Chitosan Solution Research Articles

Reversible Sensing Technologies Using Upcycled TPEE: Crafting pH and Light Responsive Materials towards Sustainable Monitoring.

Multiresponsive materials with reversible and durable characteristics are indispensable because of their promising applications in environmental change detections. To fabricate multiresponsive materials in mass production, however, complex reactions and impractical situations are often involved. Herein, a dual responsive (light and pH) spiropyran-based smart sensor fabricated by a simple layer-by-layer (LbL) assembly process from upcycled thermoplastic polyester elastomer (TPEE) materials derived from recycled polyethylene terephthalate (r-PET) is proposed. Positively charged chitosan solutions and negatively charged merocyanine-COOH (MC-COOH) solutions are employed in the LbL assembly technique, forming the chitosan-spiropyran deposited TPEE (TPEE-CH-SP) film. Upon UV irradiation, the spiropyran-COOH (SP-COOH)molecules on the TPEE-CH-SP film undergo the ring-opening isomerization, along with an apparent color change from colorless to purple, to transform into the MC-COOH molecules. By further exposing the TPEE-CH-MC film to hydrogen chloride (HCl) and nitric acid (HNO3) vapors, the MC-COOH molecules can be transformed into protonated merocyanine-COOH (MCH-COOH) with the simultaneous color change from purple to yellow.

Loofah and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nano-fiber-reinforced chitosan hydrogel composite scaffolds with elderberry (Sambucus nigra) and hawthorn (Crataegus oxyacantha) extracts as additives for osteochondral tissue engineering applications

In recent years, people have had more expectations from the developed technology in medicine, especially in the field of orthopedics and traumatology. Tissue engineers are interested in techniques that benefit from patients’ cells and biomaterials, instead of prostheses and implants. On the other hand, researchers have begun to use various medicinal plants for regeneration and anti-cancer studies. In the present study, we aimed to produce cartilage and bone inductive scaffolds for osteochondral tissue engineering applications with the addition of hawthorn or elderberry extracts. Firstly, wet electro-spun poly (3-hydroxybutyric acid-co-3-hydroxyvaleric acid) fibers were integrated with a loofah mat. Then, they were impregnated into chitosan solution with/without hawthorn or elderberry extract. Composite hydrogel scaffolds were obtained by cross-linking with 0.3% (w/v) genipin. Fabricated scaffolds had more than 90% porosity and showed swelling capacity in the range of 1500–2200%. Based on the in vitro biocompatibility analyses using mesenchymal stem cells (MSCs), all the fabricated scaffolds were found to be biocompatible by WST-1, ALP activity, and GAG content analysis. Also, histological/immunohistochemical analyses showed that hawthorn and elderberry extract addition increased MSCs proliferation and collagen type I and II positivity. Consequently, all the scaffolds showed promising features for osteochondral tissue engineering applications.Graphical abstract

Eco‐friendly chitosan polymer mitigates disease severity and mediates plant resistance against Beet curly top Iran virus in tomato

AbstractA tomato‐infecting virus known as Beet curly top Iran virus (BCTIV) cause a significant disease for tomato plants and several other plant species around the world. Chitosan polysaccharide is a natural biopolymer that has been utilised as an exo‐elicitor to enhance plant defence mechanisms against a variety of plant diseases. This study investigates the efficacy of chitosan in combating BCTIV disease on tomato plants and modulating the host–virus interaction under greenhouse conditions. Twenty‐four hours before the virus inoculation, tomato plants were sprayed with a protective chitosan solution at different concentrations (0.5, 1, 1.5, and 2 mg/mL). Tomato plants were inoculated with a BCTIV infectious clone using an Agrobacterium‐inoculation method. The findings clearly demonstrated a reduction in the severity of the disease in chitosan‐treated plants as compared to Mock‐plants, with the percentage decreasing from 61.53% to 75.28% in 1.5 mg/mL treated plants and from 9.01% to 28.43% in 0.5 mg/mL treated plants. In addition, the utilisation of chitosan has the potential to deactivate the accumulation of BCTIV within the host tissues. The virus accumulation was greatly alleviated in 1, 1.5, and 2 mg/mL‐treated plants by 71.29%, 90.11%, and 93.14%, respectively, and over the mock plants. Furthermore, it was found that chitosan applied at all tested concentrations increased the relative expression and mRNA accumulation of genes related to resistance, including the pathogenesis‐related protein gene PR‐1, the HSP90 gene, and the AGO2a antiviral gene. These genes reached their maximum by 22.9‐, 12.93‐, and 4.44‐fold increases, respectively, over the untreated control. According to gas chromatography–mass spectroscop (GC‐MS) fractionation profile, chitosan increased 28 bioactive metabolic components, such as n‐hexadecanoic acid, heptanone, 1,2‐dimethylbenzene, dicarboxylic acid, and cis‐11‐octadecenoic acid methyl‐ester, to improve metabolic pathways. Results reported here revealed that foliar application of chitosan decreases the rate of the disease severity and virus accumulation in BCTIV‐infected tomato plants. This effect is associated with increased gene expression and defence‐related factors, enhancing tomato resistance to BCTIV infection. Consequently, chitosan treatments could be part of an integrated approach for reducing the severity of BCTIV disease in tomato and other host plants.

