Biodegradable and Flexible Thermoplastic Composite Graphite Electrodes: A Promising Platform for Inexpensive and Sensitive Electrochemical Detection of Creatine Kinase at the Point-of-Care.

Acute myocardial infarction (AMI) is the main cause of death worldwide, and the time of diagnosis is decisive for the effectiveness of the treatment of patients with AMI. Creatine kinase-myocardial band (CK-MB) has a predominance and high affinity with myocardial tissue, making it considered one of the main biomarkers for the diagnosis of AMI. In this work, we report a novel biodegradable composite material based on a polymer blend of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and Poly(butylene adipate-co-terephthalate) (PHBV:Ecoflex) and graphite microparticles for sensitive and selective electrochemical detection of CK-MB. The morphological and physicochemical characterizations of the thermoplastic composite material revealed a homogeneous and synergistic distribution of the graphite microparticles through the blend structure, providing low defects and high electrical conductivity with high electron transfer kinetics (k0 = 3.54 × 10-3 cm s-1) features with adequate flexibility for point-of-care applications. The portable and disposable devices were applied to detect CK-MB using the electrochemical impedance spectroscopy (EIS) technique in a relevant clinical concentration ranging from 5.0 ng mL-1 to 100.0 ng mL-1 and presented a limit of detection of 0.26 ng mL-1 CK-MB. The selectivity of the sensor was confirmed by testing the potential interference of major biomolecules found in biofluids and other relevant macromolecules. The accuracy and robustness were assessed by addition and recovery protocol in urine and saliva samples without sample pretreatment and demonstrated the potential of our method for rapid and decentralized tests of AMI. In addition, the study of the thermal, biological, and photodegradation of the devices after being used was also carried out, aiming at the disposal of the material more sustainably.

Improvement of UV stability of thermoplastic starch matrix by addition of selected lignin fraction - Photooxidative degradation.

This paper examines the additivation of thermoplastic starch (TPS) matrix by selected fractions of kraft lignin (KL) and correlates its structure-performance when exposed to photooxidative degradation. KL from Eucalyptus urograndis wood was refined by a sequential fractionation process in ethyl acetate (EtOAc). Films were prepared by mixing lignin fractions as additive in TPS matrix by casting and pressing. The lignin employed were KL, fraction of KL insoluble in EtOAc (INS) and fraction of KL soluble in EtOAc (SOL). The samples were exposed to accelerated aging with Ultraviolet-C light (UV-C) for 432 h. Structural changes were measured by FTIR (Fourier-Transform Infrared) spectra. Thermal properties, such as melting enthalpy, glass transition temperature and thermal decomposition, were evaluated by DSC (Differential Scanning Calorimetry) and TG (Thermogravimetry). Morphology of the films was obtained by SEM (Scanning Electron Microscopy). Surface property of wettability was measured by contact angle. Mechanical properties were explored before and after exposure to UV-C light. It was observed that the least photodegraded films were those resulting from the addition of the lignin fraction with higher phenolic hydroxyl group content. According to structural and morphological observations, the soluble fraction (TSOL) presented the highest photoprotection and stabilizing effect as an UV-C light blocker additive on TPS matrix.

Thermoplastic starch nanocomposites: sources, production and applications - a review.

The development of materials based on thermoplastic starch (TPS) is an excellent alternative to replace or reduce the use of petroleum-derived polymers. The abundance, renewable origin, biodegradability, biocompatibility, and low cost of starch are among the advantages related to the application of TPS compared to other thermoplastic biopolymers. However, through the literature review, it was possible to observe the need to improve some properties, to allow TPS to replace commonly used polyolefins. The studies reviewed achieved these modifications were achieved by using plasticizers, adjusting processing conditions, and incorporating fillers. In this sense, the addition of nanofillers proved to be the main modification strategy due to the large number of available nanofillers and the low charge concentration required for such improvement. The improvement can be seen in thermal, mechanical, electrical, optical, magnetic, antimicrobial, barrier, biocompatibility, cytotoxicity, solubility, and swelling properties. These modification strategies, the reviewed studies described the development of a wide range of materials. These are products with great potential for targeting different applications. Thus, this review addresses a wide range of essential aspects in developing of this type of nanocomposite. Covering from starch sources, processing routes, characterization methods, the properties of the obtained nanocomposites, to the various applications. Therefore, this review will provide an overview for everyone interested in working with TPS nanocomposites. Through a comprehensive review of the subject, which in most studies is done in a way directed to a specific area of study.

Improvements in thermal and mechanical properties of composites based on thermoplastic starch and Kraft Lignin.

Thermoplastic starch (TPS) is a widely studied biopolymer as an alternative to the use of conventional polymers. In this sense, the incorporation of fillers or reinforcements coming preferably from other substances of natural origin, can be an alternative to try to improve some mechanical and thermal properties of starch polymers. Thus, Kraft Lignin (KL), can be an excellent filler to be incorporated, since it presents mechanical and thermal properties and reduces the cost and weight of the final compounds. TPS films were prepared by casting using dimethyl sulfoxide (DMSO) as solvent and additives with 2, 4 and 8% KL. Characterization of TPS films and compositions with KL were carried out by Fourier-Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscope (SEM), Thermogravimetric Analysis (TGA), Dynamic Thermomechanical Analysis (DMTA), tensile testing and contact angle. Samples were also analyzed for biodegradation and for the ability to remove contaminants in water, Metil Orange (MO), by Ultraviolet-Visible Spectroscopy (UV-Vis). The FT-IR spectra of the films showed bands typical of functional groups derived from starch and lignin, with the intensity of these bands varying among the samples studied. Micrographs revealed slightly different morphologies among the films, but all showed irregular shapes with structures that appeared as plots. Increasing the percentage of KL led to an increase in contact angle values, showing a more hydrophobic behavior. In the TGA analysis, it was possible to observe a change in the main degradation event of the films for lower temperatures, especially of TPS - 4 and 8% KL compared to the TPS film. Films with KL had the peak of maximum degradation shifted to temperatures below the starch film, where the decrease in intensity of the main peak in the TPS - 4% KL and TPS - 8% KL samples demonstrates that there was less mass loss in the event. There was also in the percentage of residue as the addition of KL was increased The DMTA analyses allowed for the conclusion that presence of KL in TPS film allowed for an increase in its energy storage property, and that the loss modulus followed a decreasing order of storage modulus values to TPS - 8% KL from TPS. For the tensile strength property only TPS - 4% KL has significant improvement, and the elongation at break showed an increase for TPS - 4 and 8% KL compared to TPS. Samples showed a continuous and progressive biodegradation process, being completely biodegraded within 10 days. The monitoring of the ability to remove contaminants from water by UV-Vis, also showed promising results of compounds for this application. The best results were obtained, in most tests, for the TPS- 4% KL films.

Review of cellulose nanocrystals patents: preparation, composites and general applications.

This review attempts to visualize the actual impact of nanocellulose-based materials in different areas. A detailed search in recent patent databases on nanocellulose showed the importance of this material, as well as relevant topics concerning its technological preparations to obtain versatile new composites materials, and the applications of nanocellulose in different domains. At the present moment, the most common techniques for nanocellulose preparation were found to be acid and enzymatic procedures, oxidation, electrospinning, high pressure homogenization, and steam explosion processes. Concerning nanocellulose composites, several aspects were found in recent patents ranging from simple to complex structures with different properties. As unique materials, nanocellulose can be used in different areas of expertise, such as in biomedical and technical applications. This review is a useful tool for researchers to provide an update on nanocellulose patents in an expanding and interesting field of nanotechnology.