Composite Microspheres Research Articles

Preparation of TiO2 nanoparticles decorated porous carbon via a pseudo co-templating strategy and their application as substrates for high performance cathode of Li[sbnd]S batteries

Lithium‑sulfur batteries (LSBs) with a high theoretical specific capacity are considered as one of the most promising energy storage devices for next-generation. However, issues such as the insulation of pristine sulfur, the shuttle effect of polysulfides (LiPSs), and the volume change of sulfur cathode during cycling hinder their commercial applications. In this work, composite microspheres of TiO2@p-C consisting of porous carbon decorated with TiO2 nanoparticles, have been designed and synthesized aiming to confine and trap the polysulfides inside the porous substrates and to improve the kinetics of the electrochemical reaction therein. TiO2 particles with size of a few nanometers are prepared by a tetraethyl ammonium hydroxide assisted sol-gel method. Composite microspheres of TiO2@p-C are created through spray drying technique using chitosan as carbon source, and nanoparticles of SiO2 with TiO2 as co-template while selectively etching of the former. The confinement effects via the pores in the TiO2@p-C microspheres and the affinity between the polar TiO2 moieties and the polysulfide species work synergistically, alleviating the effusion of the polysulfides and promoting the conversion reaction of them as well. As a result, the shuttle effect of polysulfides can be inhibited obviously. Significantly, the S@TiO2@p-C-2 composite cathode exhibits excellent cyclic performance of 1263 mAh g−1 at 0.2C and maintains still a discharge capacity of 809 mAh g−1 after 100 charge and discharge cycles. At a current density of 2C, it still delivers an outstanding specific capacity of 772 mAh g−1. In the case of high sulfur load up to 90 wt%, the discharge capacity of S@TiO2@p-C-2 composite electrode could still maintain at 469.5 mAh g−1 after 100 cycles under current density of 0.2C.

The bimetallic 3,5-dinitrobenzoate composites: A flexible-synergistic catalysts for high-performance decomposition of ammonium perchlorate

Composites of metal complexes have catalytic effects on the thermal decomposition of ammonium perchlorate (AP), while the kinetics and mechanism studies of the processes are seldom mentioned. Here, composite microspheres of cupric 3,5-dinitrobenzoate and cobalt 3,5-dinitrobenzoate [(3,5-DNB)Cox•Cuy] were synthesized and employed to research the kinetics and mechanism of AP catalytic decomposition. The decomposition peak temperature of AP in the presence of the (3,5-DNB)Cox•Cuy microspheres decreased from 403 °C (pure AP) to 288 °C, and the released heat increased by 384.5–745.6 J/g. Notably, the (3,5-DNB)Cox•Cuy microspheres significantly improved the kinetic rate constant by 1.83–37.75 times. The (3,5-DNB)Cox•Cuy microspheres exhibited higher activity than their corresponding single components for the thermal decomposition of AP, indicating excellent synergistic effects and proposing a possible mechanism. Understanding the kinetics and mechanism of the catalytic process developed in this study could further improve the decomposition performance of AP.

Preparation of Super Slippery Surface of Polyimide Composite Microspheres

Preparation of Super Slippery Surface of Polyimide Composite Microspheres

Water-in-water emulsions stabilized by nano-chitin

A water-in-water (W/W) emulsion consists of microdroplets was formed by the spontaneous liquid–liquid separation by mixing polyacrylic acid and chitosan oligosaccharide in water, and these microdropletes were stabilized by nano-chitin, formed water-in-water Pickering emulsions. By taking the advantage of interfacial adsorption of nano-chitin, the W/W emulsion droplets composed of polyacrylic acid/chitosan oligosaccharide (COS/PAA) polyelectrolyte coacervate were successfully stabilized. Research results indicated that composite microspheres were formed by the nano-chitin stabilized COS/PAA emulsion, and the size of these composite microspheres was related to the concentration and morphology of the nano-chitin. As the concentration of nano-chitin increases, the size of the composite microspheres first increases and then decreases, gradually becoming more uniform; whereas a decrease in the length of nano-chitin will lead to an increase in the size of the composite microspheres. The formation of composite microspheres may be due to the electrostatic interactions between nano-chitin and the emulsion droplets. In addition, the composite microspheres exhibit the best release effect for berberine hydrochloride at a pH value of 3.

