TiO₂ Nanotubes Alginate Hydrogel Scaffold for Rapid Sensing of Sweat Biomarkers: Lactate and Glucose

Abstract

Versatile sensing matrixes are essential for the development of enzyme-immobilized optical biosensors. A novel three-dimensional titanium dioxide nanotubes/alginate hydrogel scaffold is proposed for the detection of sweat biomarkers, lactate, and glucose in artificial sweat. Hydrothermally synthesized titanium dioxide nanotubes were introduced to the alginate polymeric matrix, followed by cross-linking nanocomposite with dicationic calcium ions to fabricate the scaffold platform. Rapid colorimetric detection (blue color optical signal) was carried out for both lactate and glucose biomarkers in artificial sweat at 4 and 6 min, respectively. The superhydrophilicity and the capillarity of the synthesized titanium dioxide nanotubes, when incorporated into the alginate matrix, facilitate the rapid transfer of the artificial sweat components throughout the sensor scaffold, decreasing the detection times. Moreover, the scaffold was integrated on a cellulose paper to demonstrate the adaptability of the material to other matrixes, obtaining fast and homogeneous colorimetric detection of lactate and glucose in the paper substrate when image analysis was performed. The properties of this new composite provide new avenues in the development of paper-based sensor devices. The biocompatibility, the efficient immobilization of biological enzymes/colorimetric assays, and the quick optical signal readout behavior of the titanium dioxide nanotubes/alginate hydrogel scaffolds provide a prospective opportunity for integration into wearable devices.

Alginate Bead Biosystem for the Determination of Lactate in Sweat Using Image Analysis

“…[22] fabricated alginate beads modified with an indicator of Co 2+ capable of effectively detecting Co 2+ in aqueous solutions as an environmental analysis tool. Recently, our group has developed an alginate/titanium dioxide nanotubes nanocomposite for the detection of lactate and glucose [26].…”

Shaping Macromolecules for Sensing Applications—From Polymer Hydrogels to Foldamers

“…Polymeric materials used for sensors are divided into natural hydrogels, derived from natural polymers, e.g., proteins (collagen [ 76 , 80 , 83 ], elastin [ 84 , 85 ], gelatin [ 86 , 87 , 88 ], albumin [ 29 , 89 ]), polysaccharides (hyaluronic acid [ 90 ], alginate [ 91 , 92 , 93 , 94 , 95 ], chitosan [ 82 , 96 , 97 , 98 , 99 , 100 , 101 ], cellulose [ 74 ]), and synthetic hydrogels [ 39 , 102 , 103 , 104 , 105 , 106 ], based on laboratory-made polymers. Hydrogels in sensing applications are often used as a hybrid material, blend of polymers or in composition with inorganic materials, e.g., graphene, graphene oxide, or silica [ 31 ].…”

“… LOD = 0.14 U/mL Linear range: 0.5–100 U/mL Selectivity among different ions (NaCl, KCl, MgSO 4 , CaCl 2 , small molecules (glutathione, glucose, glutamine and ascorbic acid), BSA, and enzymes (alkaline phosphatase, trypsin, papain). [ 90 ] Alginate crosslinked with Cu 2+ Fluorescence Immunoassay Alkaline phosphatase (ALP) LOD = 0.24 ng/mL (serum) Linear range: ~0–2 ng/mL Hepatis B surface antigen (HBsAg) Selectivity among Na + , K + , HAS, lysozyme, thrombin, glucose oxidase Gel-sol transition [ 91 ] Alginate-in-alginate with palladium tetracarboxyphenylporphyrin Optical Glucose (low O 2 ) Linear Range: 0.026–3.5 g/L Sensitivity: 97 ± 5.4 µs L/g (ambient O 2 ) Linear Range: 0.87–3.5 g/L; Sensitivity: 7.5 ± 1.3 µs L/g [ 92 ] Alginate-based microfibres with mesoporous polyester beads Optical pH of epidermis pH range: 4–9 (range for skin disorders and wounds variation) [ 94 ] Titanium oxide nanotubes/alginate hydrogel Colorimetric assay Biomarkers LOD = 0.069 mM (lactate) Linear ranges: 0.1–1.0 mM LOD = 0.044 mM (glucose) Linear range: 0.1–0.8 mM [ 95 ] Fluorescent chitosan Fluorescence Nitrocompounds, p-nitrophenol Nitrocompounds quench Fluorescence, LOD = 0.35–2.30 µM (2,4,6-trinitrophenol) LOD = 0.90–5.30 µM <...>…”

Fabrication, Property and Application of Calcium Alginate Fiber: A Review

“…Based on the ability to gel with metal ions, different alginate-based materials with various morphology were developed, such as the porous scaffold [ 9 , 10 , 11 ], hydrogel [ 12 , 13 ], fiber [ 14 , 15 , 16 ], nonwoven fabric [ 17 , 18 ], membrane [ 19 , 20 , 21 ], and so forth. The common way to fabricate the alginate-based materials includes ion cross-linking [ 22 ], microfluidic spinning technique [ 23 ], freeze-drying [ 24 ], wet spinning technology [ 25 ] and immersive rotary/centrifugal jet spinning technique [ 26 , 27 , 28 ].…”