A nanoporous palladium(II) bridged coordination polymer acting as a peroxidase mimic in a method for visual detection of glucose in tear and saliva

A Nanotechnology-Based Approach to Biosensor Application in Current Diabetes Management Practices

Diabetes mellitus is linked to both short-term and long-term health problems. Therefore, its detection at a very basic stage is of utmost importance. Research institutes and medical organizations are increasingly using cost-effective biosensors to monitor human biological processes and provide precise health diagnoses. Biosensors aid in accurate diabetes diagnosis and monitoring for efficient treatment and management. Recent attention to nanotechnology in the fast-evolving area of biosensing has facilitated the advancement of new sensors and sensing processes and improved the performance and sensitivity of current biosensors. Nanotechnology biosensors detect disease and track therapy response. Clinically efficient biosensors are user-friendly, efficient, cheap, and scalable in nanomaterial-based production processes and thus can transform diabetes outcomes. This article is more focused on biosensors and their substantial medical applications. The highlights of the article consist of the different types of biosensing units, the role of biosensors in diabetes, the evolution of glucose sensors, and printed biosensors and biosensing systems. Later on, we were engrossed in the glucose sensors based on biofluids, employing minimally invasive, invasive, and noninvasive technologies to find out the impact of nanotechnology on the biosensors to produce a novel device as a nano-biosensor. In this approach, this article documents major advances in nanotechnology-based biosensors for medical applications, as well as the hurdles they must overcome in clinical practice.

Recent Advancement in Biofluid-Based Glucose Sensors Using Invasive, Minimally Invasive, and Non-Invasive Technologies: A Review

Biosensors have potentially revolutionized the biomedical field. Their portability, cost-effectiveness, and ease of operation have made the market for these biosensors to grow rapidly. Diabetes mellitus is the condition of having high glucose content in the body, and it has become one of the very common conditions that is leading to deaths worldwide. Although it still has no cure or prevention, if monitored and treated with appropriate medication, the complications can be hindered and mitigated. Glucose content in the body can be detected using various biological fluids, namely blood, sweat, urine, interstitial fluids, tears, breath, and saliva. In the past decade, there has been an influx of potential biosensor technologies for continuous glucose level estimation. This literature review provides a comprehensive update on the recent advances in the field of biofluid-based sensors for glucose level detection in terms of methods, methodology and materials used.

Nanosensors for Visual Detection of Glucose in Biofluids: Are We Ready for Instrument-Free Home-Testing?

Making frequent large-scale screenings for several diseases economically affordable would represent a real breakthrough in healthcare. One of the most promising routes to pursue such an objective is developing rapid, non-invasive, and cost-effective home-testing devices. As a first step toward a diagnostic revolution, glycemia self-monitoring represents a solid base to start exploring new diagnostic strategies. Glucose self-monitoring is improving people's life quality in recent years; however, current approaches still present vast room for improvement. In most cases, they still involve invasive sampling processes (i.e., finger-prick), quite discomforting for frequent measurements, or implantable devices which are costly and commonly dedicated to selected chronic patients, thus precluding large-scale monitoring. Thanks to their unique physicochemical properties, nanoparticles hold great promises for the development of rapid colorimetric devices. Here, we overview and analyze the main instrument-free nanosensing strategies reported so far for glucose detection, highlighting their advantages/disadvantages in view of their implementation as cost-effective rapid home-testing devices, including the potential use of alternative non-invasive biofluids as samples sources.

Ultrathin PdCu alloy nanosheet-assembled 3D nanoflowers with high peroxidase-like activity toward colorimetric glucose detection

Enzyme-mimetic properties of nanomaterials can be efficiently tuned by controlling their size, composition, and structure. Here, ultrathin PdCu alloy nanosheet-assembled three-dimensional (3D) nanoflowers (Pd₁Cu_x NAFs) with tunable surface composition are obtained via a generalized strategy. In presence of H₂O₂, the as-synthesized Pd₁Cu_x NAFs can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to the oxidized form of TMB (oxTMB) with a characteristic absorption peak at 652 nm. Interestingly, Pd₁Cu_x NAFs show obviously composition-dependent peroxidase-like catalytic activities because of the synergistic interaction of nanoalloy. Additionally, different from 2D Pd nanosheets, the distinctive 3D superstructures are featured with rich approachable sites and proper layer spacing, which are in favor of fast mass transport and electron transfers during the catalytic process. Among the studied Pd₁Cu_x NAFs, the Pd₁Cu_1.7 NAFs show the highest enzyme-like activities and can be successfully applied for the colorimetric detection of glucose with a low detection limit of 2.93 ± 0.53 μM. This work provides an efficient avenue to fabricate PdCu NAF nanozymes in biosensing toward glucose detection. Two-dimensional (2D) PdCu ultrathin nanosheet-assembled 3D nanoflowers (Pd₁Cu_x NAFs) with tunable surface composition exhibit substantially enhanced intrinsic peroxidase-like catalytic activities. The Pd₁Cu_1.7 NAFs are successfully used as peroxidase mimic catalyst for the colorimetric detection of glucose with low detection limit of 2.93 μM.

