Cross-linked Chitosan Microspheres Research Articles

SPRAY-DRIED CHITOSAN MICROSPHERES FOR SUSTAINED DELIVERY OF TRIFLUOPERAZINE HYDROCHLORIDE: FORMULATION AND IN VITRO EVALUATION

Objective: Sustained release systems have the potential to enhance the therapeutic responses in the long-term management of psychiatric disorders. In the present study, cross-linked microspheres of the antipsychotic drug Trifluoperazine (TFP) were prepared using biodegradable polymer-chitosan and various in vitro evaluations were performed on the prepared microspheres. Methods: The spray drying technique was used to prepare TFP-loaded chitosan microspheres. Tripolyphosphate (TPP) was incorporated into the chitosan solutions as a cross-linking agent in varying concentrations. Different evaluations like production yield, encapsulation efficiency, drug-polymer compatibility, Scanning Electron Microscopy (SEM), X-ray diffraction studies (XRD), Differential Scanning Colorimetry (DSC), particle size, zeta potential analysis and in vitro drug release studies were performed on the developed formulations. Results: The formulated microparticles exhibited production yields ranging from 38.51 to 57.21% and had reasonably good encapsulation efficiencies (54.52-78.35%). The drug excipient compatibility was confirmed by Infrared Spectroscopy. All the microspheres showed positive zeta potential with a mean diameter ranging from 1.45-3.61µ. SEM images revealed the formation of spherical particles with indentations on the surface. XRD and DSC studies confirmed the presence of an amorphous form of the drug inside the microspheres. The in vitro release profile of TFP from cross-linked chitosan microspheres was influenced considerably by changing the concentration of polymer and crosslinking agent in the formulation. The drug release from (0.5%) chitosan microspheres reduced from 91% to 79%, when TPP concentration was increased from 10% w/w to 30% w/w. All the formulations clearly showed a burst release of the drug in the initial hours and a subsequent sustained release profile. Conclusion: The results of this study suggest that TPP crosslinked spray-dried chitosan microparticles could be a promising method for developing a long-acting drug delivery system intended to effectively treat schizophrenia.

Yb(OTf)3 Anchored on Crosslinked Chitosan Microsphere: A Green Heterogenized Catalyst for the Synthesis of Bispiro‐Fused Heterocycles

AbstractUsing renewable biomass chitosan as a raw material, crosslinked chitosan microsphere (CCM) was prepared by inverse suspension, which was then immersed in the ethanol solution of Yb(OTf)3 to fabricate CCM‐supported Yb(OTf)3 (Yb(OTf)3@CCM). The three‐component [3+2] cycloaddition of isatins, tetrahydroisoquinolines and 5‐alkenyl rhodanines was developed with Yb(OTf)3@CCM as a green heterogeneous catalyst, which gave access to a suite of architecturally complex bispiro‐fused heterocycles merging four pharmacophores with moderate to excellent yields (50–96 %) and diastereoselectivities (up to 99 : 1 dr). The reaction mechanism was preliminarily clarified by controlled experiments and dynamic high‐resolution mass spectrometry studies. The synthetic potential of this protocol was proved by a gram‐scale reaction which furnished the product with comparable results (85 % yield and 72 : 28 dr). Moreover, the catalyst could be recovered just through filtering, washing and drying process, and reused five times with the catalytic activity remaining in an acceptable range (from 93 % to 73 % yield).

Removal of BB41 dye molecules onto cross-linked chitosan microspheres: synthesis, characterization, and sorption/desorption

Removal of BB41 dye molecules onto cross-linked chitosan microspheres: synthesis, characterization, and sorption/desorption

Chitosan grafted with crown ether with high selectivity and adsorption on lithium-ion

Currently, Lithium is the lightest metal known in nature, which is widely applied in most walks of life. However, the present storage of lithium resources in the world is far from meeting the consumption market surge demand for lithium resources. Liquid lithium resources such as Salt Lake brine and seawater brine will become the primary source and inevitable choice for lithium extraction in the future due to a large amount of lithium, and its recovery requires a simple and effective process. This study synthesized TEG4MEC, a pseudo-crown ether monomer with a ring unit, to achieve effective Lithium-ion (Li+) recognition through specific interaction with Li+. Then, the TEG4MEC monomer was grafted onto the surface of cross-linked chitosan microspheres (CCS) by surface initiation polymerization. A series of static and dynamic adsorption studies showed that the pH value of the solution had a significant effect on Li+ adsorption. For CCS-TEG4MEC microspheres, the best adsorption effect was observed at pH = 7.0. The maximum adsorption capacity of Li+ on CCS-TEG4MEC microspheres obtained by Langmuir isotherm fitting is 156.16 mg g−1. In addition, CCS-TEG4MEC microspheres also showed effective regeneration performance and highly stable adsorption capacity, which could be reused.

