The shortage of medical resources promotes medical treatment reform, and smart healthcare is a promising strategy to solve this problem. With the development of Internet, real-time health status is expected to be monitored at home by using flexible healthcare systems, which puts forward new demands on flexible substrates for sensors. Currently, the flexible substrates are mainly traditional petroleum-based polymers, which are not renewable. As a natural polymer, cellulose, owing to its wide range of sources, convenient processing, biodegradability and so on, is an ideal alternative. In this review, the application progress of nanocellulose in flexible sensors is summarized. The structure and the modification methods of cellulose and nanocellulose are introduced at first, and then the application of nanocellulose flexible sensors in real-time medical monitoring is summarized. Finally, the advantages and future challenges of nanocellulose in the field of flexible sensors are discussed.
Cellulose/chemistry* ; Hydrogels/chemistry* ; Polymers

OBJECTIVES: To establish an experimental method for evaluating material permeability of type I collagen hydrogels. METHODS: Using BSA-FITC as an indicator, by combining BSA-FITC with PBS they were used as permeability media, and using transwell load hydrogen sample to detect BSA-FITC transparent rate. RESULTS: In the concentration range of 100 μg·mL~0.781 μg·mL, the standard curve ≥ 0.99, Lower Limit of Quantity (LLOQ) is 3.125 μg·mL, RSD <5%, detection recovery rate is in the range of 80%~120%. CONCLUSIONS In this study, we established an experimental method for evaluating material permeability of hydrogel. The BSA-FITC transparent rate of type I collagen hydrogel was 100% at 28 h.
Collagen Type I ; chemistry ; Hydrogels ; chemistry ; Materials Testing ; Permeability

Wound repair is a common clinical problem, which seriously affects the quality of life of patients and also brings a heavy burden to the society. Hydrogel-based multifunctional dressing has shown strong potential in the treatment of acute and chronic wounds. In addition to its good histocompatibility, cell adhesion, and biodegradability, methacrylic anhydride gelatin (GelMA) hydrogel has also attracted much attention due to its low cost, mild reaction conditions, adjustable physicochemical properties, and wide clinical applications. In this paper, the characteristics of GelMA hydrogel and its research progress in wound repair are introduced, and the future development of multifunctional GelMA hydrogel dressing for wound treatment is prospected.
Humans ; Gelatin/chemistry* ; Hydrogels ; Anhydrides ; Quality of Life ; Methacrylates/chemistry*

OBJECTIVES: To design and prepare silk fibroin/hyaluronic acid composite hydrogel. METHODS: The thiol modified silk fibroin and the double-bond modified hyaluronic acid were rapidly cured into gels through thiol-ene click polymerization under ultraviolet light condition. The grafting rate of modified silk fibroin and hyaluronic acid was characterized by ¹H NMR spectroscopy; the gel point and the internal microstructure of hydrogels were characterized by rheological test and scanning electron microscopy; the mechanical properties were characterized by compression test; the swelling rate and degradation rate were determined by mass method. The hydrogel was co-cultured with the cells, the cytotoxicity was measured by the lactate dehydrogenase method, the cell adhesion was measured by the float count method, and the cell growth and differentiation on the surface of the gel were observed by scanning electron microscope and fluorescence microscope. RESULTS: The functional group substitution degrees of modified silk fibroin and hyaluronic acid were 17.99% and 48.03%, respectively. The prepared silk fibroin/hyaluronic acid composite hydrogel had a gel point of 40-60 s and had a porous structure inside the gel. The compressive strength was as high as 450 kPa and it would not break after ten cycles. The water absorption capacity of the composite hydrogel was 4-10 times of its own weight. Degradation experiments showed that the hydrogel was biodegradable, and the degradation rate reached 28%-42% after 35 d. The cell biology experiments showed that the cytotoxicity of the composite gel was low, the cell adhesion was good, and the growth and differentiation of the cells on the surface of the gel were good. CONCLUSIONS The photocurable silk fibroin/hyaluronic acid composite hydrogel can form a gel quickly, and has excellent mechanical properties, adjustable swelling rate and degradation degree, good biocompatibility, so it has promising application prospects in biomedicine.
Fibroins/chemistry* ; Hydrogels/chemistry* ; Hyaluronic Acid/chemistry* ; Biocompatible Materials/chemistry* ; Click Chemistry ; Sulfhydryl Compounds ; Silk/chemistry*

Cutaneous wounds are one of the commonest clinical diseases. At present, there are still many challenges in how to repair wounds quickly with high quality. With the rapid development and cross-integration of materials science and biomedicine, hydrogels that can integrate various excellent properties through flexible structural modification and combination of different functional components are widely applied in wound management and research. This paper attempted to summarize the role of hydrogel in promoting wound repair from the respects of matrix materials, special structures, and diverse functions of hydrogel.
Humans ; Hydrogels/chemistry* ; Wound Healing ; Soft Tissue Injuries

Droplet microfluidics technology offers refined control over the flows of multiple fluids in micro/nano-scale, enabling fabrication of micro/nano-droplets with precisely adjustable structures and compositions in a high-throughput manner. With the combination of proper hydrogel materials and preparation methods, single or multiple cells can be efficiently encapsulated into hydrogels to produce cell-loaded hydrogel microspheres. The cell-loaded hydrogel microspheres can provide a three-dimensional, relatively independent and controllable microenvironment for cell proliferation and differentiation, which is of great value for three-dimensional cell culture, tissue engineering and regenerative medicine, stem cell research, single cell study and many other biological science fields. In this review, the preparation methods of cell-loaded hydrogel microspheres based on droplet microfluidics and its applications in biomedical field are summarized and future prospects are proposed.
Hydrogels/chemistry* ; Microfluidics/methods* ; Microspheres ; Regenerative Medicine ; Tissue Engineering/methods*