Tunable Polymeric Scaffolds for Enzyme Immobilization

The number of methodologies for the immobilization of enzymes using polymeric supports is continuously growing due to the developments in the fields of biotechnology, polymer chemistry, and nanotechnology in the last years. Despite being excellent catalysts, enzymes are very sensitive molecules and can undergo denaturation beyond their natural environment. For overcoming this issue, polymer chemistry offers a wealth of opportunities for the successful combination of enzymes with versatile natural or synthetic polymers. The fabrication of functional, stable, and robust biocatalytic hybrid materials (nanoparticles, capsules, hydrogels, or films) has been proven advantageous for several applications such as biomedicine, organic synthesis, biosensing, and bioremediation. In this review, supported with recent examples of enzyme-protein hybrids, we provide an overview of the methods used to combine both macromolecules, as well as the future directions and the main challenges that are currently being tackled in this field.

Ultrasensitive Poly(boric acid) Hydrogel-Coated Quartz Crystal Microbalance Sensor by Using UV Pressing-Assisted Polymerization for Saliva Glucose Monitoring

Quartz crystal microbalance (QCM) has attracted extensive attention in the field of biological analysis and detection because of its high sensitivity, fast response, real-time measurement, good operability, and low-cost production. However, to detect the trace amounts of small molecules, such as low-concentration saliva glucose under physiological conditions, is still a major challenge. Herein, the surface of a QCM chip was coated with a poly(boric acid)-based hydrogel using UV pressing-assisted polymerization to obtain a simple device for glucose detection. The designed QCM sensor shows a record-low detection limit of glucose (3 mg/L at pH 7.5), which is ∼30 times lower than that of sensors fabricated by conventional surface initiation-spin coating. The outperformance of the poly(boric acid) hydrogel-coated QCM sensor is probably due to the uniform and compact microstructure, as well as the presence of sufficient glucose-binding sites resulting from the hydrogel coating generated by UV pressing-assisted polymerization. This method provides an important solution to detect the trace amounts of small organic molecules or ions and has the potential to push forward the practical applications of QCM sensors.

Polyethyleneimine-Stabilized Platinum Nanoparticles as Peroxidase Mimic for Colorimetric Detection of Glucose

Colorimetric detection of glucose using enzyme-mimic nanoparticles (NPs) has been drawing great attention. However, many NPs lack good stability in solution, which results in reduced color change of substrates in colorimetric detection. Liner soluble macromolecules with high cationic density may be suitable candidates for the stabilization of NPs. Herein, we prepared polyethyleneimine-stabilized platinum NPs (Pt n -PEI NPs) for colorimetric detection of glucose. The platinum NPs (Pt NPs) used in this system had small size (from 3.21 to 3.70 nm) and narrow size distribution. Pt50-PEI NPs had high stability within one week with a hydrodynamic size of ∼25 nm and slightly positive zeta potential. Pt50-PEI NPs-catalyzed oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2, generating blue oxidized TMB (oxTMB), which indicated the peroxidase-like property of Pt50-PEI NPs. The optimal condition for this reaction was pH = 4.0 at 30 °C. More importantly, Pt50-PEI NPs were successfully used to detect glucose concentration by a colorimetric method with high selectivity. The established method had a linear concentration range from 10 to 5000 μM with a detection limit of 4.2 μM. For example, the concentration of glucose in saliva was tested to be 0.15 mM using our method. The high stability of Pt50-PEI NPs enhanced the high accessibility of the active center of Pt NPs for substrates and consequent excellent catalytic property. This established method has great potential to be used in various applications for glucose detection in the future.

Tunable hierarchical surfaces of CuO derived from metal–organic frameworks for non-enzymatic glucose sensing

A facile thermal treatment is conducted to prepare nanosphere stacking CuO derived from Cu-MOF, which achieves good glucose sensing performance and is expected to be effective for developing non-enzyme and non-invasive glucose sensors.