Preparation and Characterization of Vanillin Cross-linked Chitosan Microspheres Modified by Silver Nanoparticles

In this work, the vanillin cross-linked chitosan microspheres were firstly prepared by emulsion chemical cross-linking method with vanillin as a cross-linker. Subsequently, with polyvinylpyrrolidone as a nanoparticle stabilizer and dispersant, silver nanoparticles were modified onto the surface of vanillin cross-linked chitosan microspheres by in situ reduction with ascorbic acid to obtain silver nanoparticles modified microspheres. The chitosan and two kinds of microspheres were characterized by SEM, FTIR and XRD. The SEM images showed that the two kinds of microspheres had clear and well-defined spherical shapes with an average particle size of 4.2 μm and the silver nanoparticles were then evenly dispersed on the surface. The FTIR spectra revealed that chitosan was successfully cross-linked by vanillin through Schiff base reaction and hydrogen bond interactions. The X-ray diffraction pattern of vanillin cross-linked chitosan microspheres modified with silver nanoparticles indicated that the silver nanoparticles had a face-centred cubic structure with an average particle size of 44.4 nm confirmed by SEM, which proved the successful synthesis of target composite microspheres.

Preparation of a novel CSM@ZIF-67 composite microsphere to facilitate Congo red adsorption from dyeing wastewater

ABSTRACT Chitosan (CS) is commonly used as an adsorbent for wastewater treatment because of its low cost, strong adsorption properties, and high availability of raw materials required for its production. However, CS exhibits limited adaptability to pH, poor mechanical properties, and high swelling in aqueous media; these limitations restrict its widespread use. To address these issues, herein, zeolitic imidazolate framework-67 (ZIF-67) is loaded onto crosslinked CS microspheres (CSM) to prepare CSM@ZIF-67, a composite adsorbent. Next, the CSM@ZIF-67 is applied to the treatment of Congo red (CR) dye, which is typically present in printing and dyeing wastewater. The results demonstrate that the in situ synthesis of metal-organic frameworks (MOFs) on CSM improve the dispersion of MOFs and preserve the morphology of the MOFs. The adsorption equilibrium of CSM@ZIF-67 is reached within 150 min, and its adsorption capacity is as high as 538.4 mg/g at a pH of 9 and temperature of 25 °C. The CR adsorption process is consistent with the pseudo-second-order kinetic and Langmuir isotherm models, thus revealing that chemisorption is the primary rate-limiting step, and the pollutants are adsorbed on the adsorbent surface in a monolayer. Experiments on material cycling and regeneration performance reveal that the removal efficiency of CSM@ZIF-67 remains above 90%, even after five rounds of adsorption. CSM@ZIF-67 has abundant functional groups and adsorption sites and can efficiently remove CR through mutual interactions between the metal coordination effect, π–π conjugation, hydrogen bonding, and electrostatic interactions.

Degradation-Dependent Controlled Delivery of Doxorubicin by Glyoxal Cross-Linked Magnetic and Porous Chitosan Microspheres.

Glyoxal cross-linked porous magnetic chitosan microspheres, GMS (∼170 μm size), with a tunable degradation profile were synthesized by a water-in-oil emulsion technique to accomplish controlled delivery of doxorubicin (DOX), a chemotherapeutic drug, to ensure prolonged chemotherapeutic effects. The GMS exhibit superparamagnetism with saturation magnetization, Ms = 7.2 emu g–1. The in vitro swelling and degradation results demonstrate that a swelling plateau of GMS is reached at 24 h, while degradation can be modulated to begin at 96–120 h by formulating the cross-linked network using glyoxal. MTT assay, live/dead staining, and F-actin staining (actin/DAPI) validated the cytocompatibility of GMS, which further assured good drug loading capacity (35.8%). The release mechanism has two stages, initiated by diffusion-inspired release of DOX through the swollen polymer network (72 h), which is followed by a disintegration-tuned release profile (>96 h) conferring GMS a potential candidate for DOX delivery.

