Novel sustained-release implant of herb extract using chitosan

Pharmaceutical applications of chitosan in skin regeneration: A review

Skin regeneration is the process that restores damaged tissues. When the body experiences trauma or surgical incisions, the skin and tissues on the wound surface become damaged. The body repairs this damage through complex physiological processes to restore the original structural and functional states of the affected tissues. Chitosan, a degradable natural bioactive polysaccharide, has attracted widespread attention partly owing to its excellent biocompatibility and antimicrobial properties; additionally, a modified form of this compound has been shown to promote skin regeneration. This review evaluates the recent research progress in the application of chitosan to promote skin regeneration. First, we discuss the basic principles of the extraction and preparation processes of chitosan from its source. Subsequently, we describe the functional properties of chitosan and the optimization of these properties through modification. We then focus on the existing chitosan-based biomaterials developed for clinical applications and their corresponding effects on skin regeneration, particularly in cases of diabetic and burn wounds. Finally, we explore the challenges and prospects associated with the use of chitosan in skin regeneration. Overall, this review provides a reference for related research and contributes to the further development of chitosan-based products in cutaneous skin regeneration.

Synthesis of β-acids loaded chitosan-sodium tripolyphosphate nanoparticle towards controlled release, antibacterial and anticancer activity

The development of nanoparticles loaded with natural active ingredients is one of the hot trends in the pharmaceutical industry. Herein, chitosan was selected as the base material, and sodium tripolyphosphate was chosen as the cross-linking agent. Chitosan nanoparticles loaded with β-acids from hops were prepared by the ionic cross-linking method. The results of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that chitosan nanoparticles successfully encapsulated β-acids. The loading capacity of chitosan nanoparticles with β-acids was 2.00 %-18.26 %, and the encapsulation efficiency was 0.58 %-55.94 %. Scanning electron microscopy (SEM), transmission electron microscope (TEM), particle size, and zeta potential results displayed that the nanoparticles revealed a sphere-like distribution with a particle size range of 241-261 nm, and the potential exhibited positive potential (+14.47-+16.27 mV). The chitosan nanoparticles could slowly release β-acids from different simulated release media. Notably, the β-acids-loaded nanoparticles significantly inhibited Staphylococcus aureus ATCC25923 (S. aureus) and Escherichia coli ATCC25922 (E. coli). Besides, β-acids-loaded chitosan nanoparticles were cytotoxic to colorectal cancer cells (HT-29 and HCT-116). Therefore, applying chitosan nanoparticles can further expand the application of β-acids in biomedical fields.

Preparation, characterization, and in vitro-in silico biological activities of Jatropha pelargoniifolia extract loaded chitosan nanoparticles

Jatropha pelargoniifolia (JP) is a medicinal plant that is widely used in traditional medicine owing to its broad range of therapeutic activities. Despite its promising pharmacological activities, the use of plant extracts has several limitations which can be overcome using pharmaceutical nanotechnology. The aim of this study was to systematically investigate the effect of nanoencapsulation on the antimicrobial and anticancer activities of JP extract. JP-loaded chitosan nanoparticles (JP-CSNPs) were prepared using the ionic gelation method and characterized in terms of size, polydispersity index, zeta potential, encapsulation efficiency, and release profile. Transmission electron microscopy was used to observe the morphology of the nanoparticles. The mean particle size, zeta potential, and encapsulation efficiency of optimized JP-CSNPs were 185.5 nm, 44 mV, and 78.5%, respectively. The release profile of the JP-CSNPs was mainly dependent on the pH of the surrounding medium, and the JP extract was released in a controlled manner over time. The total phenolic and flavonoid contents in JP extract were 191.8 mg GAE/g extract and 51.4 mg of QE/g extract, respectively. The results of a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay showed that JP-CSNPs retained the antioxidant activity of unencapsulated JP extract. JP-CSNPs also exhibited higher antimicrobial activity against gram-positive bacteria than against gram-negative bacteria, and their minimum inhibitory concentration was 1.6-fold lower than that of blank nanoparticles, indicating the synergy between JP extract and nanoparticles. In vitro cytotoxicity studies using A549 human lung adenocarcinoma cells revealed that JP-CSNPs had a 2-fold lower half-maximal inhibitory concentration than free extract. Molecular docking analyses revealed that the active phytoconstituent of JP extract, linarin, binds strongly to the active sites of bacterial DNA gyrase B and human DNA topoisomerase IIα and thus, may inhibit their activities. Computational analysis results supported the in vitro finding that JP-CSNPs act as an anticancer and antimicrobial agent. Taken together, the results of this study highlighted the advantages of using CSNPs as a nanocarrier for herbal extracts, thus providing a potential strategy for improving plant-based therapeutics.