Thermo-responsible PNIPAM-grafted polystyrene microspheres for mesenchymal stem cells culture and detachment.

The preparation of cells is a critical step in cell therapy. To ensure the effectiveness of cells used for clinical treatments, it is essential to harvest adherent cells from the culture media in a way that preserves their high viability and full functionality. In this study, we developed temperature-responsive poly(N-isopropylacrylamide) (PNIPAM)-grafted polystyrene (PS) microspheres using reversible addition-fragmentation chain transfer polymerization. These microspheres allow for the non-destructive harvesting of cultured cells through temperature changes. The composition and physicochemical properties of the PNIPAM-grafted PS microspheres were confirmed using infrared spectroscopy, elemental analysis, dynamic light scattering, and thermogravimetric analysis.In vitroexperiments demonstrated that these microspheres exhibit excellent biocompatibility, supporting the adhesion and proliferation of various cells. Moreover, the microspheres showed good temperature responsiveness in thermosensitive detachment experiments with GFP-HepG2cells and umbilical cord mesenchymal stem cells (UC-MSCs). Additionally, through orthogonal experiments, we identified a cell detachment aid mixture that significantly improved the dispersibility of cells detached from the microspheres, enhancing the efficiency of thermosensitive cell detachment by approximately 40%. The harvested UC-MSCs retained their capacity for re-proliferation and trilineage differentiation. Consequently, the temperature-responsive microspheres developed in this study, combined with the cell detachment aid mixtures, hold great potential for large-scale culture and harvesting of therapeutic cells in clinical applications.

Use of the Pickering Emulsion Method for the Preparation of Nano‐Aluminum Powder/Fluororubber Composite Microspheres

AbstractThe combination of fluoropolymer and nano‐thermite has been a research focus in the field of materials in the field of energy and storage in recent years, but it faces the problem of uneven mixing of fluoropolymer and nano‐aluminum powder (nAl). Therefore, it is of great significance to obtain a fluorine/aluminum uniform composite by a solid/solid phase mixing method. In this paper, Pickering emulsions effectively blend difficult‐to‐mix powders of nAl and solid bulk fluoroelastomers on the micro‐ and nanoscale. The emulsion was prepared by Pickering emulsion with an ethyl acetate solution of fluororubber as the oil phase and perfluorocarboxylic acid‐modified nano‐aluminum powder as a surfactant. The effects of oil/water ratio, fluororubber/aluminum ratio, and standing time on the stability of the emulsion were studied. The nano‐aluminum powder/fluororubber composite microspheres were prepared and their morphology, thermal decomposition, and combustion properties were characterized. The results showed that the emulsion prepared with the oil/water ratio of 1:8 and m(fluororubber):m(modified nano‐aluminum powder) of 5:1 had good stability and dispersion. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) results showed that the complex was observed to be regular spherical and the size was about 10 µm, and the composite microspheres prepared by the Pickering emulsion had good. The TG‐DSC results showed that the decomposition of the composite microspheres started at about 450 °C and finished at 519 °C. The composite microspheres prepared in this paper are stable and rapid in exotherm, with a combustion rate of 33 cm s−1 and excellent combustion performance. The Pickering emulsion introduces a new idea for the preparation of thermite by mixing the solid reactants at the micro‐nano level without introducing substances that reduce the energy of the system.

