Developing natural polymers for skin wound healing

Natural polymers are complex organic molecules that occur in the natural environment and have not been subjected to artificial synthesis.They are frequently encountered in various creatures,including mammals,plants,and microbes.The aforementioned polymers are commonly derived from renewable sources,possess a notable level of compatibility with living organisms,and have a limited adverse effect on the environment.As a result,they hold considerable significance in the development of sustainable and environmentally friendly goods.In recent times,there has been notable advancement in the investigation of the potential uses of natural polymers in the field of biomedicine,specifically in relation to natural biomaterials that exhibit antibacterial and antioxidant characteristics.This review provides a comprehensive overview of prevalent natural polymers utilized in the biomedical domain throughout the preceding two decades.In this paper,we present a comprehensive examination of the components and typical methods for the preparation of biomaterials based on natural polymers.Furthermore,we summarize the application of natural polymer materials in each stage of skin wound repair.Finally,we present key findings and insights into the limitations of current natural polymers and elucidate the prospects for their future development in this field.

Synthetic polymers:A review of applications in drilling fluids

With the growth of deep drilling and the complexity of the well profile,the requirements for a more complete and efficient exploitation of productive formations increase,which increases the risk of various complications.Currently,reagents based on modified natural polymers(which are naturally occurring compounds)and synthetic polymers(SPs)which are polymeric compounds created industrially,are widely used to prevent emerging complications in the drilling process.However,compared to modified natural polymers,SPs form a family of high-molecular-weight compounds that are fully synthesized by undergoing chemical polymerization reactions.SPs provide substantial flexibility in their design.Moreover,their size and chemical composition can be adjusted to provide properties for nearly all the functional objectives of drilling fluids.They can be classified based on chemical ingredients,type of reaction,and their responses to heating.However,some of SPs,due to their structural characteristics,have a high cost,a poor temperature and salt resistance in drilling fluids,and degradation begins when the temperature reaches 130℃.These drawbacks prevent SP use in some medium and deep wells.Thus,this review addresses the historical development,the characteristics,manufacturing methods,classification,and the applications of SPs in drilling fluids.The contributions of SPs as additives to drilling fluids to enhance rheology,filtrate generation,carrying of cuttings,fluid lubricity,and clay/shale stability are explained in detail.The mechanisms,impacts,and advances achieved when SPs are added to drilling fluids are also described.The typical challenges encountered by SPs when deployed in drilling fluids and their advantages and drawbacks are also discussed.Economic issues also impact the applications of SPs in drilling fluids.Consequently,the cost of the most relevant SPs,and the monomers used in their synthesis,are assessed.Environmental impacts of SPs when deployed in drilling fluids,and their manufacturing processes are identified,together with advances in SP-treatment methods aimed at reducing those impacts.Recommendations for required future research addressing SP property and performance gaps are provided.

Research Progress on the Preparation of Inorganic/Natural Materials Composite Microspheres

Microspheres are a new type of drug carrier with great potential for development and application.Natural polymers have good biocompatibility,biodegradability,and are easily dispersed in living organisms,making them suitable for preparing microspheres.Inorganic materials(mainly inorganic minerals)have excellent mechanical properties and are inexpensive and easy to obtain.Through the coupling and hybridization of natural polymers and inorganic materials,they can complement each other's advantages and synergistically enhance efficiency,resulting in many excellent physical and chemical properties.Inorganic materials/natural polymer composite microspheres can be prepared by modifying natural polymers with inorganic materials through various methods such as emulsification crosslinking,solution mixing,in-situ synthesis,extrusion,etc.The application of inorganic materials/natural polymer composite microspheres in drug delivery systems has significant sustained-release effects,is safe and non-toxic,and the cost of carrier materials is relatively low,which has certain significance for the development of new drug carriers.This article reviews the recent research on the preparation,drug loading and release properties of inorganic material/natural polymer composite microspheres,analyzes the advantages and disadvantages of commonly used preparation methods,and looks forward to the development direction of composite microspheres.