Traditional Chinese Medicine and orthopedic biomaterials: Host of opportunities from herbal extracts

The role of Traditional Chinese Medicine (TCM), especially herbs or herbal extracts, in treating diseases has received increasing attention. This review focuses on the use of herbal extracts as signaling molecules and functional materials in the field of orthopedics, biomaterial science and bone tissue engineering strategies. A literature review using both Chinese and English references on herbs and herbal extracts based on TCM theory used in orthopedics and biomaterial science was performed. We discuss the efficacy of herbs, the active extracts from these herbs, the combination of herbal extracts and biomaterials and, finally, the application of herbal extracts to the biomaterials specific to orthopedics. Only a few studies have confirmed the feasibility of applying herbal extracts to biomaterials to improve the role of biomaterials and/or optimize drug delivery and release in orthopedics. In this context, this review reveals a new and promising direction for herbal extracts, where the use of herbal extracts based on TCM systemic treatment, can change the limited modern medicine view of biomaterials as "only for local treatment" when considering its efficacy.

Co-regulative effects of chitosan-fennel seed extract system on the hormonal and biochemical factors involved in the polycystic ovarian syndrome

There is a renewed interest in the application of chitosan-based drug delivery systems over the last few years. In this study, the ionic gelation method was used to prepare chitosan-engaged tripolyphosphate ions, as the cross-linking molecule, (Chit-TPP) and concurrent loading of the biomolecules of the ethanolic extract of fennel, Foeniculum vulgare, seed (FEC@NBC). The samples were characterized by SEM, DLS, TGA, FTIR, XRD, GC-MS, and zeta potential, and their effects on the related hormonal and biochemical factors of the rats with polycystic ovarian syndrome (PCOS) were assessed. The estradiol valerate-induced PCOS in female rats was confirmed by vaginal smear test and subsequent histological screening. The PCOS-induced rats were treated by fennel seed extract (FSX), Chit-TPP, and FEC@NBC. The process of treatment was monitored by measuring the serum levels of testosterone, luteinizing hormone, follicle-stimulating hormone, insulin, glucose, high-density lipoprotein cholesterol, total cholesterol, and total triglyceride after 16 days of treatment and compared with healthy control and untreated PCOS-control groups. The FEC@NBC administration contributed to the remarkable hormonal, glucose, and lipid profile regulation in the rats with PCOS. The significance of FEC@NBC performance in dealing with PCOS complications compared to that of the only extract could be resulted from the effective targeted delivery and stability of phytomolecules when encapsulated in Chit-TPP.

Enhanced oral bioavailability of Tanshinone IIA using lipid nanocapsules: Formulation, in-vitro appraisal and pharmacokinetics