Fixation behavior of oceanic manganese nodule-sodium alginate composite microspheres for heavy metal release during manganese nodule mining

Research on the environmental impact of deep-sea mining is crucial, particularly for fragile deep-sea ecosystems. This research focuses on the issue of heavy metal release during mining activities. Through simulation experiments, we investigated the release of Cu2+, Co2+, and Ni2+ from sediments under disturbance conditions and the fixation behavior during the deployment of ocean manganese nodule-sodium alginate composite microspheres (OMN@SA). The experimental results revealed that mining disturbances cause the release of 0.291% of Cu2+, 7.34% of Co2+, and 4.13% of Ni2+ from sediments into the water, primarily in the form of exchangeable metals. Compared with the bottom adsorption, OMN@SA has a faster adsorption rate in the slow settling process. The removal rates of Cu2+, Co2+ and Ni2+ reached 54.0%, 78.3% and 61.8% for 5 h adsorption, and the bottom adsorption removal rates reached 96.4%, 97.8% and 95.1% for 30 d adsorption, which has a good removal effect. In addition, OMN@SA can effectively block the diffusion of Cu2+, Co2+, and Ni2+ from interstitial water to overlying water, and reduce the influence of interstitial water on overlying water. SEM-EDS, FTIR, and XRD analyses revealed that OMN@SA adsorbs heavy metal ions through its abundant -OH groups and incorporates Cu2+, Co2+, and Ni2+ into the crystal lattices of vernadite and todorokite via substitution or intercalation. This study provides guidance for the remediation of heavy metal release from deep-sea mining using adsorption methods and demonstrates the promising application prospects of OMN@SA.

A size-switchable microsphere loaded with salmon calcitonin as two-weekly dosing for osteoporosis therapy

Osteoporosis is a disease with an increased incidence of fractures due to decreased bone mass and destruction of the microstructure of bone tissue. Salmon calcitonin (sCT), as a peptide, possesses the ability to inhibit osteoclast activity and thus regulate bone metabolism in clinical. However, short half-life and unstable physicochemical properties leading to rapid degradation of sCT have severely limited its clinical application. In this study, a size-switchable microsphere was developed to solve the problem of frequent administration and poor stability of sCT. sCT was encapsulated into Egg PC to form anhydrous reverse micelles (ARM) and then ARM was encapsulated into microspheres (MS@ARM). The degradable composite microspheres were utilized to provide a drug reservoir for sustained release of ARM encapsulated with sCT to reduce the frequency of drug administration, while the released ARM encapsulated with sCT entered the blood circulation to further protect sCT. In vitro release experiments demonstrated that the microspheres could sustain the release of sCT for at least 16 days. The microspheres MS@ARM showed the advanced therapeutic effect on the mouse model of glucocorticoid-induced osteoporosis (GIOP) at a low dosing frequency. The size-switchable microsphere is expected to be a new strategy for delivering sCT for osteoporosis treatment.

Adsorption and detection of praseodymium ion by ion-imprinted polymer with ultra-low sensitivity.

A novel kind of carbon dot (CD) was prepared by one-step hydrothermal microwave assisted method using L-tryptophan and L-tartaric acid as raw materials. Monodisperse poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) microspheres were utilized as the matrix, with praseodymium (Pr) ion (Pr3+) as the template, methacrylic acid as the functional monomer, and 5-amino-8-hydroxyquinoline (5-AHQ) acts as the ligand. A composite microsphere of ion-imprinted polymer (IIP) and CD (noted CD@IIP) was prepared by surface-initiated atom transfer radical polymerization (SI-ATRP). For comparison, IIP without CD (Pr-IIP) and non-imprinted polymer (NIP) were also prepared. Through static adsorption experiments, it was determined that the saturated adsorption amount of CD@IIP is 47.19mgg-1, that of Pr-IIP is 54.49mgg-1, while that of NIP is only 24.32mgg-1. Dynamic adsorption experiments showed that the equilibrium of three kinds of materials wasreached within 30min. Particularly, CD@IIP could emit two fluorescence peaks at 325nm and 421nm under ultraviolet irradiation, and exhibited excellent selectivity and fluorescence quenching effect on Pr3+. The fluorescence response of Pr3+ in the range 0-400μmol L-1 was determined by ratiometric fluorescence method, offering a two-stage model and robust linear regression coefficient. These results demonstrated that CD@IIP exhibited selective adsorption ability for Pr3+, and a sensitive, rapid and simple method for detection of Pr3+ was successfully developed.

Enhanced Photothermal-Assisted Hydrogen Production via a Porous Carbon@MoS2/ZnIn2S4 Type II-S-Scheme Tandem Heterostructure.