Optimization of synthesis of geopolymer adsorbent for the effective removal of anionic surfactant from aqueous solution

This paper describes the optimization of synthesis of fly ash based geopolymer (FAGP) for removing the anionic surfactant sodium dodecylbenzene sulfonate (SDBS) using response surface methodology (RSM) by varying the synthesis parameters of silica to alumina (Si/Al), sodium to alumina (Na/Al) and water to solid (W/S) ratios with the adsorption capacity as the response. The geopolymer samples were designed, synthesized, characterized, used for removing SDBS surfactant, and regenerated. Surface area and pore size analysis, Fourier Transform Infrared Spectroscopy (FTIR) analysis, phase analysis, and microstructural analysis confirmed the synthesis of mesoporous and amorphous geopolymers with the presence of pores, cavities and rods in the geopolymer structure. Geopolymer sample synthesized with the composition of Si/Al-2.87, Na/Al-1.0 and W/S-0.35 (FAGP-2) achieved maximum surface area of 59.512 m2/g and displayed the highest adsorption capacity of 743.706 mg/g and removal efficiency of 84.5%. The ANOVA analysis showed a correlation coefficient (R2) of 0.952, F-value of 22.27, and p value of 0.05 which indicated the significance of the model and lack of fit was non-significant which showed good fitting of the experimental data to the quadratic model with 95% confidence level. The proposed geopolymer composition of Si/Al-2.353, Na/Al-1.056, and W/S-0.339 achieved adsorption capacity of 730.212 mg/g which is 99% similar to the predicted adsorption capacity. Thermal method successfully regenerated SDBS adsorbed geopolymer with only 13.8% loss of adsorption capacity after five cycles of regeneration. The adsorption capacity of optimized geopolymer is higher than other adsorbents such as cross-linked chitosan films, commercial activated carbon, surface functionalized mesoporous silica nanoparticles, multi-walled carbon nanotubes (MWCNTs), and others used for removing SDBS surfactant and only amino crosslinked chitosan microspheres (ACCMs) has higher adsorption capacity than geopolymer. This shows that geopolymer can also be effectively used to adsorb SDBS surfactant from wastewater.

Hexametaphosphate cross-linked chitosan beads for the eco-efficient removal of organic dyes: Tackling water quality

There is an increasing trend of developing various low-cost grafted natural amino polysaccharides for the biosorptive removal of noxious dye effluents like Malachite green (MG) and anionic Reactive Red–195 (RR-195) dyes from aqueous solution. Chemically cross-linked chitosan microsphere (CTS-HMP), a promising non-toxic biosorbent possessing high charge density and thermal stability was prepared by using hexametaphosphate as ionic cross-linker. Batch biosorption experiments were carried out under different temperatures (298, 308 and 318 K), pH (2.0–10.0), initial concentrations (25–250 mg L−1), adsorbent dosage (0.01–0.1 g) and contact times (0–180 min) to understand the optimum experimental conditions and simultaneously evaluate the adsorption isotherms and kinetics of CTS-HMP. Biosorption equilibrium was established in 120 and 60 min for MG and RR-195 removal process. The pseudo-equilibrium process was best described by the pseudo-second-order kinetic (R2 ≥ 0.98), Freundlich and Temkin isotherm model (R2 ≥ 0.90). The removal rate of MG and RR-195 gradually increased (69.40 and 148 mg g−1) at 250 mg L−1 of initial concentration till 100 and 50 min of contact period in a single contaminant system, though the removal efficiency of acid dye was ~2 times higher compared to basic dye under optimum conditions (p < 0.05; t-test). Thermodynamic parameters indicated exothermic (MG) and endothermic (RR-195) nature of spontaneous dye removal. The activation energy of sorption (Ea) was <50 kJ mol−1 which highlighted the importance of physical adsorption process. Therefore, the obtained results clearly validate the sustainable utilization of CTS-HMP as a promising functionalized chitosan microparticles/agent for removing dye effluents from the contaminated aqueous phase.