Tanshinone IIA (TSIIA) is a promising phytomedicine that has been extensively studied due to its numerous biological activities, especially as an anticancer drug. However, it suffers from poor oral bioavailability owing to low aqueous solubility, poor permeability and exposure to first-pass metabolism. This study endeavored to improve TSIIA oral bioavailability by encapsulation into lipid nanocapsules (LNCs) for the first time. A previously reported phase-inversion method was used to prepare Tanshinone II A loaded LNCs (TSIIA-LNCs) with slight modifications based on a constructed phase diagram. They were then in-vitro characterized and their oral pharmacokinetics were studied in rats. TSIIA-LNCs showed excellent colloidal properties (size; 70 nm, PDI < 0.2 and zeta-potential; -13.5 mV), a high percent entrapment efficiency (98%) and a good drug payload (2.6 mg/g). Furthermore, the in-vivo pharmacokinetic study revealed a significant enhancement in both the rate and extent of absorption of TSIIA-LNCs compared with TSIIA suspension with about 3.6-fold increase in AUC _0-inf value (p ≤ 0.01). Additionally, a significant increase in both half-life and mean residence time was exhibited by TSIIA-LNCs (p ≤ 0.01), confirming their long circulating properties. Therefore, the elaborated LNCs could be addressed as a promising nanoplatform permitting higher TSIIA oral bioavailability.

Strategy to design a smart photocleavable and pH sensitive chitosan based hydrogel through a novel crosslinker: a potential vehicle for controlled drug delivery

We report herein the synthesis of a novel photocleavable crosslinker, 4-formylphenyl 4-((4-formylphenoxy)methyl)-3-nitrobenzoate (CHO-ONB-CHO) and its joining with amine-based polysaccharides, viz. chitosan, resulting in the formation of a dual stimuli-responsive (ONB-chitosan) hydrogel having UV- and pH-responsive sites. The detailed mechanism for the formation of CHO-ONB-CHO and ONB-chitosan hydrogel is proposed. The (CHO-ONB-CHO) crosslinker was characterized using 1H-NMR, LCMS and UV-visible spectroscopy. The dual responsive hydrogel is characterized by FTIR, SEM, XRD, DSC and TGA. The crosslinked hydrogel displayed mechanical robustness with a storage modulus of about 1741 pa. The pH-responsiveness of the hydrogel was studied via equilibrium swelling studies in various pH media at 37 °C. The photocleavable behavior of the crosslinker was observed in the UV-absorption range of 310-340 nm and the hydrogel exhibited maximum swelling at pH 5.7. The higher swelling of the hydrogel in acidic conditions and its photo-responsiveness can be exploited for the controlled, temporal and spatial release of therapeutic drugs at any inflammatory areas with acidic environments. It was observed that the hydrogel exhibited higher drug release at pH 5.7 than at pH 7.4.

Chitin and chitosan: biopolymers for wound management

Chitin and chitosan are biopolymers with excellent bioactive properties, such as biodegradability, non-toxicity, biocompatibility, haemostatic activity and antimicrobial activity. A wide variety of biomedical applications for chitin and chitin derivatives have been reported, including wound-healing applications. They are reported to promote rapid dermal regeneration and accelerate wound healing. A number of dressing materials based on chitin and chitosan have been developed for the treatment of wounds. Chitin and chitosan with beneficial intrinsic properties and high potential for wound healing are attractive biopolymers for wound management. This review presents an overview of properties, biomedical applications and the role of these biopolymers in wound care.

Incorporated α-amylase and starch in an edible chitosan–procyanidin complex film increased the release amount of procyanidins

The α-amylase was embedded in edible chitosan–procyanidins film, and the release of procyanidins was by starch hydrolysis.

A Biomimetic Material with a High Bio-responsibility for Bone Reconstruction and Tissue Engineering

A biomimetic composite was prepared using type-I collagen as the matrix, and particles of sol-gel-derived bioactive glass (58S), hyaluronic acid and phosphatidylserine as additives. The material has an interconnected 3-D porous structure with a porosity > 85%. When incubated in simulated body fluid (SBF), the composite induced the formation of microcrystals of bone-like hydroxyapatite (HA), suggesting good bioactive properties. During the in vitro cell-culture experiment, MC3T3-E1 cells adhered to, migrated and spread on the surface of the porous composite. The material was employed to repair a 10-mm defect in a rabbit's radius. The composite was gradually degraded within 8 weeks and replaced by new bone. After 12 weeks, the bone marrow cavity was restored and the Haversian canal was noted from the histological observation. The biomimetic composite is a potential scaffold material for bone reconstruction and bone tissue engineering.

