Abstract Nowadays, collagen hydrogels with both good physicochemical and antibacterial properties for tissue engineering have drawn broad attention. Herein, a biocompatible and antibacterial collagen hydrogel is developed via alginate dialdehyde (ADA) modification and tetracycline hydrochloride (TC) loading based on Schiff's base formation. Fourier transform infrared spectroscopy and X‐ray diffraction spectra suggest the maintenance of collagen structure integrity after ADA modification. The modification significantly contributes to the improved swelling property, resistance against type I collagenase, and strengthens storage modulus of hydrogels with an increase of ADA concentrations. Meanwhile, dynamic release curves of tetracycline hydrochloride (TC)‐loaded hydrogels describe the burst release at the first 15 min then a gradual release, hydrogels act ideally as carriers in antibacterial activity. Furthermore, in vitro biocompatibility and antibacterial properties are successfully confirmed from the fabricated collagen hydrogels. This physicochemical‐ and antibacterial‐property–improved collagen hydrogel would be a potential candidate for wound healing as a scaffold.
Surface Enhanced Raman Spectroscopy (SERS) is always challenging for the detection of complex samples due to the pre-processing issues. Therefore, there is a need to develop a high-performance SERS platform that can avoid pre-processing problems and simultaneously enrich target molecules. In this work, we encapsulated cationic cellulose nanofibers(CCNF) stabilized Ag NCs in polyacrylamide hydrogels via photo-crosslinking to construct a high-performance SERS platform for rapid separation, concentration and enrichment without pretreatment. Ag NCs/CCNF/PAAM hydrogels have good swelling and shrinking properties, which are favorable for enriching the substances to be measured and improving the sensitivity of the SERS platform. The limit of detection (LOD) was as low as 9.33×10−11 M for the detection of the dye molecule R6G. Hydrogel has a barrier effect on macromolecules and hydrophobic substances in complex samples, and hydrophilic small molecules can enter the SERS platform quickly, and the SERS platform has good selectivity. Therefore, we performed the SERS assay for hydrophilic anticancer drugs in the plasma environment, where the hydrogel allowed doxorubicin hydrochloride (DOX) and 6-thioguanine (6-TG) to enter into the interior of the hydrogel, while hydrophobic substances such as plasma proteins and lipids in plasma were excluded from the hydrogel. As a validation, we performed spiking experiments on plasma from five lung cancer patients, and the assay was sensitive and reliable, with recoveries ranging from 89.02% to 110.99%.Based on the above results, Ag NCs/CCNF/PAAM hydrogels are promising for the real-time detection of drugs in clinical blood.
The key to SERS research is the substrate material with Raman signal enhancement effect. Compared with traditional nano metal particle SERS substrate materials, membrane materials have better uniformity, stability, and a wider range of applications. Membrane materials have already occupied an important position in two-dimensional SERS substrates. However, most of the SERS substrates based on membrane materials proposed in existing studies are difficult to adapt to most extreme environments, such as high or low pH, high salinity, corrosive solutions, etc. Moreover, the characteristics of "disposable product" also mean that more manpower and material resources are required in the preparation of SERS base materials. In this work, a composite membrane based on epoxy resin, cellulose paper and nanometal particles was proposed for the first time as a SERS substrate material. Based on the excellent stability of epoxy resin, the substrate material can still be used normally in environments such as -80℃-100℃, pH=1-13, strong acid solution with a concentration of ≤ 3%, and strong alkali solution with a concentration of ≤ 0.1M. At the same time, the cleanable properties endowed by the smooth surface make the material substrate recyclable and reusable. After 6 repeated uses, it still has a stable Raman signal enhancement effect.
Various parameters (time, initial concentration, pH value and temperature) are investigated. The results show that with increasing the temperature decreased the absorbance. The optimal condition is that the maximum adsorption is 0.47mg•g-1 at303K, pH 1. Adsorption process fits the Langmuir isotherm equation, the adsorption reaction is exothermal reaction.
Surface-enhanced Raman spectroscopy (SERS), as an emerging molecular-level detection technology, has attracted considerable research attention, especially in the context of substrate materials exhibiting Raman enhancement effects. Membrane materials, owing to their commendable uniformity, stability, and ease of modification, hold a pivotal position in the landscape of SERS substrate materials. However, existing SERS substrates based on membrane materials have limited adaptability to a spectrum of extreme environments, including but not limited to high or low pH, elevated salinity, and corrosive solutions. Additionally, SERS substrate materials are synonymous with "waste" and "high investment" because of their inherent disposable nature. This study introduces a pioneering approach, presenting a polymer composite membrane founded on epoxy resin, cellulose paper, and nanometal particles as a novel SERS substrate material. Given the outstanding stability of epoxy resin, the substrate material exhibits normal functionality in environments ranging from -80℃ to 100℃, with pH levels spanning 1 to 13, and in highly acidic solutions (concentration ≤ 3%) and highly alkaline solutions (concentration ≤ 0.1 M). Moreover, the cleanability inherent in the polymer composite membrane renders the substrate material recyclable. Experimental findings reveal that even after six repeated uses, the substrate material sustains a stable Raman signal enhancement effect. The integration of recyclability and heightened stability makes this SERS substrate material a promising candidate for real-time monitoring and batch testing in chemical production processes or other complex environments.
In the current era, the treatment of collagen hydrogels with natural phenolics for the improvement in physicochemical properties has been the subject of considerable attention. The present research aimed to fabricate collagen hydrogels cross-linked with gallic acid (GA) and ellagic acid (EA) at different concentrations depending on the collagen dry weight. The structural, enzymatic, thermal, morphological, and physical properties of the native collagen hydrogels were compared with those of the GA/EA cross-linked hydrogels. XRD and FTIR spectroscopic analyses confirmed the structural stability and reliability of the collagen after treatment with either GA or EA. The cross-linking also significantly contributed to the improvement in the storage modulus, of 435 Pa for 100% GA cross-linked hydrogels. The thermal stability was improved, as the highest residual weight of 43.8% was obtained for the hydrogels cross-linked with 50% GA in comparison with all the other hydrogels. The hydrogels immersed in 30%, 50%, and 100% concentrations of GA also showed improved swelling behavior and porosity, and the highest resistance to type 1 collagenase (76.56%), was obtained for 50% GA cross-linked collagen hydrogels. Moreover, GA 100% and EA 100% obtained the highest denaturation temperatures (Td) of 74.96 °C and 75.78 °C, respectively. In addition, SEM analysis was also carried out to check the surface morphology of the pristine collagen hydrogels and the cross-linked collagen hydrogels. The result showed that the hydrogels cross-linked with GA/EA were denser and more compact. However, the improved physicochemical properties were probably due to the formation of hydrogen bonds between the phenolic hydroxyl groups of GA and EA and the nitrogen atoms of the collagen backbone. The presence of inter- and intramolecular cross-links between collagen and GA or EA components and an increased density of intermolecular bonds suggest potential hydrogen bonding or hydrophobic interactions. Overall, the present study paves the way for further investigations in the field by providing valuable insights into the GA/EA interaction with collagen molecules.
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