Natural polymers based triboelectric nanogenerator for harvesting biomechanical energy and monitoring human motion

Triboelectric nanogenerator(TENG)has been proved as a promising energy harvester in recent years,but the challenges of exploring economically triboelectric materials still exist and have aroused interests of many researchers.In this paper,chitosan-silk fibroin-airlaid paper composite film(CSA film)was fabricated and then the CSA film based-triboelectric nanogenerator(CSA-TENG)was constructed,which presents an opportunity for natural polymers to be applied in triboelectric materials.Due to the excellent electron donating ability of CSA film,the CSA-TENG can harvest environmental energy with a high efficiency.More importantly,the as-designed CSA film based dual-electrode triboelectric nanogenerator(CSA-D-TENG)is successfully assembled into hand clapper and trampoline to harvest mechanical energies generated by human bodies,it is also capable of monitoring human movement while harvesting biomechanical energies.This work provides a simple and environmental-friendly way to develop TENG for biomechanical energies harvesting and human motion monitoring.

Application of Pomegranate Rind Extract for Improvement of Functional Properties of Various Materials—A Critical Review

Pomegranate rind is abundantly available as a waste material. Pomegranate Rind Extract (PRE) can be applied to cotton fabrics for its natural colours, as a mordanting agent and also for imparting certain functional properties such as fire retardancy and antimicrobial properties. This paper reviews the feasibility of Pomegranate Rind Extract to improve the functional properties of cellulosic fabrics. Studies show that varying concentrations and higher temperatures that were used to apply the extract on the fabric, resulted in enhanced functional properties. At a particular concentration, the treated fabric showed a 15 times lower burning rate in comparison with the control fabric. Also, antimicrobial efficacy has been observed against Gram-positive and Gram-negative bacteria. Due to the natural colouring material, it can be used as a natural dye on cotton material. The fire retardancy of pomegranate rind extract was tested on jute material under varying alkalinity. Research has indicated that pomegranate rind extract could be used to dye polyamide as well. The rubbing and wash fastness of the finished fabrics is good. The light fastness was fair, and its antibacterial efficiency against tested bacteria was good.

Material Selection of a Natural Fibre Reinforced Polymer Composites using an Analytical Approach

Material selection has become a critical part of design for engineers,due to availability of diverse choice of materials that have similar properties and meet the product design specification.Implementation of statistical analysis alone makes it difficult to identify the ideal composition of the final composite.An integrated approach between statistical model and micromechanical model is desired.In this paper,resultant natural fibre and polymer matrix from previous study is used to estimate the mechanical properties such as density,Young’s modulus and tensile strength.Four levels of fibre loading are used to compare the optimum natural fibre reinforced polymer composite(NFRPC).The result from this analytical approach revealed that kenaf/polystyrene(PS)with 40%fibre loading is the ideal composite in automotive component application.It was found that the ideal composite score is 1.156 g/cm^(3),24.2 GPa and 413.4 MPa for density,Young’s modulus and tensile strength,respectively.A suggestion to increase the properties on Young’s modulus are also presented.This work proves that the statistical model is well incorporated with the analytical approach to choose the correct composite to use in automotive application.

3D printedβ-sheet-reinforced natural polymer hydrogel bilayer tissue engineering scaffold

It remains a significant challenge to fabricate natural polymer(NP)hydrogels with anti-swelling ability and high strengths in the physiological environment.Herein,theβ-sheet-reinforced NP hydrogel is developed by copolymerizing methacrylated gelatin(GelMA)and methacrylated silk fibroin(SFMA)in aqueous solution,followed by ethanol treatment(named GelMA-SFMAAL).Theβ-sheets formed by SFMA can act as a stable physical crosslink to enhance the mechanical properties and prolong the degradation of the GelMA network.Importantly,the chemical crosslinking in the GelMA-SFMA hydrogel prevents excessive aggregation of hydrophobicβ-sheets,thereby avoiding the formation of brittle hydrogel.The obtained GelMA-SFMA-AL hydrogels exhibit considerably enhanced mechanical properties(Young's modulus:0.89–3.68 MPa;tensile strength:0.31–0.96 MPa;toughness:0.09–0.63 MJ/m^(3);compressive modulus:0.78–2.20 MPa;compressive strength:2.65–5.93 MPa)compared with GelMA-SFMA hydrogels(Young's modulus:0.04–0.13 MPa;tensile strength:0.04–0.07 MPa;toughness:0.01–0.02 MJ/m^(3);compressive modulus:0.03–0.09 MPa;compressive strength:0.30–0.64 MPa).A bilayer osteochondral scaffold is constructed via digital light processing(DLP)three-dimensiaonl(3D)printing technology,comprising GelMA-SFMA@diclofenac sodium(DS)-AL as the top layer and GelMA-SFMA@bioactive glass(BG)-AL as the bottom layer.The bilayer hydrogel scaffold is demonstrated to support cell attachment and spreading,and facilitate osteogenic differentiation of rat bone marrow stem cells in vitro.In vivo implantation experiment suggests this bilayer scaffold is promising to be used for osteochondral tissue regeneration.