Methods of Monitoring Cell Fate and Tissue Growth in Three-Dimensional Scaffold-Based Strategies for In Vitro Tissue Engineering

In the field of tissue engineering, there is a need for methods that allow assessing the performance of tissue-engineered constructs noninvasively in vitro and in vivo. To date, histological analysis is the golden standard to retrieve information on tissue growth, cellular distribution, and cell fate on tissue-engineered constructs after in vitro cell culture or on explanted specimens after in vivo applications. Yet, many advances have been made to optimize imaging techniques for monitoring tissue-engineered constructs with a sub-mm or μm resolution. Many imaging modalities have first been developed for clinical applications, in which a high penetration depth has been often more important than lateral resolution. In this study, we have reviewed the current state of the art in several imaging approaches that have shown to be promising in monitoring cell fate and tissue growth upon in vitro culture. Depending on the aimed tissue type and scaffold properties, some imaging methods are more applicable than others. Optical methods are mostly suited for transparent materials such as hydrogels, whereas magnetic resonance-based methods are mostly applied to obtain contrast between hard and soft tissues regardless of their transparency. Overall, this review shows that the field of imaging in scaffold-based tissue engineering is developing at a fast pace and has the potential to overcome the limitations of destructive endpoint analysis.

Selection of animal models for pre-clinical strategies in evaluating the fracture healing, bone graft substitutes and bone tissue regeneration and engineering

In vitro assays can be useful in determining biological mechanism and optimizing scaffold parameters, however translation of the in vitro results to clinics is generally hard. Animal experimentation is a better approximation than in vitro tests, and usage of animal models is often essential in extrapolating the experimental results and translating the information in a human clinical setting. In addition, usage of animal models to study fracture healing is useful to answer questions related to the most effective method to treat humans. There are several factors that should be considered when selecting an animal model. These include availability of the animal, cost, ease of handling and care, size of the animal, acceptability to society, resistance to surgery, infection and disease, biological properties analogous to humans, bone structure and composition, as well as bone modeling and remodeling characteristics. Animal experiments on bone healing have been conducted on small and large animals, including mice, rats, rabbits, dogs, pigs, goats and sheep. This review also describes the molecular events during various steps of fracture healing and explains different means of fracture healing evaluation including biomechanical, histopathological and radiological assessments.

Magnesium-containing nanostructured hybrid scaffolds for enhanced dentin regeneration

Dental caries is one of the most prevalent chronic diseases in the United States, affecting 92% of adults aged 20-64 years. Scaffold-based tissue engineering represents a promising strategy to replace damaged dental structures and restore their biological functions. Current single-component scaffolding materials used for dental tissue regeneration, however, cannot provide the proper microenvironment for dental stem/progenitor cell adhesion, proliferation, and differentiation; new biomimetic hybrid scaffolds are needed to promote better dental tissue formation. In this work, we developed a biomimetic approach to prepare three-dimensional (3D) nanofibrous gelatin/magnesium phosphate (NF-gelatin/MgP) hybrid scaffolds. These scaffolds not only mimic the nanostructured architecture and the chemical composition of natural dentin matrices but also constantly present favorable chemical signals (Mg ions) to dental pulp stem cells (DPSCs), thus providing a desirable microenvironment to facilitate DPSC proliferation, differentiation, and biomineralization. Synthesized hybrid NF-gelatin/MgP possesses natural extracellular matrix (ECM)-like architecture, high porosity, high pore interconnectivity, well-defined pore size, and controlled Mg ion release from the scaffold. Adding MgP into NF-gelatin also increased the mechanical strength of the hybrid scaffold. The sustained release of Mg ions from the NF-gelatin/MgP (MgP=10% wt/wt) scaffold significantly enhanced the proliferation, differentiation, and biomineralization of human DPSCs in vitro. The alkaline phosphatase (ALP) activity and the gene expressions for odontogenic differentiation (collagen I [Col I], ALP, osteocalcin [OCN], dentin sialophosphoprotein [DSPP], and dentin matrix protein 1 [DMP1]) were all significantly higher (p<0.05) in the NF-gelatin/MgP group than in the NF-gelatin group. Those results were further confirmed by hematoxylin and eosin (H&E) and von Kossa staining, as shown by greater ECM secretion and mineral deposition in the hybrid scaffold. Consistent with the in vitro study, the DPSCs/NF-gelatin/MgP constructs produced greater ECM deposition, hard tissue formation, and expression of marker proteins (DSPP, DMP1, Col I) for odontogenic differentiation than did the DPSCs/NF-gelatin after 5 weeks of ectopic implantation in rude mice. The controlled release of metallic ions from biomimetic nanostructured hybrid scaffolds, therefore, is a promising approach to enhancing the biological capability of the scaffolds for dental tissue regeneration.

