Abstract
Sensors are tools for detecting, recognizing, and recording signals from the surrounding environment. They provide measurable information on chemical or physical changes, and thus are widely used in diagnosis, environment monitoring, food quality checks, or process control. Polymers are versatile materials that find a broad range of applications in sensory devices for the biomedical sector and beyond. Sensory materials are expected to exhibit a measurable change of properties in the presence of an analyte or a stimulus, characterized by high sensitivity and selectivity of the signal. Signal parameters can be tuned by material features connected with the restriction of macromolecule shape by crosslinking or folding. Gels are crosslinked, three-dimensional networks that can form cavities of different sizes and forms, which can be adapted to trap particular analytes. A higher level of structural control can be achieved by foldamers, which are macromolecules that can attain well-defined conformation in solution. By increasing control over the three-dimensional structure, we can improve the selectivity of polymer materials, which is one of the crucial requirements for sensors. Here, we discuss various examples of polymer gels and foldamer-based sensor systems. We have classified and described applied polymer materials and used sensing techniques. Finally, we deliberated the necessity and potential of further exploration of the field towards the increased selectivity of sensory devices.
Highlights
Sensing is a very important division in applied sciences, present in several sectors such as diagnosis and treatment [1,2], environment monitoring [3], processes control [4], and food quality analysis [5]
The working electrode (WE) presents the electroconductive materials which are responsible for biorecognition event with the targeted species, causing the change of the electrochemical signal, recorded as impedance, current, or voltage
This pH-sensitive system showed remarkable photoluminescence characteristics in the near-neutral pH range of the gastrointestinal tract and can bypass the strongly acidic environment of the stomach, releasing loaded therapeutics in the intestine. These hydrogels showed cytocompatibility and non-toxicity in the cellular environment. These results demonstrated that such gelatin nanocomposite (GNC) can be a valuable candidate for in vivo imaging, biosensing applications, and the quantitative measurement of pH in the digestive system [88]
Summary
Sensing is a very important division in applied sciences, present in several sectors such as diagnosis and treatment [1,2], environment monitoring [3], processes control [4], and food quality analysis [5]. We can distinguish optical sensing (absorbance, reflectance, luminescence, fluorescence, index of refraction, opto-thermal and scattering effects); electrochemical sensing (voltammetry, amperometry, potentiometry and field-effect); mass sensing (piezoelectricity and surface acoustic wave effects); thermometric sensing (heat effects derived from chemical reaction or absorption); and radiation sensing (based on the absorbance of radioactive species) [11] Apart from this classification, sensors can be classified by their probe elements (such as polymer, ionophore, enzymes, antigens/antibodies, cell, protein and membrane receptors, tissues, oligonucleotides, specific ligands, etc.) and by the sensed analyte (such as glucose, DNA, enzymes, toxins, drugs, etc.). The foldamer-based sensors have been described in a separate section of this review article Another type of crosslinked polymer material widely applied in sensing is molecularly imprinted polymers [44]. We mention some recent advances in the field of gels, along with unsolved issues, and suggest possible solutions
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