Multifunctional binder designs for lithium-sulfur batteries

Lithium-sulfur(Li-S)batteries are promising next-generation high energy density batteries but their practical application is hindered by several key problems,such as the intermediate polysulfide shuttling and the electrode degradation caused by the sulfur volume changes.Binder acts as one of the most essential components to build the electrodes of Li-S batteries,playing vital roles in improving the performance and maintaining the integrity of the cathode structure during cycling,especially those with high sulfur loadings.To date,tremendous efforts have been devoted to improving the properties of binders,in terms of the viscosity,elasticity,stability,toughness and conductivity,by optimizing the composition and structure of polymer binders.Moreover,the binder modification endows them strong polysulfide trapping ability to suppress the shuttling and decreases the swelling to maintain the porous structure of cathode.In this review,we summarize the recent progress on the binders for Li-S batteries and discuss the various routes,including the binder combination use,functionalization,in-situ polymerization and ion cross-linking,etc.,to enhance their performance in stabilizing the cathode,building the high sulfur loading electrode and improving the cyclic stability.At last,the design principles and the problems in further applications are also highlighted.

Preliminary Study on Tensile and Impact Properties of Kenaf/Bamboo Fiber Reinforced Epoxy Composites

The application of natural fibers as reinforcement in composite material has increased due to environmental concerns,low cost,degradability and health concerns.The purpose of this study is to identify the best type of bamboo fibers to be used as reinforcement for kenaf(K)/bamboo hybrid composite.There were three types of bamboo fibers evaluated in this study which include bamboo mat(B),bamboo fabric(BF)and bamboo powder(BP).Chemical composition of B,BF,BP and K fibers were analyzed in this study.The effect of different types of bamboo fibers on tensile,impact,and morphological properties were investigated.The B/epoxy composites displayed the highest tensile strength(53.03 MPa)while K/epoxy composite had the highest tensile modulus(4.71 GPa).Scanning electron micrographs of B/epoxy composites displayed better fiber/matrix interfacial bonding in comparison to other studied composites.Results showed that impact strength of BF-based composite was highest(45.70 J/m).In conclusion,the tensile strength of B/epoxy composite is superior to the other bamboo reinforced composites and will be further evaluated in the next study.

Antioxidant activity of bovine serum albumin binding amino acid Schiff-bases metal complexes

Glutamic acid-salicylaldehyde Schiff-base metal complexes are bound into bovine serum albumin （BSA）, which afforded BSA binding Schiff-base metal complexes （BSA-SalGluM, M=Cu, Co, Ni, Zn）. The BSA binding metal complexes were characterized by UV-vis spectra and Native PAGE. It showed that the protein structures of BSA kept after coordinating amino acid Schiff-bases metal complexes. The effect of the antioxidant activity was investigated. The results indicate that the antioxidant capacity of BSA increased more than 10 times after binding Schiff-base metal complexes.

Preparation and Application of Chitosan-based Polyelectrolyte Complex Materials: An Overview

Chitosan,a renewable,non-toxic,and natural cationic polyelectrolyte,can be combined with many anionic polyelectrolytes(such as sodium alginate,hyaluronic acid,xylan,and gelatin)via electrostatic forces to form chitosan-based polyelectrolyte composites under certain conditions.This review summarizes various methods of preparing chitosan-based polyelectrolyte composites and analyzes their applications in clinical medicine and agriculture,as well as pharmaceutical,tissue,food,environmental,and textile engineering fields.The future development direction and potential of chitosan-based polyelectrolytes are also discussed.

Adsorptive Removal of Heavy Metals from Aqueous Solution with Environmental Friendly Material—Exhausted Tea Leaves

In this study adsorptive removal of Pb(II) and Cu(II) from aqueous solution by using environmental friendly natural polymers present in exhausted tea leaves has been studied. The biosorbent was modified with dimethylamine to introduce N-functional groups on the surface of adsorbent. The modified adsorbent was characterized by elemental analysis, zeta potential analysis, SEM, DRFTIR, XRD and TG/DTA analysis to conform the modification. Adsorption capacity of the adsorbent was determined as the function of pH of the solution, initial concentration of the solution and contact time. The adsorption experiments were performed using batch experiments. The maximum adsorption capacities of the adsorbent were found to be 91.68 and 71.20 mg/g for Pb(II) and Cu(II), respectively. To minimize the process cost, regeneration of the biosorbent and recovery of metal ions was explored by desorption study. The results indicate that the adsorbent holds great potential for the sequestration of Pb(II) and Cu(II) from their aqueous solution. Hence the modified exhausted tea leaves (MTL) have been investigated as a new cost effective and efficient biosorbent for removal of Pb(II) and Cu(II) from their aqueous solution.

