpose, protease-triggered release of fluorescent molecules loaded inside the magnetic anodic alumina nanotubes (MAANTs) by selective functionalization is performed. The inner walls of the MAANTs were selectively covered with protein padding of albumin-fluorescein isothiocyanate conjugate (FITC-BSA) through means of silanization. Protein functionalization was designed to undergo proteolytic hydrolysis in presence of cathepsin B- protease highly expressed during growth and initial stages of tumor metastasis - in order to cleave peptide bond of albumin and release fluorescent fragments of the protein. Proteolytic reaction with the enzyme is performed under acidic conditions. Presented arrangement is an exemplary combination of functionalities - which are vast - and of value for applications like drug delivery and biosensing applications.

Advances in Optical Biosensors and Sensors Using Nanoporous Anodic Alumina

This review paper focuses on recent progress in optical biosensors using self-ordered nanoporous anodic alumina. We present the fabrication of self-ordered nanoporous anodic alumina, surface functionalization, and optical sensor applications. We show that self-ordered nanoporous anodic alumina has good potential for use in the fabrication of antibody-based (immunosensor), aptamer-based (aptasensor), gene-based (genosensor), peptide-based, and enzyme-based optical biosensors. The fabricated optical biosensors presented high sensitivity and selectivity. In addition, we also showed that the performance of the biosensors and the self-ordered nanoporous anodic alumina can be used for assessing biomolecules, heavy ions, and gas molecules.