Application of hydroxypropyl methylcellulose to improve the wettability of chitosan coating and its preservation performance on tangerine fruits

Hydroxypropyl methylcellulose (HPMC) was employed as an intermediate layer to enhance interfacial interaction between chitosan (CS) coating and tangerine fruits, thereby improving the preservation effect. Owing to the low surface tension of tangerine fruit (26.04 mN/m), CS coating solutions showed poor wetting properties on fruit peels (contact angle > 100°). However, by applying a 1.0 % (w/v) HPMC coating on fruits, the contact angle of CS solutions with concentrations of 0.5 %, 1.0 %, and 1.5 % (w/v) decreased to 47.0°, 47.4°, and 48.5°, respectively, whereas the spreading coefficient increased to −16.0 mN/m, −17.6 mN/m and −19.8 mN/m, respectively. Subsequently, the effects of the coatings on fruit quality were investigated. The results demonstrated the promising performance of HPMC-CS two-layer coating in inhibiting fruit respiration, reducing decay rate, and maintaining nutrient content. Notably, HPMC-1.5%CS coating not only reduced the decay rate of tangerine fruit by 45 % and 31 %, in comparison to the uncoated group (CK) and pure CS coating respectively, but also maintained a high content of ascorbic acid. Therefore, this study confirmed that the use of amphiphilic polymers for improving the surface properties of fruits can effectively facilitate the wetting of hydrophilic coatings on fruits, and significantly improve the fresh-keeping performance of edible coatings.

Application of Chitosan Solution to Reduce Content Purine Substances (Total Alkaloids) in Melinjo Seeds

Application of Chitosan Solution to Reduce Content Purine Substances (Total Alkaloids) in Melinjo Seeds

Reinforced hydrogel building via formation of alginate-chitosan double network with pH & salt-responsiveness and electric conductivity for soft actuators

Aiming at green and friendly environmental protection, polyvinyl alcohol/sodium alginate/chitosan (PSCS) double network hydrogel was successfully prepared through diffusing the high molecular weight chitosan into PVA/sodium alginate (PS) hydrogel without any other toxic reagents. The polyanion hydrogels could be significantly enhanced by immersing the polyanion hydrogel in high molecular weight chitosan solution without requiring specific structure. The PSCS hydrogel had a compact and rough surface structure with the smaller porosities and larger crystallization degree compared with polyvinyl alcohol/sodium alginate hydrogels and polyvinyl alcohol/sodium alginate/Ca2+ (PSCa) hydrogels. The PSCS hydrogel possessed excellent hydrolysis resistance, the significant pH-sensitive and salt-sensitive swelling. In addition, the flexibility, Young's modulus and mechanical properties of PSCS hydrogel can be adjusted through the changing the content of sodium alginate. Moreover, PS, PSCa and PSCS had electric conductivity, and PSCS showed twice the conductivity compared to PS hydrogel. Based on differences of swelling ratio, a PSCS bilayer hydrogel was designed and showed excellent pH-driven deformation ability. The PSCS hydrogel is expected to expand the application of hydrogels in conditions involving stimulus response, and might serve as a promising intelligent actuators or soft robots.