Three-dimensional scaffolds for tissue engineering applications: role of porosity and pore size

Tissue engineering applications commonly encompass the use of three-dimensional (3D) scaffolds to provide a suitable microenvironment for the incorporation of cells or growth factors to regenerate damaged tissues or organs. These scaffolds serve to mimic the actual in vivo microenvironment where cells interact and behave according to the mechanical cues obtained from the surrounding 3D environment. Hence, the material properties of the scaffolds are vital in determining cellular response and fate. These 3D scaffolds are generally highly porous with interconnected pore networks to facilitate nutrient and oxygen diffusion and waste removal. This review focuses on the various fabrication techniques (e.g., conventional and rapid prototyping methods) that have been employed to fabricate 3D scaffolds of different pore sizes and porosity. The different pore size and porosity measurement methods will also be discussed. Scaffolds with graded porosity have also been studied for their ability to better represent the actual in vivo situation where cells are exposed to layers of different tissues with varying properties. In addition, the ability of pore size and porosity of scaffolds to direct cellular responses and alter the mechanical properties of scaffolds will be reviewed, followed by a look at nature's own scaffold, the extracellular matrix. Overall, the limitations of current scaffold fabrication approaches for tissue engineering applications and some novel and promising alternatives will be highlighted.

Importance of novel drug delivery systems in herbal medicines

Novel drug delivery system is a novel approach to drug delivery that addresses the limitations of the traditional drug delivery systems. Our country has a vast knowledge base of Ayurveda whose potential is only being realized in the recent years. However, the drug delivery system used for administering the herbal medicine to the patient is traditional and out-of-date, resulting in reduced efficacy of the drug. If the novel drug delivery technology is applied in herbal medicine, it may help in increasing the efficacy and reducing the side effects of various herbal compounds and herbs. This is the basic idea behind incorporating novel method of drug delivery in herbal medicines. Thus it is important to integrate novel drug delivery system and Indian Ayurvedic medicines to combat more serious diseases. For a long time herbal medicines were not considered for development as novel formulations owing to lack of scientific justification and processing difficulties, such as standardization, extraction and identification of individual drug components in complex polyherbal systems. However, modern phytopharmaceutical research can solve the scientific needs (such as determination of pharmacokinetics, mechanism of action, site of action, accurate dose required etc.) of herbal medicines to be incorporated in novel drug delivery system, such as nanoparticles, microemulsions, matrix systems, solid dispersions, liposomes, solid lipid nanoparticles and so on. This article summarizes various drug delivery technologies, which can be used for herbal actives together with some examples.

Factors of osteogenesis influencing various human stem cells on third-generation gelatin/β-tricalcium phosphate scaffold material

