In this work, starch-based porous cryogels with controlled mechanical and electrical properties were prepared for tissue engineering applications. The starch cryogels were formulated using kappa-carrageenan, poly(vinyl alcohol) (PVA), and styrylpyridinium-substituted PVA (SbQ) into the composite. A conductive cryogel was polymerized by chemical oxidation of 3,4-ethylenedioxythiophene (EDOT) using iron(III) p-toluenesulfonate as a strategy to control the electrical properties. The physical, thermal, and mechanical properties were evaluated for the obtained composites. Macro- and nanoscale results confirmed the capability of tuning the mechanical properties of the material by the addition of biopolymers in different contents. The presence of kappa-carrageenan significantly increased the storage modulus and decreased the damping effect in the formulations. The presence of PVA showed a plasticizing effect in the formulations, confirmed by the buffering effect and an increase in storage modulus. PVA-SBQ improved the mechanical properties by cross-linking. The addition of PEDOT increased the mechanical and electrical properties of the obtained materials.

In this work, the effect of iron(III) in the preparation of a conductive porous composite using a biomass waste-based starch template was evaluated. Biopolymers are obtained from natural sources, for instance, starch from potato waste, and its conversion into value-added products is highly significant in a circular economy. The biomass starch-based conductive cryogel was polymerized via chemical oxidation of 3,4-ethylenedioxythiophene (EDOT) using iron(III) p-toluenesulfonate as a strategy to functionalize porous biopolymers. Thermal, spectrophotometric, physical, and chemical properties of the starch template, starch/iron(III), and the conductive polymer composites were evaluated. The impedance data of the conductive polymer deposited onto the starch template confirmed that at a longer soaking time, the electrical performance of the composite was improved, slightly modifying its microstructure. The functionalization of porous cryogels and aerogels using polysaccharides as raw materials is of great interest for applications in electronic, environmental, and biological fields.

Recently, tissue engineering and regenerative medicine studies have evaluated smart biomaterials as implantable scaffolds and their interaction with cells for biomedical applications. Porous materials have been used in tissue engineering as synthetic extracellular matrices, promoting the attachment and migration of host cells to induce the in vitro regeneration of different tissues. Biomimetic 3D scaffold systems allow control over biophysical and biochemical cues, modulating the extracellular environment through mechanical, electrical, and biochemical stimulation of cells, driving their molecular reprogramming. In this review, first we outline the main advantages of using polysaccharides as raw materials for porous scaffolds, as well as the most common processing pathways to obtain the adequate textural properties, allowing the integration and attachment of cells. The second approach focuses on the tunable characteristics of the synthetic matrix, emphasizing the effect of their mechanical properties and the modification with conducting polymers in the cell response. The use and influence of polysaccharide-based porous materials as drug delivery systems for biochemical stimulation of cells is also described. Overall, engineered biomaterials are proposed as an effective strategy to improve in vitro tissue regeneration and future research directions of modified polysaccharide-based materials in the biomedical field are suggested.

This document reviews the design and fabrication process of electrodes in Costa Rica, to be use in electric cell-substrate stimulations and electrochemical impedance sensing up to 10 kHz. The effect of the electrode design (through electrode sensor area and passivation coating) on electrode was simulated and experimentally evaluated using electrochemical impedance spectroscopy (EIS) measurements. The high charge points in the electrode were minimize by passivation after the simulation. It was observed that the passivated area has an impedance contribution by minimizing parasite currents. The optimized design of electrode reported in this work will make it possible to probe the cell growth, adhesion and biological cell layers by reducing measurement artifacts and improving the quality of data. The self-made flexible electrodes may allow being use in cell culture studies and to measure in real-time the cellular properties during the in vitro study and by chemical modifications may be used in the charge molecules control release.

Smart conductive materials are developed in regenerative medicine to promote a controlled release profile of charged bioactive agents in the vicinity of implants. The incorporation and the active electrochemical release of the charged compounds into the organic conductive coating is achieved due to its intrinsic electrical properties. The anti-inflammatory drug dexamethasone was added during the polymerization, and its subsequent release at therapeutic doses was reached by electrical stimulation. In this work, a Poly (3,4-ethylenedioxythiophene): κ-carrageenan: dexamethasone film was prepared, and κ-carrageenan was incorporated to keep the electrochemical and physical stability of the electroactive matrix. The presence of κ-carrageenan and dexamethasone in the conductive film was confirmed by µ-Raman spectroscopy and their effect in the topographic was studied using profilometry. The dexamethasone release process was evaluated by cyclic voltammetry and High-Resolution mass spectrometry. In conclusion, κ-carrageenan as a doping agent improves the electrical properties of the conductive layer allowing the release of dexamethasone at therapeutic levels by electrochemical stimulation, providing a stable system to be used in organic bioelectronics systems.