Chitosan-TPP microcapsules for controlled drug release

Production of chitosan/sodium tripolyphosphate (CS/TPP) microcapsules via spray drying involves atomizing an emulsion containing CS, TPP, acetic acid (AcOH), and folic acid (FA) into fine droplets exposed to high-temperature, low-pressure gas flow. Solvent evaporation within the drying chamber leads to solid particle formation. Spray drying is valuable for creating solid CS/TPP microcapsules. Precise equipment parameter adjustments, like inlet temperature and gas flow rate, enable the study of microcapsule morphology, size, and properties. This adaptability allows for customization to specific pH dissolution ranges. The production method's impact on CS/TPP microcapsules was studied by modifying spray drier parameters, including inlet temperature and aspirator pressure, to enhance understanding of their behavior in solution under varied production conditions.
 In chitosan delivery systems, various approaches can encapsulate drug agents like folic acid, an analog to the cancer treatment drug methotrexate. Agents can be added to the chitosan solution pre-crosslinking, incorporated into gelation-inducing agents pre-mixing with chitosan, or included in the crosslinking mixture. Experiments were conducted to assess CS/TPP microcapsules' behavior when encapsulating agents like folic acid. Release profiles were analyzed to understand their drug delivery capabilities and potential as controlled release carriers.

Multifunctional Therapeutic Nanodiamond Hydrogels for Infected-Wound Healing and Cancer Therapy.

Wound infection and tumor recurrence are the two main threats to cancer patients after surgery. Although researchers have developed new treatment systems to address the two significant challenges simultaneously, the potential side effects of the heavy-metal-ion-based treatment systems still severely limit their widespread application in therapy. In addition, the wounds from tumor removal compared with general operative wounds are more complex. The tumor wounds mainly exhibit more hemorrhage, larger trauma area, greater vulnerability to bacterial infection, and residual tumor cells. Therefore, a multifunctional treatment platform is urgently needed to integrate rapid hemostasis, sterilization, wound healing promotion, and antitumor functions. In this work, nanodiamonds (NDs), a material that has been well proven to have excellent biocompatibility, are added into a solution of acrylic-grafted chitosan (CEC) and oxidized hyaluronic acid (OHA) to construct a multifunctional treatment platform (CEC-OHA-NDs). The hydrogels exhibit rapid hemostasis, a wound-healing-promoting effect, excellent self-healing, and injectable abilities. Moreover, CEC-OHA-NDs can effectively eliminate bacteria and inhibit tumor proliferation by the warm photothermal effect of NDs under tissue-penetrable near-infrared laser irradiation (NIR) without cytotoxicity. Consequently, we adopt a simple and convenient strategy to construct a multifunctional treatment platform using carbon-based nanomaterials with excellent biocompatibility to promote the healing of infected wounds and to inhibit tumor cell proliferation simultaneously.

FRET‐Amplified Singlet Oxygen Generation by Nanocomposites Comprising Ternary AgInS2/ZnS Quantum Dots and Molecular Photosensitizers

AbstractAntibacterial photodynamic therapy (a‐PDT) has emerged as a promising non‐invasive therapeutic modality that utilizes the combination of a photosensitive agent, molecular oxygen, and excitation light to generate reactive oxygen species (ROS), demonstrating remarkable activity against multidrug‐resistant bacterial infections. However, the effective use of conventional photosensitizers is significantly limited by a number of their shortcomings, namely, poor water solubility and low selectivity. Herein, we present a novel biocompatible water‐soluble nanocomposite based on hydrophobic tetraphenylporphyrin (TPP) molecules and hydrophilic ternary AgInS2/ZnS quantum dots incorporated into a chitosan matrix as an improved photosensitizer for a‐PDT. We demonstrated that TPP molecules could be successfully transferred into chitosan solution while remaining primarily in the form of monomers, which are capable of singlet oxygen generation. We performed a detailed analysis of the Förster resonance energy transfer (FRET) between quantum dots and TPP molecules within the nanocomposite and proposed the mechanism of the singlet oxygen efficiency enhancement via FRET.