Mebeverine Hydrochloride Loaded Chitosan Microspheres as Potential Treatment Targeting Irritable Bowel Syndrome: Box-Behnken Design Optimization

Objective: Mebeverine hydrochloride is an antispasmodic agent that has a direct musculotropic action on the smooth muscles of the gastrointestinal tract; especially the colon.Therefore, the current study aimed at formulating and optimizing colon targeted mebeverine hydrochloride microspheres for treatment of chronic gastrointestinal disorder. Methods: Mebeverine hydrochloride-loaded chitosan microspheres were formulated adopting emulsion cross-linking method using glutaraldehyde as a cross linking agent. A 33 Box Behnken design was utilized in formulating the microspheres and investigating the effect of different formulation factors such as drug: polymer ratio (X1), stirring speed (X2) and the surfactant concentration (X3) on particle size (Y1), the entrapment efficiency percentage (Y2) and the cumulative release percentage of mebeverine hydrochloride after 8 h (Y3). Results: The particle size and entrapment efficiency were significantly affected by tested formulation parameters. The release of mebeverine hydrochloride from optimized formula was pH dependent. In simulated gastric fluid, less than 10% of entrapped mebeverine hydrochloride was released, while, a relatively high amount of the drug (> 65%) was released in simulated colonic fluid (pH 7.4). The in vivo pharmacokinetic study revealed that the optimized formula of microspheres exhibited increased oral absorption of mebeverine hydrochloride, compared to free drug (Cmax 168.51±20.05 ng/ml vs. 126.45±29.46 ng/ml, respectively). In addition, the optimized formula exerted a remarkably higher systemic bioavailability, compared to the free drug. Conclusion: These results underscore the applicability of cross-linked chitosan microspheres as a promising carrier for colon targeted delivery of mebeverine hydrochloride for treating diseases associated with the colon such as irritable bowel syndrome.

Preparation of sulfonate chitosan microspheres and study on its adsorption properties for methylene blue

Dyes bring a lot of benefits to our lives, however, as common organic pollutants, they have destructive influences on the environment. Firstly, glutaraldehyde crosslinked chitosan microspheres (GCS) are prepared via inverse-phase suspension polymerization. Then, GCS microspheres are acted as the base material, ammonium persulfate (Aps) as the initiator, sodium styrene sulfonate (SSS) as anionic functional monomer, functional microspheres (GCS-g-PSSS) are prepared by surface grafting polymerization. The amount of monomer and Aps, temperature and reaction time is respectively explored. The chemical structures and physicochemical properties of functional microspheres were characterized by FT-IR, zeta potential, scanning electron microscope and X-ray photoelectron spectroscopy. The adsorption kinetic at different temperature and initial concentration is studied and fitted. The adsorption isotherms of GCS-g-PSSS for MB are explored at different pH, temperature and salinity. The adsorption capacity of GCS-g-PSSS for MB is 820.1 mg/g at 318 K. The adsorption isotherms at different temperature are fitted by Langmuir, Freundlich, Dubinin-Radushkevich and Temkin. Thermodynamic parameters imply that adsorption is a spontaneous and endothermic process. And this adsorbent has good reusability. The adsorption ability of GCS-g-PSSS microspheres is also excellent for other cationic dyes. Thus, GCS-g-PSSS microspheres might serve as a promising adsorbent for contaminated water scavenging.

A new emulsification-crosslinking technique for preparation of physically crosslinked chitosan microspheres

A new emulsification-crosslinking method was developed for the preparation of chitosan microspheres. The new method uses an aqueous alkali–urea solution, instead of the commonly used acidic solvents, to dissolve chitosan. After emulsification, the water-in-oil droplets are solidified by heating, taking advantage of the unique in situ thermal gelling behavior of the alkaline chitosan solution, instead of by crosslinking with a usually toxic crosslinker. The size of the microspheres can be controlled by the concentration of chitosan solution, stirring speed, emulsifier concentration, and the curing temperature. The resulting microspheres are physically crosslinked, instead of chemically crosslinked, and they are ready to dissolve in dilute acetic acid. The resulting chitosan microspheres are non-toxic and can be degraded by lysozyme. Bovine serum albumin, a model protein, can be facilely loaded into the microspheres by adsorption, and then released from the microspheres.