Tea eggs-inspired high-strength natural polymer hydrogels

Natural polymer(NP)hydrogels are an irreplaceable class of biomaterials owing to their identified biosafety;however,the intrinsic poor mechanical strengths severely limit their applications as structural tissue engineering scaffolds.Inspired by the stiffening albumen gel of tea eggs,a traditional Chinese snack,high-strength NP hydrogels are constructed by simply soaking in aqueous solution of tea polyphenols(TP),an active ingredient extracted from tea.The TP-treated representative NP hydrogels exhibit considerably enhanced multifaceted mechanical properties with maximum 19-/30-,8.4-,6.1-,72-fold increases in tensile/compressive strengths,Young’s modulus,elongation at break and facture toughness,respectively,compared with pristine hydrogels,primarily due to the hydrogen bonding interactions between TP and NP chains.The TP-treated NP hydrogels can resist different large deformations,which cannot be achieved by their original species at all.In aqueous solution,the TP-treated NP hydrogels can still maintain robust mechanical performances,in spite of somewhat decline in strengths with release of TP,which just favorably affords increased water contents,antibacterial and antioxidant activities.GelMA-TP hydrogel is shown to facilitate wound healing in a full-thickness skin defect model.Importantly,the weak 3D printed GelMA scaffolds are significantly strengthened by TP treatment,broadening the possibility for customizing individualized bioscaffolds.

Hyaluronan is a natural and effective immunological adjuvant for protein-based vaccines

One of the main goals of vaccine research is the development of adjuvants that can enhance immune responses and are both safe and biocompatible.We explored the application of the natural polymer hyaluronan(HA)as a promising immunological adjuvant for protein-based vaccines.Chemical conjugation of HA to antigens strongly increased their immunogenicity,reduced booster requirements,and allowed antigen dose sparing.HA-based bioconjugates stimulated robust and long-lasting humoral responses without the addition of other immunostimulatory compounds and proved highly efficient when compared to other adjuvants.Due to its intrinsic biocompatibility,HA allowed the exploitation of different injection routes and did not induce inflammation at the inoculation site.This polymer promoted rapid translocation of the antigen to draining lymph nodes,thus facilitating encounters with antigen-presenting cells.Overall,HA can be regarded as an effective and biocompatible adjuvant to be exploited for the design of a wide variety of vaccines.

Tuning Zn^(2+) coordination tunnel by hierarchical gel electrolyte for dendrite-free zinc anode

Aqueous zinc-ion batteries(ZIBs)are perceived as one of the most upcoming grid-scale storage systems.However,the issues of electrode dissolution,dendrite formation,and corrosion in traditional liquid electrolytes have plagued its progress.In this work,Zn dendrite growth and side reactions are effectively suppressed by a highly-confined tannic acid(TA)modified sodium alginate(SA)composite gel electrolyte(TA-SA).The ion-confinement effect is enhanced by divalent zinc ions coordinated with carboxyl groups and chelated with phenolic hydroxyl groups,thus guiding and regulating Zn deposition to achieve steady zinc plating/stripping behavior.As a consequence,the Zn/TA-SA/NH_(4)V_(4)O_(10) full cells deliver a high specific capacity of 238.6 mAh g^(-1) and maintain 94.51%over 900 cycles at 2 A g^(-1).Notably,after resting over 5 d,the capacity can be stabilized with a capacity retention of 97.25%after 200 cycles at 2 A g^(-1).This highlyconfined and hydrogen bond-strengthened gel electrolyte may provide an effective strategy for the future development of quasi-solid-state metal batteries.