MoS2/ZnIn2S4 flower-like heterostructures into porous carbon (PC@MoS2/ZIS) are embedded. This ternary heterostructure demonstrates enhanced light absorption across a broad spectral range from 200 to 2500nm. It features both Type-II and S-scheme dual heterojunction interfaces, which facilitate the generation, separation, and transfer of photoinduced carriers. The PC enveloped by MoS2/ZIS composite microspheres serves as a photothermal source, providing additional energy to the carriers. This process accelerates charge separation and migration, enhancing photothermal-assisted photocatalytic H2 evolution. The optimal H2 evolution rate for PC@MoS2/ZIS reaches an impressive 18.79mmolg-1h-1, with an apparent quantum efficiency of 14.1% at 400nm. This work presents a promising approach for effectively integrating multicomponent heterostructures with photothermal effects, offering innovative strategies for efficient solar energy utilization and conversion.

Covalent organic framework-derived C@COF core-shell microspheres for electrocatalytic hydrogen evolution

Although hydrogen represents a vital source of clean energy, the development of cost-effective, durable materials for use as catalysts in the hydrogen evolution reaction (HER) remains a challenge. In this work, covalent organic framework (COF) - derived core-shell microspheres were prepared as novel electrocatalysts. The previously prepared COF microspheres were pyrolyzed into nitrogen-doped porous carbon (N–C) as the core for enhanced electrocatalytic conductivity. With the assistance of a dual-ligand, the COF shell grew on the surface of N–C to form a core-shell microsphere, which was named N–C@COF. The surface morphology and core-shell structure of N–C@COF were characterized by SEM and TEM. FT-IR, TGA, and XPS were utilized to ascertain the synthesis of COF and the composition of the core-shell microspheres. The N–C@COF core-shell microspheres exhibited excellent HER performance in 1 M KOH electrolyte, demonstrating a low overpotential of 104 mV @ 10 mA cm−2, significantly outperforming pure COF and N–C. Furthermore, the N–C@COF demonstrated excellent HER stability over a 24 h period and retained its HER activity following 2000 consecutive cycles of electrolysis. The presence of the N–C core in the N–C@COF enhanced the electrical conductivity of the catalyst, while the COF shell provided abundant active sites for the HER, resulting in a synergistic improvement in the catalytic efficiency. This work presents a straightforward strategy for synthesizing COF-based multicomponent core-shell microspheres, which provides a promising pathway for the development of available and cost-effective electrocatalysts.

Amidation modified hollow composite microspheres as a self-floating adsorbent for efficient capture of anionic dye DB86 and heavy metal nickel (II).

The co-contamination of dyes and heavy metal ions often used as mordants poses potential risks to environment and public health, and is a challenging problem that needs to be solved in water treatment. Meanwhile, improving the solid-liquid separation capability of adsorbents is of great significance for the application of adsorption technology. Herein, amidation modified hollow composite microspheres were prepared using hollow glass microsphere (HGM) as matrix through hydrolysis and condensation of silane coupling agent (A-1100) and subsequent amidation reaction. The material (HGMNE) not only exhibited good adsorption performance for DB86 and Ni2+ but also had stable self-floating capability. The adsorption of DB86 by HGMNE is mainly carried out by the electrostatic interaction between positively charged quaternary amine nitrogen and negatively charged DB86, while the adsorption of Ni2+ is achieved by the carboxyl group in EDTA group through complexation interaction to adsorb Ni2+ to form Ni complex. This research not only is devoted to the utilization of HGMNE to achieve the co-removal of DB86 and Ni2+ and flexible self-floating solid-liquid separation but also verifies the feasibility and applicability of the modification method of introducing organic adsorption functional groups through amidation reaction, so as to expand the preparation path of HGM-based adsorbents.