Cross-linked chitosan microspheres entrapping silver chloride via the improved emulsion technology for iodide ion adsorption

Radioactive iodine waste from nuclear plant became the severe environmental problem and led to the public health concern. The cross-linked chitosan adsorbed iodide anions through the electrical attraction, yet performing limited-efficiently. Targeting as the better adsorption, the modified chitosan sorbent as AgCl@CM (silver chloride entrapped in the cross-linked chitosan microspheres) for iodine adsorption was proposed and implemented by chemisorption from AgCl and physisorption from chitosan via the improved emulsion method (emulsions mixing-collision and polymerization). With the broad application from pH 2 to pH 10, the spherical AgCl@CM (from 0.20 g silver nitrate) performed the I127 anions (instead of radioactive iodine) adsorption efficiency of higher than 90 % in 20 min, with the maximum adsorption capacity of 1.5267 mmol/g, well-fitting with the pseudo-first-order model and Sips isothermal model. AgCl@CM also performed I127 adsorption with the significant selectivity relative to Cl−. The micro-spherical AgCl@CM sorbents were therefore prospective-effectively for iodine waste water treatment.

Temperature-dependent mucosal permeation kinetics of stigmasterol microspheres: In vivo mice model antioral candidiasis study.

Evaluation of mucosal permeation of stigmasterol from the glutaraldehyde cross linked chitosan microspheres at increasing experimental temperatures was performed. The activation energy of permeation, partition, and diffusion were estimated to understand the permeation kinetic with respect to the temperature. The formulation depicting least activation energy possessed the increased permeation thresholds of drug at the site of application. The encapsulation efficacy and mucoadhesive strength were found to be directly proportional to the polymer-emulsifier ratio. Decreased intensity in crystallography directed the molecular dispersion of microencapsulated drug. The depleted enthalpic phase transition in thermogram affirmed the stigmasterol encapsulation. The sphericity and the size of microspheres were determined by scanning electron photo micrograph. The in vivo quantification of oral Candida infection with different statistical approach and histopathological observation of infected tongue of mice on treatment with the stigmasterol encapsulated microspheres showed significant anti oral candidiasis activity by reduction of fungal colony count and recovery of papillae, reorganization of basal cell layer and newly formed papillae during 21-28 days of treatment.

Development of a Long-Term Drug Delivery System with Levonorgestrel-Loaded Chitosan Microspheres Embedded in Poly(vinyl alcohol) Hydrogel.

This study reports on the fabrication of a controlled release system for the delivery of levonorgestrel (LNG) for long-term contraception. LNG was encapsulated in chemically cross-linked chitosan (CS) microspheres, and microspheres presented a spherical geometry with a good particle size distribution (polydispersity index (PDI) < 0.1). The LNG-CS microspheres were classified based on their particle size range, <63, 63-125, and 125-300 μm, where the 125-300 μm particles were selected to be incorporated into a physically cross-linked and annealed PVA hydrogel matrix to prolong the drug release. PVA concentrations and the annealing treatment influenced the swelling behavior of PVA hydrogels. Fourier transform infrared (FTIR) spectroscopy indicated that CS was successfully cross-linked through the formation of a Schiff base; the PVA hydrogel was formed through hydrogen bonding without reacting with LNG, which was only physically entrapped, thus maintaining its stability. Differential scanning calorimetry (DSC) showed that freeze-thaw and annealing processes increased the degree of crystallinity in the PVA hydrogel. In vitro drug release assessments for all formulations showed zero order without any burst release. Over a period of 100 days, 34, 27, and 21% of LNG was released from the CS-LNG microspheres in the size ranges < 63, 63-125, and 125-300 μm, respectively, while only 14, 11, and 9% of LNG was released when the CS-LNG microspheres were incorporated into 10, 15, and 20% PVA hydrogels, respectively. The drug release kinetics exhibited both diffusion- and swelling-controlled mechanisms following the Korsmeyer-Peppas model. This work presents a promising delivery system for long-term contraception with controlled zero-order release behaviors.

Thermoresponsive polymer brushes on magnetic chitosan microspheres: Synthesis, characterization and application in oily water of high salinity

Smart microspheres capable of responding to magnetic fields and temperature changes were prepared by encapsulating magnetic nanoparticles into cross-linked chitosan microspheres followed by poly(N-isopropylacrylamide) (PNIPAM) brushes formation on their surfaces (MCM-PNIPAM). The synthetized microspheres were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), thermogravimetry (TG) and differential scanning calorimetry (DSC). While most studies have focused on the graft copolymerization reaction between chitosan and NIPAM to get a soluble particle, the main finding of this study was to improve the lipophilicity of magnetic crosslinked chitosan microspheres with PNIPAM brushes, in order to be used in oily water treatment as a solid adsorbent. The thermoresponsive behavior of MCM-PNIPAM was confirmed by the sharp transition phase on DSC curves. The initial investigation of oil removal efficiency was performed to the synthesized microspheres with values higher than 97% for MCM-PNIPAM above the PNIPAM aggregation temperature.