Encapsulation and application of cell‐free extracts produced by Penicillium chrysogenum R1 in tomato plants for the control of Fusarium oxysporum

AbstractThe application of biopesticides in many industries can be hampered due to their high volatility, susceptibility to degradation when exposed to light or microbial activity, and reduced activity when exposed to stressful environmental conditions. Microencapsulation of biopesticides is a promising technique to solve and address such problems. This study aimed to encapsulate and characterize the extracts produced by Penicillium chrysogenum R1 and evaluate their antifungal activity in the plant assay. The capsules were prepared with a chitosan (0.5 mg/mL) and sodium alginate solution (2% w/v), and 20% (v/v) cell‐free extract recovered from the P. chrysogenum R1 fermentation. The capsules were synthesized in a 2.5% CaCl2 solution at room temperature. The capsules were characterized by DLS and SEM. To determine the efficiency of the free and encapsulated extract, they were applied to tomato plants infected with Fusarium oxysporum. Once the symptoms were observed, the severity and incidence of the disease, as well as the morphological parameters were evaluated. such as dry weight of aerial and root biomass, plant height, root length, stem diameter, chlorophyll content, and number of leaflets. The extract produced by P. chrysogenum R1 was encapsulated in chitosan/alginate capsules with a size range of around 300 nm. The free and encapsulated extracts allowed to efficiently control the disease caused by F. oxysporum and the development of the plants. Therefore, the extract produced by P. chrysogenum R1 encapsulated in chitosan/alginate can effectively control tomato vascular wilt caused by F. oxysporum under greenhouse conditions, promoting plant growth.

Preparation of high water-retention biodegradable kidney tray from rice straw pulp

A biomedical pulp product, a hydrogel-coated high water-retention biodegradable kidney tray from rice straw pulp, was successfully prepared in a simple and environmentally friendly process. Response surface methodology (RSM) was applied to optimize the rice straw pulping condition. The optimum condition was investigated using influential parameters and the results were 17% active alkali, 21.15% sulfidity, and 120-min pulping time, resulting in a pulp yield of 38.56% and a delignification selectivity of 25.91%. This pulping condition effectively increased the cellulose proportion and the crystallinity of the pulp, while the lignin portion was decreased. The hydrogel was prepared by mixing acid-soluble chitosan solution and rice straw pulp suspension. Introducing the hydrogel into the kidney tray led to water retention for 5 h with no leak and swelling degree up to 500%. The kidney tray also showed a good level of biodegradation, indicated by changes in surface morphology and weight loss of the sample and also high tensile strength. Therefore, this research suggests that rice straw pulp has promising application in the development of biodegradable and high-strength biomedical pulp products such as pulp-based kidney trays.

Antibiofilm Activity of Eugenol-Loaded Chitosan Coatings against Common Medical-Device-Contaminating Bacteria.

The formation of pathogenic biofilms on medical devices is a major public health concern accounting for over 65% of healthcare-associated infections and causing high infection morbidity, mortality, and a great burden to patients and the healthcare system due to its resistance to treatment. In this study, we developed a chitosan-based antimicrobial coating with embedded mesoporous silica nanoparticles (MSNs) to load and deliver eugenol, an essential oil component, to inhibit the biofilm formation of common bacteria in medical-device-related infections. The eugenol-loaded MSNs were dispersed in a chitosan solution, which was then cross-linked with glutaraldehyde and drop-casted to obtain coatings. The MSNs and coatings were characterized by dynamic light scattering, Brunauer-Emmett-Teller analysis, attenuated-total-reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, 3D optical profilometry, and scanning electron microscopy. The release behavior of eugenol-loaded MSNs and coatings and the antibiofilm and antimicrobial activity of the coatings against adherent Staphylococcus aureus, methicillin-resistant S. aureus, and Pseudomonas aeruginosa were investigated. Eugenol was released from the MSNs and coatings in aqueous conditions in a controlled manner with an initial low release, followed by a peak release, a decrease, and a plateau. While the chitosan coatings alone or with unloaded MSNs demonstrated limited antimicrobial effects and still supported biofilm formation after 24 h, the coating containing eugenol not only reduced biofilm formation but also killed the majority of the attached bacteria. It also showed biocompatibility in indirect contact with NIH/3T3 fibroblasts and a high percentage of live cells in direct contact. However, further investigations into cell proliferation in direct contact are recommended. The findings indicated that the chitosan-based coating with eugenol-loaded MSNs could be developed into an effective strategy to inhibit biofilm formation on medical devices.