Fabrication of ZMF@PS composite microspheres as T2 contrast agents with enhanced contrast performance and magnetic properties

The impacts of nanoplastics on the environment and organisms are gradually increasing, using MRI to detect the metabolic pathways of nanoplastics has low sensitivity and requires magnetic particles for enhanced visualization. In this study, we used Mn0.6Zn0.4Fe2O4 nanoparticles as magnetic particles and coated them with polystyrene to afford polystyrene composite microspheres (ZMF@PS) with enhanced contrast performance. The effects of the polymerization parameters on the morphology and loading rate of the magnetic ZMF@PS composite microspheres were investigated. In addition, the effect of the magnetic contrast agent (ZMF particles) on the magnetic properties of the ZMF@PS composite microspheres was examined. The results show that when MAA and KPS quantities are 1 mL and 0.02 g, respectively, ZMF was uniformly distributed in the ZMF@PS composite microspheres exhibiting a good coating effect, with an average microsphere size of only 151.09 nm. Regarding the contrast performance, an increase in the ZMF content increased the loading rate, saturation magnetization intensity, and relaxation rate of the ZMF@PS composite microspheres.

Preparation of microstructure controllable CL-20/FOX-7 composite microspheres by microchannel recrystallization technology to enhance safety and combustion performance

Realizing the balance between high energy density and multifunctionality of energetic materials is a hot spot in current research, and its study is of great significance for the application of energetic materials. Regulating microstructure is widely recognized as an effective strategy for solving such problems. In this paper, four different microstructures of Hexanitrohexaazaisowurtzitane(CL-20)/1,1-diamino-2,2-dinitroethylene(FOX-7) composite microspheres, namely, hollow, porous irregular microspheres, porous microspheres, and layered porous microspheres, were prepared by microchannel recrystallization technology. The effects of crystal precipitation rate, binder mechanical properties, and purity of water phase on the microstructure of composite microspheres were systematically investigated. The four prepared samples were spherical particles with regular morphology and uniform particle size. The angle of repose and mechanical sensitivity tests showed that the CL-20/FOX-7 composite microspheres had good dispersibility and mechanical sensitivity. Ignition experiments show that hollow microspheres have the best energy release efficiency, while porous microspheres have higher energy density and more stable energy release efficiency. The results show that the combustion performance and safety of the composite microspheres can be effectively enhanced by adjusting the microstructure. Microchannel recrystallization technology can realize the controllable preparation of the microstructure of composite microspheres, which provides a reference for the design and preparation of other composite microspheres.

Application of Mg-MOF-loaded gelatin microspheres with osteogenic, angiogenic, and ROS scavenging capabilities in bone defect repair

The management of bone defects, particularly those with irregular geometries resulting from osteoporotic fractures, remains fraught with challenges. Microspheres have emerged as a promising vehicle for tissue engineering, distinguished by their controlled release, safety, and ease of application. Various bioactive components are integrated into microspheres to improve their performance. Metal-organic frameworks, formed from metal ions interconnected by organic ligands, are increasingly utilized in tissue engineering. Specifically, magnesium-based MOFs are notable for their broad applicability; Mg2+ ions are instrumental in bone reconstruction and repair, facilitating osteogenesis, angiogenesis, antibacterial effects, and anti-inflammatory properties. Mg-MOF was synthesized using magnesium chloride and gallic acid, and it was incorporated into gelatin microspheres to create Gel@Mg-MOF composite microspheres. Leveraging gelatin's biocompatibility, controlled release, and biodegradability, the composites' biocompatibility was evaluated through toxicity and adhesion assays. Moreover, the osteogenic and angiogenic potentials of the Gel@Mg-MOF microspheres were assessed, alongside their capacity for ROS scavenging. Results suggest that controlled Mg2+ release from Gel@Mg-MOF microspheres promotes osteogenic activity in RBMSCs and enhances angiogenic potential in HUVECs. Additionally, the gallic acid-containing composite microspheres exhibited antioxidative properties. Collectively, the findings suggest that Gel@Mg-MOF microspheres could provide effective support for bone defect repair, with potential for clinical deployment.