Pulpitis, periodontitis, jaw bone defect, and temporomandibular joint damage are common oral and maxillofacial diseases in clinic, but traditional treatments are unable to restore the structure and function of the injured tissues. Due to their good biocompatibility, biodegradability, antioxidant effect, anti-inflammatory activity, and broad-spectrum antimicrobial property, chitosan-based hydrogels have shown broad applicable prospects in the field of oral tissue engineering. Quaternization, carboxymethylation, and sulfonation are common chemical modification strategies to improve the physicochemical properties and biological functions of chitosan-based hydrogels, while the construction of hydrogel composite systems via carrying porous microspheres or nanoparticles can achieve local sequential delivery of diverse drugs or bioactive factors, laying a solid foundation for the well-organized regeneration of defective tissues. Chemical cross-linking is commonly employed to fabricate irreversible permanent chitosan gels, and physical cross-linking enables the formation of reversible gel networks. Representing suitable scaffold biomaterials, several chitosan-based hydrogels transplanted with stem cells, growth factors or exosomes have been used in an attempt to regenerate oral soft and hard tissues. Currently, remarkable advances have been made in promoting the regeneration of pulp-dentin complex, cementum-periodontium-alveolar bone complex, jaw bone, and cartilage. However, the clinical translation of chitosan-based hydrogels still encounters multiple challenges. In future, more in vivo clinical exploration under the conditions of oral complex microenvironments should be performed, and the combined application of chitosan-based hydrogels and a variety of bioactive factors, biomaterials, and state-of-the-art biotechnologies can be pursued in order to realize multifaceted complete regeneration of oral tissue.
Chitosan/chemistry* ; Tissue Engineering ; Hydrogels/chemistry* ; Biocompatible Materials/chemistry* ; Cartilage ; Tissue Scaffolds/chemistry*

Functional designing of natural amino acids (NAA) has received considerable attention in recent years due to its excellent biocompatibility. A novel self-assembling NAA, peptide RAG-16, was designed by hybridizing the characteristic silk fibroin motif (Gly-Ala) with an ionic complementary peptide sequence (Arg-Ala-Asp-Ala) in our study. The self-assembly structure, viscoelastic property, and cyto compatibility of the peptide were investigated by atomic force microscopy, rheometer, Fourier transform infrared spectrum, and inverted fluorescence microscope. RAG-16 was able to form a three-dimensional compact network structure in water. High mechanical performance of the peptide hydrogel was found due to the increase of the silk I structure from inserted fibroin motif segment. Fluorescence staining showed that vast majority of MC3T3-E1 cells in the RAG-16 hydrogel could adhere to, survive, and distribute on different planes. To sum up, in this experiment, the functional designing of the NAA has exhibited its potential application in biomedical field.
Amino Acids ; chemistry ; Biocompatible Materials ; chemistry ; Fibroins ; chemistry ; Hydrogels ; chemistry ; Models, Molecular ; Nanostructures ; chemistry ; ultrastructure ; Peptides ; chemistry ; Silk ; chemistry

In this study, we prepared various matrices of hydrogel patches and studied their cross-linking mechanism by observing their rheological properties, which could provide theoretical basis and deep technical support for further industrial development of hydrogel patch. Rheology method was used to do the amplitude scanning and single-frequency scanning for various hydrogel matrix, under the condition of oscillation mode of the rheometer. Then the linear viscoelastic region, composite modulus value, as well as changes in slope with time of the composite modulus and phase angle of various hydrogel matrix were analyzed in detail. The results showed that the stability of matrix was mainly determined by hydrogel frame; only in acidic environment, the cross-linking reaction between cross-linker and hydrogel frame can occur; elasticity of matrix can be decreased by organic acid and the effect level was related to the ratio of the number of carboxyl and hydroxyl (-COO(-)/-OH) in adjusters: if the ratio was not equal, the higher -COO(-)/-OH in adjusters would be the less elasticity of matrix decreased; the cross-linking speed of matrix was determined by adjuster, the cross-linking speed of matrix contain different adjusters was ranged in following order: matrix containing tartaric acid > matrix containing lactic acid > matrix containing malic acid > matrix containing citric acid; the cross-linking speed of matrix was not uniform in the whole cross-linking process.
Citric Acid ; chemistry ; Cross-Linking Reagents ; chemistry ; Hydrogels ; chemistry ; Lactic Acid ; chemistry ; Malates ; chemistry ; Rheology ; Tartrates ; chemistry ; Viscosity

Gelatin and hydroxyapatite were introduced to polyvinyl alcohol (PVA) hydrogel with an attempt to enhance the performances of PVA hydrogel. Through a reiterative freezing-thawing methods, three kinds of PVA composite hydrogels were prepared. The mechanical performances of these composite hydrogels with the same PVA and HA content but varying gelatin content, such as tensile strength, elasticity modulus, creep curve, relaxation curve and friction coefficient were evaluated by using a computer-controlled universal electronic mechanical testing machine and a UMT-II frictional testing machine. The additional effects of hydroxylapatite and varying gelatin on the performances of composite PVA hydro-gels were analyzed. It was found that the gelatin content directly influenced the physical performances of PVA composite hydrogels; but no linear relationship was recorded. PVA composite hydrogel containing 2wt-% gelatin gave optimal results, i.e. tensile strength of 5.5MPa, compressive elastical modulus of 1.48MPa, creeping rate of 31% in 45 minutes, stress relaxing rate of 40.3%, and the starting friction coefficient of 0.332.
Elastic Modulus ; Friction ; Hydrogels ; chemical synthesis ; chemistry ; Mechanical Phenomena ; Polyvinyl Alcohol ; chemical synthesis ; chemistry ; Tensile Strength