Optimize the parameters for the synthesis by the ionic gelation technique, purification, and freeze-drying of chitosan-sodium tripolyphosphate nanoparticles for biomedical purposes

BackgroundPolymeric nanoparticles can be used for wound closure and therapeutic compound delivery, among other biomedical applications. Although there are several nanoparticle obtention methods, it is crucial to know the adequate parameters to achieve better results. Therefore, the objective of this study was to optimize the parameters for the synthesis, purification, and freeze-drying of chitosan nanoparticles. We evaluated the conditions of agitation speed, anion addition time, solution pH, and chitosan and sodium tripolyphosphate concentration.ResultsChitosan nanoparticles presented an average particle size of 172.8 ± 3.937 nm, PDI of 0.166 ± 0.008, and zeta potential of 25.00 ± 0.79 mV, at the concentration of 0.1% sodium tripolyphosphate and chitosan (pH 5.5), with a dripping time of 2 min at 500 rpm. The most representative factor during nanoparticle fabrication was the pH of the chitosan solution, generating significant changes in particle size and polydispersity index. The observed behavior is attributed to the possible excess of sodium tripolyphosphate during synthesis. We added the surfactants poloxamer 188 and polysorbate 80 to evaluate the stability improvement during purification (centrifugation or dialysis). These surfactants decreased coalescence between nanoparticles, especially during purification. The centrifugation increased the zeta potential to 40.8–56.2 mV values, while the dialyzed samples led to smaller particle sizes (152–184 nm). Finally, freeze-drying of the chitosan nanoparticles proceeded using two cryoprotectants, trehalose and sucrose. Both adequately protected the system during the process, and the sugar concentration depended on the purification process.ConclusionsIn Conclusion, we must consider each surfactant's benefits in formulations for selecting the most suitable. Also, it is necessary to do more studies with the molecule to load. At the same time, the use of sucrose and trehalose generates adequate protection against the freeze-drying process, even at a 5% w/v concentration. However, adjusting the percentage concentration by weight must be made to work with the CS-TPP NPs purified by dialysis.

Anticancer Activity of Astaxanthin-Incorporated Chitosan Nanoparticles.

Astaxanthin (AST)-encapsulated nanoparticles were fabricated using glycol chitosan (Chito) through electrostatic interaction (abbreviated as ChitoAST) to solve the aqueous solubility of astaxanthin and improve its biological activity. AST was dissolved in organic solvents and then mixed with chitosan solution, followed by a dialysis procedure. All formulations of ChitoAST nanoparticles showed small diameters (less than 400 nm) with monomodal distributions. Analysis with Fourier transform infrared (FT-IR) spectroscopy confirmed the specific peaks of AST and Chito. Furthermore, ChitoAST nanoparticles were formed through electrostatic interactions between Chito and AST. In addition, ChitoAST nanoparticles showed superior antioxidant activity, as good as AST itself; the half maximal radical scavenging concentrations (RC50) of AST and ChitoAST nanoparticles were 11.8 and 29.3 µg/mL, respectively. In vitro, AST and ChitoAST nanoparticles at 10 and 20 µg/mL properly inhibited the production of intracellular reactive oxygen species (ROSs), nitric oxide (NO), and inducible nitric oxide synthase (iNOS). ChitoAST nanoparticles had no significant cytotoxicity against RAW264.7 cells or B16F10 melanoma cells, whereas AST and ChitoAST nanoparticles inhibited the growth of cancer cells. Furthermore, AST itself and ChitoAST nanoparticles (20 µg/mL) efficiently inhibited the migration of cancer cells in a wound healing assay. An in vivo study using mice and a pulmonary metastasis model showed that ChitoAST nanoparticles were efficiently delivered to a lung with B16F10 cell metastasis; i.e., fluorescence intensity in the lung was significantly higher than in other organs. We suggest that ChitoAST nanoparticles are promising candidates for antioxidative and anticancer therapies of B16F10 cells.

Engineering of a decellularized bovine skin coated with antibiotics-loaded electrospun fibers with synergistic antibacterial activity for the treatment of infectious wounds.