Dual cytokine release from microsphere-containing decellularized extracellular matrix immune regulation promotes bone repair and regeneration

Most bone filler materials currently achieve bone regeneration by mimicking the natural bone extracellular matrix. However, it is difficult for these materials to replicate the structural functions and bioactivities, including immunomodulation, of natural bone perfectly to reduce inflammation and promote bone regeneration synergistically. Repairing bone defects with scaffolds using a decellularised extracellular matrix (dECM) as a matrix material is an important clinical application and research direction. Here, we processed bovine cancellous bone via an optimised combination of decellularisation methods and preferred dECM, which has the shortest processing time and lowest immunogenicity. Hexagonal mesoporous silica (HMS)/poly(lactic-co-glycolic acid) (PLGA) microspheres loaded with bone morphogenetic protein-2 (BMP-2) were prepared using the complex emulsion method. The HMS/PLGA microspheres had longer cytokine release periods than did the separate HMS and PLGA microspheres. Composite BMP-2/HMS/PLGA microspheres were used to prepare dual-loaded cytokine scaffolds with bone immunomodulatory capacity, which were prepared from composite BMP-2/HMS/PLGA microspheres to increase the osteogenic activity of the dECM and to adsorb interleukin-4 (IL-4) on the surface of the scaffolds. The results showed that the dECM had good cytocompatibility and mechanical strength, and the composite microspheres and IL-4 further endowed the dECM with an ordered spatiotemporally controlled release function, which could release BMP-2 for more than 4 months in the long term and release IL-4 for approximately 10 days in the short term. The composite scaffold not only effectively promoted the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) but also immunomodulated the M1 to M2 polarisation of macrophages (MPs) and mediated the M2 polarisation of MPs, which in turn promoted the osteogenic differentiation of BMSCs, creating a favourable immune microenvironment for bone regeneration. In vivo, the dual drug-loaded scaffolds also exhibited good biocompatibility and significantly superior immunomodulatory bone-enhancing properties compared with those of the other groups. In summary, the combination of dECM scaffolds with cytokine-carrying microspheres and immunomodulatory factors can promote the orderly spatiotemporal release of cytokines, which significantly enhances the bone regeneration and repair effects of dECM scaffolds and is a promising bone filler material for clinical application.

Predicting effective thermal conductivity of HGM composite using ML

Data-driven materials research can be used as an effective tool to supplement conventional approaches in designing new materials. Hollow glass microsphere (HGM) composites are widely used for high-temperature thermal insulation applications, and their synthesis is traditionally done by varying parameters of the constituents on a trial-and-error basis. In this work, a prediction tool based on a supervised machine learning (ML) model is developed to predict the effective thermal conductivity (ETC) of an HGM composite by tailoring the composition and parameters of the constituents to reduce the time and cost involved. A comprehensive database containing the various input features is generated from previous experimental investigations conducted on various HGM composites. ML models, namely random forest regression (RF), K-nearest neighbor (KNN), support vector regression (SVR), and artificial neural network (ANN), are used to predict the ETC of HGM composites. Feature importance analysis showed that the matrix material’s thermal conductivity and the composite’s bulk density have the highest impact on the ETC of the HGM composite, followed by porosity and average microsphere size. ANN emerged as the best model to predict HGM composite ETC with the lowest root mean square error and highest R2 value for predictions. Moreover, a systematic approach for key feature selection using ANN shows that adding or omitting additional features beyond an optimal combination degrades the model’s predictive accuracy.

A novel kind of hollow SiO2@g-C3N4@TiO2 microspheres for rapid removal of dyes and antibiotics in water under sunlight

In this paper, using PVP-modified polystyrene microspheres as template, tetrabutyl titanate (TEOT), tetraethyl orthosilicate (TEOS) and melamine as precursor, we developed a facile one-pot two-step method to preparing a novel kind of mesoporous hollow SiO2@TiO2@g-C3N4 ternary composite microspheres with plush surface, in which highly active black titanium dioxide (TiO2) was formed by simple calcination without further chemical reduction treatment. The structure and morphology of the composite microspheres were detailed characterized for understanding the formation mechanism. Research results indicated that the hollow SiO2 microspheres can promote the formation of oxygen vacancies in TiO2, and the ternary combination narrowed the bandgap width of the black hollow composite microspheres to 1.43 eV, thus endowing it with excellent broad-spectrum catalytic performance for rapid photo-degradation of persistent organic pollutants (POPs) such as dyes and antibiotics in water under sunlight. The removal rates of dyes reached more than 70 %, as well as that of antibiotics more than 50 % within one hour. Finally, a plausible catalytic degradation mechanism was discussed.

