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Abstract "Green" electronics represents an emerging area of research aimed at identifying natural materials that are applicable for environmentally safe and biodegradable devices. Iron (Fe) ions are used in gelatin matrixes (gelatin composites) prepared on commercially available flexible paper substrates through the solution method, thus, the "green" electronics were achieved. Although atomic force microscopy images show that fiber-based paper substrates result in rough Al/paper structure surfaces, the uniform interface between top Al electrodes and gelatin composites can be clearly observed in transmission electron microscopy images. This might be due to the gelatin composite acts as not only the resistive layer, but also the smoothing layer. Moreover, Fe ions play an important role in assisting redox reaction or filament formation. An Al/gelatin/Al/paper device has no resistive switching behavior. Meanwhile, devices with Fe ions on a paper substrate show reproducible resistive switching for 18 cycles, an ON/OFF ratio of over 105, and an excellent current distribution (coefficient of variation<60%). The ON/OFF ratio of the device after bending 180 cycles can be maintained at 104. The biodegradable gelatin materials have good ductility and potential in recyclable and green electronic applications. Graphical abstract Image Highlights • A green electronic with an Al/gelatin composite/Al/paper structure has been demonstrated. • The devices showed forming-free, an ON/OFF ratio of over 105, and uniform current distribution. The ON/OFF ratio of the device after bending 150 cycles can be maintained at 104. • A supply of Fe3+/Fe2+ ions from the gelatin composite can contribute to the resistance switching properties. [ABSTRACT FROM AUTHOR]

A severe decay process, catalyzed by acidity and metal ions, affects cellulose in historical manuscripts and books that contain iron gall inks. The inhibition of this process can be achieved by alkaline-earth nanoparticles dispersions in alcohols, which create a neutral environment in which both oxidation and depolymerization of cellulose are hindered. As a result of the degradation process, paper in historical manuscripts and books is fragile and very difficult to handle. A reinforcement intervention with gelatin and Japanese tissue could be used for the strengthening of historical manuscripts, even if this method could not prevent paper degradation due to iron gall inks. Therefore, a new method, combining a deacidification treatment based on calcium hydroxide nanoparticles and a reinforcement process using Japanese tissue has been developed and tested on mockups containing iron gall inks. The protective action arising from the combined treatment was evaluated by performing cellulose viscosimetric degree of polymerization (DPv) and pH measurements on artificially aged systems. Scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM-EDX) was used for the evaluation of calcium distribution from the deacidification agent within samples cross section. Determinations of DPv clearly showed that the degradation of untreated inked paper was significantly slowed down by the combined treatment. The method was also tested on original manuscripts from 16th and 18th century. SEM-EDX maps showed that the applied treatment, which raised the pH to an appropriate value, is homogenously distributed over the treated surfaces. [ABSTRACT FROM AUTHOR]

The detection of trypsin and its inhibitor is significantly important for both clinical diagnosis and disease treatment. Herein, we demonstrate a hydrogel-assisted paper-based lateral flow sensor for the detection of trypsin and its inhibitor for the first time. The gelatin hydrogel is hydrolyzed based on the gel-to-sol transition in the presence of trypsin, which results in the release of the trapped water molecules in the gelatin hydrogel. By placing one end of a pH indicator strip onto the hydrolyzed gelatin hydrogel, water is flowing along the pH indicator strip. However, in the absence of trypsin, water cannot flow along the pH indicator strip as the water molecules are trapped in the gelatin hydrogel. The detection limit of the system reaches as low as 1.0 × 10−6 mg/mL, and it is also applied to the quantitative detection of trypsin in human serum. In addition, the detection of a clinical drug aprotinin that is an inhibitor of trypsin is also successfully achieved. Noteworthy, only the gelatin hydrogel, pH indicator strip, and PS substrate are needed to fulfill the detection of trypsin without the need of other chemicals or reagents. Overall, we develop a particularly simple, elegant, robust, competitive, high-throughput, and low-cost approach for the rapid and label-free detection of trypsin and its inhibitor, which is very promising in the development of commercial products for sensing, diagnostic, and pharmaceutical applications. Besides, the hydrogel-assisted paper-based lateral flow sensor can also be employed to detect other analytes of interest by use of different stimuli-responsive hydrogel systems. • A hydrogel-assisted paper-based lateral flow sensor is developed for the detection of trypsin and its inhibitor. • The hydrolysis of the gelatin hydrogel by trypsin triggers release of the water trapped in the hydrogel. • The released water flows along a pH indicator strip, and the coverage ratio of the water mark is used to quantify trypsin. • This simple, convenient, and cost-effective method has high portability, remarkable sensitivity, and fast response time. • It shows excellent performance in label-free and high-throughput detection of trypsin in human serum. [ABSTRACT FROM AUTHOR]

We studied the aging behaviour of gelatin used to size paper. Thus far, research on the aging of paper has largely ignored the sizing agent. Degradation of the protein was characterised and the impact of paper components, such as cellulose, and aluminium potassium sulphate was evaluated. Whatman No. 1 filter papers sized with two types of gelatins (A and B) were prepared as model samples. Commercially sized modern papers (Arches) were also studied in order to compare laboratory samples with real artist papers. Both types of papers were artificially aged (80 °C, 50% relative humidity for 35 and 94 days). Historic papers were included in the study in order to compare artificially aged with naturally aged gelatin. The aqueous extracts from the papers were characterised by aqueous size-exclusion chromatography (SEC) using four PL-Aquagel-OH columns and UV photodiode array detection at 220, 254 and 280 nm. Results showed that gelatin undergoes hydrolysis upon aging, type A gelatin showing a faster degradation rate than type B. The result was an increase in the lower-molar-mass fractions, under 50 000 g mol−1, and especially in a characteristic fraction with a peak molecular mass (Mp) of 14 000 g mol−1. A significant decrease in the extraction yields of α-, β- and γ-chains occurred after aging. This was attributed to crosslinking, leading to the formation of less-soluble polypeptides with very high molar mass (>800 000 g mol−1). Less than 10% alum had no impact on the degradation rate; higher alum contents accelerated hydrolysis reactions. [Copyright &y& Elsevier]