Octacalcium Phosphate-Laden Hydrogels on 3D-Printed Titanium Biomaterials Improve Corrosion Resistance in Simulated Biological Media

The inflammatory-associated corrosion of metallic dental and orthopedic implants causes significant complications, which may result in the implant's failure. The corrosion resistance can be improved with coatings and surface treatments, but at the same time, it might affect the ability of metallic implants to undergo proper osteointegration. In this work, alginate hydrogels with and without octacalcium phosphate (OCP) were made on 3D-printed (patterned) titanium alloys (Ti Group 2 and Ti-Al-V Group 23) to enhance their anticorrosion properties in simulated normal, inflammatory, and severe inflammatory conditions in vitro. Alginate (Alg) and OCP-laden alginate (Alg/OCP) hydrogels were manufactured on the surface of 3D-printed Ti substrates and were characterized with wettability analysis, XRD, and FTIR. The electrochemical characterization of the samples was carried out with open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). It was observed that the hydrophilicity of Alg/OCP coatings was higher than that of pure Alg and that OCP phase crystallinity was increased when samples were subjected to simulated biological media. The corrosion resistance of uncoated and coated samples was lower in inflammatory and severe inflammatory environments vs. normal media, but the hydrogel coatings on 3D-printed Ti layers moved the corrosion potential towards more nobler values, reducing the corrosion current density in all simulated solutions. These measurements revealed that OCP particles in the Alg hydrogel matrix noticeably increased the electrical charge transfer resistance at the substrate and coating interface more than with Alg hydrogel alone.

Electro-Responsive Conductive Blended Hydrogel Patch

The proposed electro-responsive hydrogel has great benefit for transdermal drug delivery system (TDDS) applications. To improve the physical or chemical properties of hydrogels, a number of researchers have previously studied the mixing efficiencies of the blended hydrogels. However, few studies have focused on improving the electrical conductivity and drug delivery of the hydrogels. We developed a conductive blended hydrogel by mixing alginate with gelatin methacrylate (GelMA) and silver nanowire (AgNW). We demonstrated that and the tensile strength of blended hydrogels were increased by a factor of 1.8 by blending GelMA and the electrical conductivity was enhanced by a factor of 18 by the addition of AgNW. Furthermore, the GelMA-alginate-AgNW (Gel-Alg-AgNW) blended hydrogel patch enabled on-off controllable drug release, indicating 57% doxorubicin release in response to electrical stimulation (ES) application. Therefore, this electro-responsive blended hydrogel patch could be useful for smart drug delivery applications.

Optimized micro-sampling and computational analysis for SERS identification of red organic dyes on prints

The goals of this study were to develop a robust methodology and data analysis procedure to identify red dyes in artwork where dye collection is inaccessible by traditional methods. With Surface-Enhanced Raman Spectroscopy (SERS) it is possible to obtain identifying molecular information from dilute and degraded dyes. A minimally invasive, soft-mechanical sampling method to gently contact printed paper is described; using a customized polymeric hydrogel surface with an exposure area of about 1 mm², micrometer-diameter colorant particles were collected. To validate that the sample collection methodology is minimally invasive, test papers were photographed before and after sampling under UV and white light; and DART-MS analysis of the sampled area was conducted. A reference library of SERS spectra from binder (hide glue), dyes (safflower, sappan, and madder), and binder-dye mixtures was built and used by a spectral-matching genetic algorithm (GA). Fifty individual GA runs returned results that precisely matched at least one dye component in 48-50 of the 50 runs, and matched both dyes in a mixture between 29 and 50 of the 50 runs. Finally, in an artwork application, the methodologies were demonstrated on micro-samples from three areas of an 18th century Japanese woodblock print by Suzuki Harunobu in the collection of the Portland Art Museum, on which, madder dyes were positively identified. Conclusions and extensions from this work are expected to contribute to the body of knowledge about 18th c. Japanese woodblock prints.

Smart Electrochemical Portable Tools for Cultural Heritage Analysis: A Review

Protecting Cultural Heritage (CH) from corrosion and other environmental damages, mainly involving metallic or organic layers contained in artwork, represents a major challenge for conservation scientists. Electrochemical techniques provide useful information about the deterioration effects of metallic coatings and organic layers. Recently, Electrochemical Impedance Spectroscopy (EIS) has been successfully applied in the study of metallic corrosion. However, EIS has not succeeded in becoming a routine technique, due to problems regarding both instrumental apparatus (which is not ideal for in situ analysis, especially with previous cell configurations), and the difficulty with data processing. At the same time, new portable electrochemical sensors, immunosensors, and biosensors have successfully made a scientific impact, mainly with in situ diagnosis of organic components contained in CH objects. For this purpose, this review presents two sections: the first describes the analytical optimization of impedance electrochemical cell geometries that are suitable for in situ metal-coating investigation; the second reports on the assembly of small electrochemical sensors, immunosensors, and biosensors, which useful for in situ organic layer characterization. This overview summarizes the state of the art regarding the application of electrochemical techniques and small electrochemical devices as alternative tools for the understanding of CH.

Preparation and Property Evaluation of Conductive Hydrogel Using Poly (Vinyl Alcohol)/Polyethylene Glycol/Graphene Oxide for Human Electrocardiogram Acquisition

Conductive hydrogel combined with Ag/AgCl electrode is widely used in the acquisition of bio-signals. However, the high adhesiveness of current commercial hydrogel causes human skin allergies and pruritus easily after wearing hydrogel for electrodes for a long time. In this paper, a novel conductive hydrogel with good mechanical and conductive performance was prepared using polyvinyl alcohol (PVA), polyethylene glycol (PEG), and graphene oxide (GO) nanoparticles. A cyclic freezing⁻thawing method was employed under processing conditions of -40 °C (8 h) and 20 °C (4 h) separately for three cycles in sequence until a strong conductive hydrogel, namely, PVA/PEG/GO gel, was obtained. Characterization (Fourier transform infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy) results indicated that the assembled hydrogel was successfully prepared with a three-dimensional network structure and, thereafter, the high strength and elasticity due to the complete polymeric net formed by dense hydrogen bonds in the freezing process. The as-made PVA/PEG/GO hydrogel was then composited with nonwoven fabric for electrocardiogram (ECG) electrodes. The ECG acquisition data indicated that the prepared hydrogel has good electro-conductivity and can obtain stable ECG signals for humans in a static state and in motion (with a small amount of drift). A comparison of results indicated that the prepared PVA/PEG/GO gel obtained the same quality of ECG signals with commercial conductive gel with fewer cases of allergies and pruritus in volunteer after six hours of wear.