Hydrogel Microsphere-Encapsulated Bimetallic Nanozyme for Promoting Diabetic Bone Regeneration via Glucose Consumption and ROS Scavenging.

The healing of bone defects among diabetic patients presents a critical challenge due to the pathological microenvironment, characterized by hyperglycemia, excessive reactive oxygen species (ROS) production, and inflammation. Herein, multifunctional composite microspheres, termed GMAP are developed, using a microfluidic technique by incorporating Au@Pt nanoparticles (NPs) and GelMA hydrogel to modulate the diabetic microenvironment for promoting bone regeneration. The GMAP enables the sustained release of Au@Pt NPs, which function as bimetallic nanozymes with dual enzyme-like activities involving glucose oxidase and catalase. The synergistic effect allows for efficient glucose consumption and ROS elimination concurrently. Thus, the GMAP effectively protects the proliferation of bone marrow mesenchymal stem cells (BMSCs) under adverse high-glucose conditions. Furthermore, it also promotes the osteogenic differentiation and paracrine capabilities of BMSCs, and subsequently inhibits inflammation and enhances angiogenesis. In vivo diabetic rats bone defect model, it is demonstrated that GMAP microspheres significantly improve bone regeneration, as verified by micro-computed tomography and histological examinations. This study provides a novel strategy for bone regeneration by modulating the diabetic microenvironment, presenting a promising approach for addressing the complex challenges associated with bone healing in diabetic patients.

Incorporation of carboxymethyl chitosan (CMCS) for the modulation of physio-chemical characteristics and cell proliferation environment of the composite hydrogel microspheres

Hydrogels have excellent swelling properties and have been widely applied in tissue engineering because of their similarity to the extracellular matrix (ECM). Sodium alginate (SA) and carboxymethyl chitosan (CMCS) were prepared into hydrogel microspheres with Ca2+crosslinking in our study. The morphology, inner structure, mechanical properties, water content, swelling rate and BMP-2 loading and releasing properties were characterized. Our results showed that the composite SA /CMCS hydrogel microspheres were translucent and spherical in shape with uniform particle size. The incorporation of CMCS further increased the diameters of the microspheres, internal pore structure, water content, and mechanical properties of the SA/CMCS hydrogel microspheres. At the same SA concentration, with the increase of CMSC concentration, the diameter of microspheres could be increased by about 0.4 mm, the water content can be increased about 1%-2%. As for the mechanical properties, the compressive strength can be increased by 0.04-0.1 MPa, and the modulus of elasticity can be increased by 0.1-0.15 MPa. BMP-2 was chosen as a model agent and it could be loaded into SA/CMCS microspheres, and the incorporation of CMCS increased BMP-2 loading. The encapsulated BMP-2 was sustainably releasedin vitro. The leaching solutions of the SA/CMCS hydrogel microspheres exhibited good cytocompatibility and could increase ALP activity, ALP expression, and biomineralization on MC3T3-E1 cells. After 7 d of co-culture, ALP activities in S2.5C2 and S2.5C3 groups was increased by 50% and 45% compared with that of the control group. When embedded in the SA/CMCS microspheres, the MC3T3-E1 cells were evenly distributed inside the hydrogel microspheres and remained viable. Transcriptomic studies showed that incorporation of CMCS induced upregulation of 1141 differentially expressed genes (DEGs) and downregulation of 1614 DEGs compared with SA microspheres. The most significantly enriched pathways were the Wnt and MAPK signaling pathways induced by the incorporation of CMCS and BMP-2. In conclusion, our results indicated that the physiochemical characteristics of the SA hydrogel microspheres could be greatly modulated by CMCS to better mimic the ECM microenvironment and induce osteo-inductive activities of MC3T3-E1 cells.