Nanonetwork of Coordination Polymer AHMT-Ag for the Effective and Broad Spectrum Detection of 6-Mercaptopurine in Urine and Blood Serum

Nanocrystalline coordination polymers (NCCPs) have been considered as an incredible electrochemical sensor for the effective detection of biologically dynamic drug 6-mercaptopurine (6-MP). In the present report, a significantly stable infinite arrayed coordination polymeric network was self-assembled via metal with efficient organic tecton 4-amino-3-hydrazino-5-mercapto-1,2,4,-triazole (AHMT) in which silver(I) ions are coordinated by AHMT via hydrazino and exocyclic thiol linkage to form AHMT-Ag NCCP. An efficient and highly sensitive detection of 6-MP is attained owing to eminent electron channeling via polymeric nanocrystallite pores. An effective charge transfer leads to an interface of the AHMT-Ag nano-pores and electrolyte anchored electrode via π-π electron coupling and hydrophobic interaction. The voltammogram exposes acute redox behavior of 6-MP and discloses an impeccable illustration for the AHMT-Ag facilitated oxidation of 6-MP. This unique signature was applied in voltammetric detection of 6-MP in blood serum, human urine, and pharmaceutical formulation (tablet) by a considerable high sensitivity of 0.074, 0.058, and 0.036 μA/μM and a detection limit of 87, 97, and 37 nM, respectively. Thus, the prepared AHMT-Ag NCCP can provide a valuable platform for fabrication of highly sensitive electrochemical devices to assay biologically essential drug molecules.

Electrochemiluminescence resonance energy transfer between methylene blue and Ru(bpy)32+-doped silica nanoparticles and its application in the “turn-on” detection of glucose

The ECL donor Ru(bpy)₃²⁺-doped silica nanoparticles and acceptor methylene blue were applied in the electrochemiluminescence resonance energy transfer-based detection of glucose.

Colorimetric determination of glucose in solution and via the use of a paper strip by exploiting the peroxidase and oxidase mimicking activity of bimetallic Cu-Pd nanoparticles deposited on reduced graphene oxide, graphitic carbon nitride, or MoS2 nanosheets

This work describes the preparation of bimetallic Cu-Pd nanoparticles (NPs) on supports like reduced graphene oxide (rGO), graphitic carbon nitride (g-C₃N₄) and MoS₂ sheets with a size of <10 nm. rGO is found to be the best support for synthesizing Cu-Pd NPs with controlled shape, size and oxidation state. The Cu-Pd/rGO nanocomposite also demonstrated the best peroxidase and oxidase mimicking activity compared to Cu-Pd/g-C₃N₄ and Cu-Pd/MoS₂ nanocomposites. The peroxidase mimicking activity of Cu-Pd/rGO was investigated in more detail, and a glucose oxidase (GOx) based glucose sensor was constructed that is based on the enzymatic formation of H₂O₂ and the Cu-Pd NPs-assisted oxidation of tetramethylbenzidine by H₂O₂ to give a blue-green coloration with absorption maxima at 652 nm. The assay has a 0.29 μM detection limit and a detection range that extends from 0.2 to 50 μM. The method was applied to the determination of glucose in diluted serum samples, and results compared well to those acquired with a clinical analyzer. The method also was applied in a colorimetric paper-based test stripe that can detect glucose within 10 min. Graphical abstract Schematic representation of a sensitive colorimetric glucose assay based on bimetallic Cu-Pd nanoparticles supported on 2D nanosheets, and construction of a paper based device for rapid glucose detection.

Enhanced glucose detection using dendrimer encapsulated gold nanoparticles benefiting from their zwitterionic surface

The application of ultrasmall gold nanoparticles as enzyme mimics has been drawing great attention. Herein, we developed zwitterionic dendrimer encapsulated gold nanoparticles (Au-G5MC NPs) for highly sensitive and simple colorimetric detection of glucose. Au-G5MC NPs showed peroxidase-like property, which could efficiently catalyze oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H₂O₂, producing a blue color product (oxTMB). This peroxidase-like reaction follows a typical Michaelis-Menten kinetics. The K_m towards TMB exhibited a lower value (0.194 mM) than that of horseradish peroxidase (HRP, 0.434 mM). Furthermore, the peroxidase-like properties of Au-G5MC NPs enable colorimetric detection of the concentration of glucose with high selectivity. The linear concentration range of this method was from 14 μM to 166 μM with the detection limit down to 3.8 μM. More importantly, the detection was not interfered by proteins due to the single zwitterionic layer on the Au-G5MC NPs surface. These excellent properties are attributed to the ultrasmall size of gold nanoparticles and high stability of Au-G5MC NPs in complex medium. This catalytic system might have great potential applications for glucose detection in medical diagnostics and biochemistry in the future.