Wearable and humidity-resistant biomaterials-based triboelectric nanogenerator for high entropy energy harvesting and self-powered sensing

Triboelectric nanogenerator(TENG)provides a new solution to the energy supply by harvesting high entropy energy.However,wearable electronic devices have high requirements for flexible,humidity-resistant,and low-cost TENG.Here,environmentfriendly and multi-functional wheat starch TENG(S-TENG)was made by a simple and green method.The open-circuit voltage and short-circuit current of S-TENG are 151.4 V and 47.1μA,respectively.S-TENG can be used not only to drive and intelligently control electronic equipment,but also to effectively harvest energy from body movements and wind.In addition,the output of S-TENG was not negatively affected with the increase in environmental humidity,but increased abnormally.In the range of 20%RH–80%RH,S-TENG can be potentially used as a sensitive self-powered humidity sensor.The S-TENG paves the way for large-scale preparation of multi-functional biomaterials-based TENG,and practical application of self-powered sensing and wearable devices.

Approaches in extracellular matrix engineering for determination of adhesion molecule mediated single cell function

The native extracellular matrix （ECM） and the cells that comprise human tissues are together engaged in a complex relationship; cells alter the composition and structure of the ECM to regulate the material and biologic properties of the surrounding environment while the composition and structure of the ECM modulates cellular processes that maintain healthy tissue and repair diseased tissue. This reciprocal relationship occurs via cell adhesion molecules （CAMs） such as integrins, selectins, cadherins and IgSF adhesion molecules. To study these celI-ECM interactions, researchers use two-dimensional substrates or three-dimensional matrices composed of native proteins or bioactive peptide sequences to study single cell function. While two-dimensional snbstrates provide valuable information about cell-ECM interactions, three-dimensional matrices more closely mimic the native ECM; cells cultured in three-dimensional matrices have demonstrated greater cell movement and increased integrin expression when compared to cells cultured on two-dimensional substrates. In this article we review a number of cellular processes （adhesion, motility, phagocytosis, differentiation and survival） and examine the cell adhesion molecules and ECM proteins （or bioactive peptide sequences） that mediate cell functionality.

Luminescent polymer electrolytes based on chitosan and containing europium triflate

Solid polymer electrolytes based on chitosan and europium triflate were prepared by solvent casting and characterized by X-ray diffraction, scanning electron microscopy （SEM）, atomic force microscopy （AFM）, and photoluminescence spectroscopy. The X-ray diffraction exhibited that the samples were essentially amorphous with organized regions over the whole range of the salt content studied. The AFM analysis demonstrated that the smoother sample had roughness of 4.39 nm. Surface visualization through SEM revealed good homogeneity without any phase separation for more conductive samples and the less conductive showed some im- perfections on the surface. The emission and excitation spectra displayed the characteristic bands of Eu（CF3SO3）3 in addition to broad bands corresponding to the polymer host. The excited state 5D0 lifetime values ranged from 0.29-0.37 ms for the studied samples.

Keratin-Based materials for biomedical applications

Keratin constitutes the major component of the feather,hair,hooves,horns,and wool represents a group of biological material having high cysteine content(7–13%)as compared to other structural proteins.Keratin-based biomaterials have been investigated extensively over the past few decades due to their intrinsic biological properties and excellent biocompatibility.Unlike other natural polymers such as starch,collagen,chitosan,the complex three-dimensional structure of keratin requires the use of harsh chemical conditions for their dissolution and extraction.The most commonly used methods for keratin extraction are oxidation,reduction,steam explosion,microbial method,microwave irradiation and use of ionic liquids.Keratin-based materials have been used extensively for various biomedical applications such as drug delivery,wound healing,tissue engineering.This review covers the structure,properties,history of keratin research,methods of extraction and some recent advancements related to the use of keratin derived biomaterials in the form of a 3-D scaffold,films,fibers,and hydrogels.

Wet-spinning of Regenerated Silk Fiber from Aqueous Silk Fibroin Solutions: Influence of Calcium Ion Addition in Spinning Dope on the Performance of Regenerated Silk Fiber

Ca（II） ions are added in the spinning dope to adjust the solidification rate of regenerated silk fibroin （RSF） solution during the wet-spinning process since Ca（II） ions are proved to be favorable to maintain the stable silk fibroin network in our previous work. The results show that when Ca（II）/RSF ratios are 1/50 and 1/20, the resulted RSF fibers exhibit good performance with the breaking energy more than 70 kJ/kg. However, higher Ca（II）/RSF ratio （for example, 1/10） hinders the solidification of spinning dope and results in poor RSF fibers. These observations together with earlier papers from this laboratory confirm that to produce tough silk fibers the spinning conditions must allow sufficient time for the adjustment of silk fibroin molecular chains.