Organic conductive polymers have been widely used as active layers in bioelectronic devices. In this work, a novel approach to entrap enzymes directly into the conductive active layer is described, using a polysaccharide as a surfactant. The surfactant allowed the electropolymerization from a micellar media and it acted as a doping agent in the conductive polymer. Gold nanotriangles were added to the matrix in order to enhance the enzymatic product quantification. The composition and oxidation state of the biocompatible conductive layer were confirmed by infrared spectrophotometric and Raman studies. Meanwhile, the gold nanotriangles presence, distribution and electrochemical activity were studied by transmission electron microscopy, atomic force microscopy, dynamic light scattering and cyclic voltammetry techniques. The inhibition of the enzyme, due to the presence of pesticides, was used to electrochemically quantify their concentration in real water samples. The concentration was confirmed by gas and liquid chromatography. Therefore, this novel composite active layer allows building a biosensor with suitable performance for an early warning in environmental control, especially in countries highly impacted by agricultural activities.

Infiltration into soils of pesticides used during agricultural production has led to the contamination of aquatic ecosystems due to their long persistence in the environment. Some pesticides (e.g. Chlorpyrifos) are inhibitors of cholinesterase enzyme activity and their presence in water samples can be indirectly detected by a decrease in enzymatic activity. Biosensors based on cholinesterase enzymes are an alternative for the sensitive detection of important contaminants in the environmental sector. Acetylcholinesterase enzyme (AChE) catalyzes the hydrolysis of acetylthiocholine (ATCh) to produce thiocholine (TCh). This feature can be employed to measure the decrease in AChE activity. The inhibitory characteristics of the AChE-Chlorpyrifos system have been studied through cyclic voltammetry, by evaluation of the oxidation of the thiol group, which corresponds to TCh production on platinum electrodes in the presence of an inhibitor. In the present study, enzymatic curves were obtained at different concentrations of substrate and inhibitor, which were then used to determine the enzymatic kinetics corresponding to a mixed inhibition type, with an inhibition constant (Ki) of (18.26 ± 0.01) μM. TCh electrochemical detection appears to be a promising option for the development of biosensors to identify and quantify pesticides present in the ecosystem.

Poly(3,4-ethylenedioxythiophene) (PEDOT) is synthesized through a micellar dispersion that allows incorporation of biomolecules into this conductive polymer layer. A PEDOTiK-carrageenan (κC) system was obtained by electrodeposition and it was compared with a standard PEDOT:sodium dodecyl sulfate electrode coat. The electrochemical behavior and the oxidation level after 1000 cycles were studied through cyclic voltammetry and μRaman spectroscopy. The oxidation ratio in the PEDOT increased while electrochemical activity decreased in both cases. Moreover, the PEDOT:κC system allowed the immobilization of the acetylcholinesterase enzyme, which retained its activity. The unique combination of properties is a key feature in the bioelectronics field.

espanolEn el presente trabajo se establece un protocolo para la inmovilizacion de la enzima acetilcolinesterasa (AChE), el cual puede ser utilizado para integrar dicho elemento biologico a un electrodo para la medicion de pesticidas. Se evalua una metodologia para la fijacion de la enzima en una matriz de poli(alcohol vinilico) (PVA), utilizando benzoato de sodio como agente entrecruzante. Esto se llevo a cabo por medio de la caracterizacion del proceso de entrecruzamiento del PVA, al irradiar con luz ultravioleta peliculas de este polimero a 5, 15, 30, 60, y 120 segundos. La formacion de la matriz se evidencio por medio de tecnicas como FTIR, DSC y TGA. De igual forma, se evaluo la actividad enzimatica de la enzima AChE soluble y atrapada en la matriz de PVA, por medio del valor de la velocidad inicial de reaccion. Se establecio que el tiempo optimo de entrecruzamiento del PVA es de 60 segundos de exposicion a luz ultravioleta. Se evidencia actividad enzimatica de la AChE atrapada en la matriz de PVA. EnglishIn this work, we have established a methodology for the immobilization of the acetyl cholin esterase (AChE) enzyme, which could be used for the development of biosensors to measure pesticides. It is evaluated a methodology to fix the acetyl cholin esterase (AChE) enzyme in a polyvinyl alcohol (PVA) matrix, using sodium benzoate as crosslinking agent. This was reached by irradiating PVA films for 5, 15, 30, 60, and 120 seconds with UV light and quantifying the crosslinking process. The matrix formation was studied using techniques as FITR, DSC and TGA. Moreover, the enzymatic activity of the soluble and trapped AChE enzyme was measured using the value of the initial reaction rate. The optimal time of crosslinking the PVA was found within 60 seconds of exposure to UV light. The enzymatic activity of the AChE trapped in the PVA matrix was verified.