An ideal antibacterial wound dressing with strong antibacterial behavior versus highly drug-resistant bacteria and great wound-healing capacity is still being developed. There is a clinical requirement to progress the current clinical cares that fail to fully restore the skin structure due to post-wound infections. Here, we aim to introduce a novel two-layer wound dressing using decellularized bovine skin (DBS) tissue and antibacterial nanofibers to design a bioactive scaffold with bio-mimicking the native extracellular matrix of both dermis and epidermis. For this purpose, polyvinyl alcohol (PVA)/chitosan (CS) solution was loaded with antibiotics (colistin and meropenem) and electrospun on the surface of the DBS scaffold to fabricate a two-layer antibacterial wound dressing (DBS-PVA/CS/Abs). In detail, the characterization of the fabricated scaffold was conducted using biomechanical, biological, and antibacterial assays. Based on the results, the fabricated scaffold revealed a homogenous three-dimensional microstructure with a connected pore network, a high porosity and swelling ratio, and favorable mechanical properties. In addition, according to the cell culture result, our fabricated two-layer scaffold surface had a good interaction with fibroblast cells and provided an excellent substrate for cell proliferation and attachment. The antibacterial assay revealed a strong antibacterial activity of DBS-PVA/CS/Abs against both standard strain and multidrug-resistant clinical isolates of Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli. Our bilayer antibacterial wound dressing is strongly suggested as an admirable wound dressing for the management of infectious skin injuries and now promises to advance with preclinical and clinical research.

Application of Pistacia atlantica Pickering emulsion-filled chitosan gel for targeted delivery of curcumin.

Emulsion-filled hydrogels are a growing system in the food industry for delivering bioactive compounds. In this study, Baneh gum (BG) particles were prepared as a Pickering emulsion stabilizer for curcumin delivery. Then, BG Pickering emulsion was added to the chitosan solution (1.5%, 2.0%, and 2.5% w/w) in different Pickering emulsion (PE):hydrogel (HYD) ratios (1:3, 1:5, and 1:7) to create an emulsion-filled gel. The highest amount of Cur stability after the 3rd week of storage was observed in the sample containing 2.0% CS and a 1:7 PE:HYD ratio (97.36%). Pickering emulsion and emulsion-filled gel significantly protected the antioxidant activity of curcumin against the thermal process (p < .05). Curcumin loading in the emulsion-filled gel provided better protection against the gastric condition compared to the emulsion system. The chitosan hydrogel swells in an acidic environment, but its combination with the anionic structure of the emulsion causes a lower release of curcumin in the stomach environment, which can help the stability of curcumin in the digestive system and have a controlled release in the gastrointestinal tract.

Dual-signal viscosity flow paper sensor for ATP detection based on bio-recognition and nanozyme activity regulation of ZIF-90

Adenosine triphosphate (ATP) is an important biological biomarker, but its rapid extracellular decomposition poses challenges for on-site detection. We report a paper-based dual-readout viscosity flow sensor enabling rapid, equipment-free quantification of ATP. The assay integrates molybdenum disulfide nanozymes for signal amplification with zeolitic imidazolate framework-90 (ZIF-90) for selective ATP recognition and nanozyme regulation. In the presence of ATP, the intact chitosanase-encapsulated ZIF-90 structure was disintegrated to release chitosanase and thus hydrolyzed chitosan hydrogel, decreasing the viscosity of chitosan solution. Moreover, elimination of ZIF-90 inhibitory effect reactivated the catalytic activity of MoS2 nanozyme, resulting in the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to produce obvious color change. The analytical signals, combining the distance- and colorimetric- readout, were directly displayed on filter paper without further processed. The proposed dual-readout viscosity flow sensor exhibited remarkable sensitivity for ATP detection with detection limits down to 0.038 nM with the distance-readout and 0.057 nM for the colorimetric-readout. Furthermore, we developed an integrated paper kit with a printed scale and color card for standardized on-site analysis without instrumentation. Successful application for ATP quantification in bacterial biofilms and blood samples demonstrates the sensor’s strong performance and potential for decentralized testing.

Investigating the anti-inflammatory and bone repair-promoting effects of an injectable porous hydrogel containing magnesium ions in a rat periodontitis mode

Periodontitis is associated with several systemic diseases, and advanced periodontitis is often linked to an extensive inflammatory microenvironment and irregularly shaped alveolar bone defects. However, eliminating periodontal inflammation in a minimally invasive manner while repairing irregularly shaped bone defects is clinically challenging. In comparison to traditional bone grafts, a thermo-sensitive hydrogel can be injected into deep periodontal pockets, forming and filling the alveolar bone defects in situ. In this study, porous injectable thermo-sensitive hydrogels containing magnesium ions were prepared by adding magnesium particles (MPs) to a glycerophosphate solution and combining this mixture with a chitosan solution. The incorporation of MPs created interconnected pores in the hydrogel, exhibiting high cytocompatibility and maintaining cell viability, proliferation, spreading, and osteogenesis in vitro. Evaluation on an experimental periodontitis rat model, using micro-computed tomography and histological analyses, demonstrated that this Mg2+-containing hydrogel effectively reduced periodontal inflammation, inhibited osteoclast activity, and partially repaired inflammation-induced alveolar bone loss. These results suggest that Mg2+-containing thermo-sensitive porous hydrogels might be promising candidates for treating periodontitis.