Human bone marrow-derived stem cells (hBMSCs) and adipose-derived stem cells (hASCs) have been used to regenerate bone. Both sources are claimed to have comparable osteogenic potential, but few comparative studies are available. Third-generation biomaterials have been developed to reduce steps in regenerating tissues. For osteogenesis gelatin/β-tricalcium phosphate (β-TCP) scaffolds with incorporated controlled-release bone morphogenetic protein-2 (BMP-2) as third-generation biomaterials were recently developed. So far, few studies on protein-induced osteogenesis versus chemical-induced osteogenesis have been performed. This study evaluates the osteogenic potential of hBMSCs versus hASCs derived on gelatin/β-TCP scaffolds in vitro under four different conditions. Gelatin/β-TCP scaffolds with and without incorporated controlled-release BMP-2 were seeded with hBMSCs or hASCs under oscillating fluid conditions in osteogenic (OS) medium or growth medium (GM). All were evaluated radiologically (computed tomography [CT] scan), histologically, biomechanically, and for gene expression at 1, 2, 4, and 6 weeks. The highest radiological densities were seen in specimens at 6 weeks with controlled-release BMP-2, close to native bone. HBMSCs, hASCs, OS, and GM conditions resulted in similar bone formation with gelatin/β-TCP scaffolds and incorporated controlled-release BMP-2. This was confirmed histologically by Toluidine Blue and van Kossa staining and biomechanically. Gene expression studies of these specimens showed the presence of preosteoblasts, transitory osteoblasts, and secretory osteoblasts. Specimens comprised of gelatin/β-TCP scaffolds without incorporated controlled release BMP-2 in OS medium showed lesser bone formation. hASCs and hBMSCs have similar osteogenic potential. hASCs are an attractive alternative to hBMSCs for bone regeneration using third-generation gelatin/β-TCP scaffolds with incorporated controlled-release BMP-2.

Antibiotic-loaded chitosan film for infection prevention: A preliminary in vitro characterization

The growing infection rate by methicillin-resistant Staphylococcus aureus, especially with bone fracture fixation implants, is a major concern in extremity musculoskeletal wound treatment. This preliminary investigation evaluates the ability of chitosan film to be loaded with daptomycin and vancomycin in the operating room, in situ loading, and applied to musculoskeletal fixation devices to lessen or prevent infection. Films with 61, 71, and 80% degrees of deacetylation (DDA) made using lactic or acetic acid solvents were analyzed for their antibiotic uptake, elution, and activity along with film swelling ratio, ultimate tensile strength, Young's modulus, adhesive strength, and degradation. Chitosan films after 1 min of rehydration were able in a simulated, clinical setting to maintain mechanical integrity and adhesive strength to be applied to bone fracture fixation devices or implant surfaces. The film percent degradation increased with DDA increasing from 61 to 80%, but film degradation rate decreased in the presence of antibiotics. Eighty percent DDA chitosan films were optimal for absorbing and eluting antibiotics. Antibiotics eluted by the films were active against Staphylococcus aureus. These findings indicate that an 80% DDA chitosan film is potentially advantageous as a clinically adjunctive treatment in musculoskeletal injuries to lessen or prevent infections.

Macroporous hydrogel scaffolds and their characterization by optical coherence tomography

A simple porogen-leaching method to fabricate macroporous cyclic acetal hydrogel cell scaffolds is presented. Optical coherence tomography (OCT) was applied for nondestructive imaging and quantitative characterization of the scaffold structures. High-resolution OCT reveals the microstructures of the engineered tissue scaffolds in three dimensions. It also enables subsequent image processing to investigate quantitatively several key morphological design parameters for macroporous scaffolds, including the volume porosity, pore interconnectivity, and pore size. Two image-processing algorithms were adapted: three-dimensional labeling was applied to assess the interconnectivity, and erosion was applied to assess the pore size. Scaffolds with different design parameters were imaged, characterized, and compared. OCT imaging and image processing successfully discriminated scaffolds made from different formulations in terms of volume porosity, interconnectivity, and pore size. The cell viability and their spread across the scaffolds were confirmed by the fluorescence microscopy co-registered with OCT.