Dual cross-linked chitosan microspheres formulated with spray-drying technique for the sustained release of levofloxacin

Objective: This study was aimed to develop sustained drug release from levofloxacin (LF)-loaded chitosan (CS) microspheres for treating ophthalmic infections.Significance: Dual cross-linked CS microspheres developed by the spray-drying technique displays significantly higher level of sustained drug release compared with non-cross-linked CS microspheres.Methods: LF-loaded CS microspheres were prepared using the spray-drying technique, and then solidified with tripolyphosphate and glutaraldehyde as dual cross-linking agents. The microspheres were characterized by surface morphology, size distribution, zeta potential, encapsulation efficiency, and drug release profiles in vitro. The drug quantification was verified and analyzed by high-performance liquid chromatography (HPLC). The structural interactions of the CS with LF were studied with Fourier transform infrared spectroscopy. The effect of various influencing excipients in the formulation of the dual cross-linked CS microspheres on drug encapsulation efficiency and the drug release profiles were extensively investigated.Result: The microspheres demonstrated high encapsulation efficiency (72.4 ∼ 98.55%) and were uniformly spherical with wrinkled surface. The mean particle size was between 1020.7 ± 101.9 and 2381.2 ± 101.6 nm. All microspheres were positively charged (zeta potential ranged from 31.1 ± 1.32 to 42.81 ± 1.55 mV). The in vitro release profiles showed a sustained release of the drug and it was remarkably influenced by the cross-linking process.Conclusion: This novel spray-drying technique we have developed is suitable for manufacturing LF-loaded CS microspheres, and thus could serve as a potential platform for sustained drug release for effective therapeutic application in ocular infections.

Cross-linked chitosan microspheres: An efficient and eco-friendly adsorbent for iodide removal from waste water

Radioactive iodine from the nuclear wastes was the significant environmental pollution, causing the health concern. Cross-linked chitosan microspheres (CM) by emulsion polymerization were investigated and proposed as the green and efficient adsorbents to treat iodine wastes via I− and -NH2 attraction. The I127 anions (instead of the radioactive iodine) adsorbed by CM were promising according to adsorbent dosage, pH, co-existing anions and recyclability analyzations through FTIR, SEM, BET and TGA. From pH 4 to 10, CMs maintained the I− adsorption efficiency no less than 95%. The maximum adsorption capacity of I− was up to 0.8792 mmol/g relative to the initial 2 mmol/L I− at pH 5 during 40 min adsorption, well-fitting with Freundlich isotherm model and pseudo-second order kinetic model. Moreover, the CMs after five regenerations maintained almost the same adsorption efficiency, and performed the differently competitive-adsorbed behavior. The CMs thus were prospective adsorbents for the iodide removal from waste water.

Fabrication and drug release behavior of ionically cross-linked chitosan microspheres

The chitosan microspheres were prepared by an emulsion-ionic cross-linking method; the interaction between chitosan and an anionic cross-linker was studied, and the average size, surface morphology, insulin sorption and drug release profile of formulated microspheres were evaluated.

Enhanced Antibacterial Activity of Silver Doped Titanium Dioxide-Chitosan Composites under Visible Light.

Nano titanium dioxide (TiO2) with photocatalytic activity was firstly modified by diethanolamine, and it was then doped with broad spectrum antibacterial silver (Ag) by in situ method. Further, both Ag doped TiO2-chitosan (STC) and TiO2-chitosan (TC) composites were prepared by the inverse emulsion cross-linking reaction. The antibacterial activities of STC composites were studied and their antibacterial mechanisms under visible light were investigated. The results show that in situ doping and inverse emulsion method led to good dispersion of Ag and TiO2 nanoparticles on the cross-linked chitosan microsphere. The STC with regular particle size of 1–10 μm exhibited excellent antibacterial activity against E. coli, P. aeruginosa and S. aureus under visible light. It is believed that STC with particle size of 1–10 μm has large specific surface area to contact with bacterial cell wall. The increased antibacterial activity was attributed to the enhancement of both electron-hole separations at the surface of nano-TiO2 by the silver ions under the visible light, and the synergetic and sustained release of strong oxidizing hydroxyl radicals of nano-TiO2, together with silver ions against bacteria. Thus, STC composites have great potential applications as antibacterial agents in the water treatment field.