A chitosan-coated PCL/nano-hydroxyapatite aerogel integrated with a nanofiber membrane for providing antibacterial activity and guiding bone regeneration.

A guided bone regeneration (GBR) membrane can act as a barrier to prevent the invasion and interference from foreign soft tissues, promoting infiltration and proliferation of osteoblasts in the bone defect area. Herein, a composite scaffold with dual functions of osteogenesis and antibacterial effects was prepared for GBR. A polycaprolactone (PCL)/nano-hydroxyapatite (n-HA) aerogel produced by electrospinning and freeze-drying techniques was fabricated as the loose layer of the scaffold, while a PCL nanofiber membrane was used as the dense layer. Chitosan (CS) solution served as a middle layer to provide mechanical support and antibacterial effects between the two layers. Morphological results showed that the loose layer had a porous structure with n-HA successfully dispersed in the aerogels, while the dense layer possessed a sufficiently dense structure. In vitro antibacterial experiments illustrated that the CS solution in the middle layer stabilized the scaffold structure and endowed the scaffold with good antibacterial properties. The cytocompatibility results indicated that both fibroblasts and osteoblasts exhibited superior cell activity on the dense and loose layers, respectively. In particular, the dense layer made of nanofibers could work as a barrier layer to inhibit the infiltration of fibroblasts into the loose layer. In vitro osteogenesis analysis suggested that the PCL/n-HA aerogel could enhance the bone induction ability of bone mesenchymal stem cells, which was confirmed by the increased expression of the alkaline phosphatase activity. The loose structure facilitated the infiltration and migration of bone mesenchymal stem cells for better osteogenesis. In summary, such a composite scaffold exhibited excellent osteogenic and antibacterial properties as well as the barrier effect, thus holding promising potential for use as GBR materials.

The Use of Natural Polymers to Enhance Oil Recovery

This paper reports a laboratory study on the use of natural polymers to increase oil recovery. The use of natural polymers compared to synthetic polymers is more economical due to their abundant availability, renewability, biodegradability, and non-toxicity to the environment as they do not use chemicals. The purpose of this research is to measure the aqueous solution stability test and recovery factor produced by natural polymers through core flooding tests. The natural polymers used are Shrimp Chitosan, Crab Chitosan, Cyclea Barbata Miers, Mesona Palustris, and Seaweed. The methods used in this research are aqueous solution stability test and core flooding test. The shrimp chitosan solution used had a concentration from 5,000; 10,000 and 15,000 ppm and 2 salinities between 10,000 and 20,000 ppm. The crab chitosan solution used had a concentration from 5,000; 10,000 and 15,000 ppm with 2 salinities between 10,000 and 20,000 ppm. The Cyclea barbata Miers solution used had a concentration from 1,500; 2,500 and 3,500 ppm and 2 salinities between 7,000 and 15,000 ppm. The Mesona Palustris solution used had a concentration from 500; 1,000 and 2,000 ppm and 3 salinities from 10,000; 15,000 and 20,000 ppm. The Seaweed solution used had a concentration from 1,000; 2,000 and 3,000 ppm and 3 salinities from 5,000; 10,000 and 15,000 ppm. Sandpack is used as a porous media for crab chitosan experiments, while sandstone core is used for Cyclea Barbata Miers and Mesona Palustris with crude oil 44°API. The aqueous solution stability test showed that all polymer solution samples were clear for various concentrations and salinities. Except for the solutions of Cyclea barbata Miers and Masona palustris which are greenish and blackish respectively. Transmittance for shrimp and crab chitosan solutions shows a value of more than 80%. This shows that natural polymers are compatible with brine. Flooding tests were carried out to measure oil recovery related to the use of natural polymers. The experimental results showed that the best additional oil recovery was 10.3% using crab chitosan solution injection. The chitosan solution used had a concentration of 15,000 ppm and a viscosity of 1,729 cp. We can conclude that the addition of polymer can improve recovery factor.