Chitosan hydrogel containing GMCSF and a cancer drug exerts synergistic anti-tumor effects via the induction of CD8+ T cell-mediated anti-tumor immunity

Cancer treatments consisting of a combination of chemotherapy and immunotherapy have been vigorously exploited to further improve the efficacy of cancer therapies. In this study, we utilized a chitosan hydrogel (CH) system loaded with GMCSF and a cancer drug as a chemo-immunotherapeutic agent in an effort to assess the effects on tumor growth in mice using TC-1 cervical tumor cells, which express the tumor-specific antigen, HPV-16 E7. The growth of TC-1 tumors was significantly reduced in mice treated with a CH harboring a cancer drug (doxorubicin (DOX), cisplatin (CDDP), or cyclophosphamide (CTX)) and GMCSF (CH-a cancer drug + GMCSF), as compared to other groups that were treated with CH containing only a cancer drug(CH-a cancer drug) or GMCSF(CH-GMCSF). Among the cancer drugs, CTX exerted the most potent anti-tumor effects. Interestingly, the intra-tumoral injection of CH-a cancer drug + GMCSF induced a significant E7-specific CD8(+) T cell immune response as compared to CH-GMCSF or CH-a cancer drug. This enhancement of tumor antigen-specific CD8(+) T cell immunity was associated principally with the anti-tumor effects induced by CH-CTX + GMCSF, as demonstrated by antibody depletion. Collectively, the aforementioned results indicate that co-treatment of tumors with a combination of GMCSF and a cancer drug incorporated into a CH system results in synergistic anti-tumor effects, which occur via the induction of a tumor antigen-specific CD8(+) T cell-mediated anti-tumor immunity. This study demonstrates the use of a biodegradable hydrogel system for the co-delivery of an immunoadjuvant and an anti-cancer drug for successful chemo-immunotherapy.

Chitosan microspheres containing the natural urucum pigment

An increasing trend in the food and pharmaceutical industries is toward replacing synthetic additives with natural products. However, in this regard, difficulties may be encountered due to the instability of such compounds. Encapsulation has become an important process to protect natural pigments. This paper reports on the encapsulation of the natural urucum pigment with chitosan using different techniques and its release under different pH conditions. The material loaded with pigment was evaluated by infrared spectroscopy, scanning electron microscopy and thermal analysis. Chitosan was found to be an effective encapsulating agent for urucum pigment. No investigations have previously been reported on the relation of chitosan to the stability of encapsulated natural pigments.

Releasing growth factors from activated human platelets after chitosan stimulation: a possible bio-material for platelet-rich plasma preparation

INTRODUCTION

Thrombin is commonly used for activating the platelets and releasing the growth factors on the application of platelet-rich plasma (PRP). We have previously reported that chitosan can enhance rabbit platelet aggregation. In this study, the effects of chitosan on the subsequent growth factors release after human platelets activation were examined to evaluate the possibility of chitosan being used as a substitute for thrombin during PRP preparation.

MATERIAL AND METHODS

Human platelet activation was determined by aggregation, adhesion and alpha-granule membrane glycoprotein expression. Platelet aggregation was measured by the turbidimetric method, the adhesion was directly examined on chitosan-coated glass plates under light microscope and scanning electron microscope (SEM), and the alpha-granule membrane glycoprotein was detected by fluorescent isothiocyanate (FITC)-conjugated anti-CD61 antibody through flow cytometry. The subsequent epidermal growth factor (EGF), platelet-derived growth factor (PDGF)-AB and transforming growth factor (TGF)-beta1 release from platelets were assayed by ELISA after mixing with chitosan.

RESULTS

The enhancing effects on the platelet adhesion and the aggregation from chitosan were observed. Under both microscopes, the adhesive platelets on the chitosan-coated plates were not only greater in number but also earlier in activation than those on the control plates. With flow cytometry, increased glycoprotein IIIa expression in platelets was detected after chitosan treatment. Greater concentrations of growth factors were measured from PRP after chitosan treatment than after the solvent treatment.

CONCLUSION

Because of the observations of growth factors releasing from activated human platelets after chitosan stimulation, we suggest that chitosan may be an appropriate substitute for thrombin in PRP preparation.

Collagen Scaffolds Reinforced with Biomimetic Composite Nano-Sized Carbonate-Substituted Hydroxyapatite Crystals and Shaped by Rapid Prototyping to Contain Internal Microchannels

The next generation of tissue engineering scaffolds will be made to accommodate blood vessels and nutrient channels to support cell survival deep in the interior of the scaffolds. To this end, we have developed a method that incorporates microchannels to permit the flow of nutrient-rich media through collagen-based scaffolds. The scaffold matrix comprises nano-sized carbonate-substituted hydroxyapatite (HA) crystals internally precipitated in collagen fibers. The scaffold therefore mimics many of the features found in bone. A biomimetic precipitation technique is used whereby a collagen membrane separates reservoirs of calcium and phosphate solutions. The collision of calcium and phosphate ions diffusing from opposite directions results in the precipitation of mineral within the collagen membrane. Transmission electron microscopy analysis showed the dimension of the mineral crystals to be approximately 180 x 80 x 20 nm, indicating that the crystals reside in the intermicrofibril gaps. Electron diffraction indicated that the mineral was in the HA phase, and infrared spectroscopy confirmed type A carbonate substitution. The collagen-HA membrane is then used to make 3-dimensional (3D) scaffolds: the membrane is shredded and mixed in an aqueous-based collagen dispersion and processed using the critical point drying method. Adjusting the pH of the dispersion to 5.0 before mixing the composite component preserved the nano-sized carbonate-substituted HA crystals. Branching and interconnecting microchannels in the interior of the scaffolds are made with a sacrificial mold manufactured by using a 3D wax printer. The 3D wax printer has been modified to print the mold from biocompatible materials. Appropriately sized microchannels within collagen-HA scaffolds brings us closer to fulfilling the mass transport requirements for osteogenic cells living deep within the scaffold.

Chemical modification of chitosan by phosphorylation: an XPS, FT-IR and SEM study

In the present work, the surface of chitosan membranes was modified using a phosphorylation method carried out at room temperature. Phosphorylation may be of particular interest in materials for orthopaedic applications, due to the cation-exchange properties of phosphate functionalities. Phosphate groups chelate calcium ions, thus inducing the deposition of an apatite-like layer known to improve the osteoconduction of polymer-based implants. Additionally, the negatively charged phosphate functionalities, together with the positively charged amine groups from chitosan, are expected to provide chitosan with an amphoteric character, which may be useful as a combinatorial therapeutic strategy, by simultaneously allowing the immobilization of signalling molecules like growth factors. Phosphorylation was carried out at room temperature using the H3PO4/Et3PO4/P2O5/butanol method. Surface characterization was performed by XPS, ATR-FT-IR, and SEM. Cross-sections were analyzed by SEM fitted with EDS. The phosphate content increased with the reaction time, as shown by XPS and ATR-FT-IR, a P/N atomic ratio of 0.73 being obtained after 48 h of treatment. High-resolution XPS spectra regarding C1s, O1s, N1s and P2p are discussed. The introduction of a neutralization step led to a reduction of P content, which pointed out to the presence of phosphates ionically bound to protonated amines, in addition to phosphate esters. EDS analysis of cross-sections revealed a gradual P reduction up to 50% towards the inner part of the membrane.

Biological Evaluation of Chitosan Nanofiber Membrane for Guided Bone Regeneration

BACKGROUND

Chitosan is known as a biodegradable and non-toxic natural polymer that enhances wound healing and bone formation. The aims of this study are to evaluate the biocompatibility of chitosan nanofiber membranes and to examine the effect of the chitosan nanofiber membranes on bone regeneration in rabbit calvarial defects.

METHODS

In vitro cell proliferation tests using human osteosarcoma cell line MG63 and reverse transcription-polymerase chain reaction (RT-PCR) to evaluate the expression of alkaline phosphatase (ALP), collagen, osteocalcin (OCN), and GAPDH were done on chitosan nanofiber membranes. Chitosan nanofiber membranes were implanted in subcutaneous connective tissue and observed for 2, 4, and 6 weeks in rats. Ten-millimeter diameter round cranial defects were made in rabbits and covered by chitosan nanofiber membranes for 4 weeks. Specimens were decalcified and observed by a light microscope.

RESULTS

MG63 cells proliferated for 28 days on the chitosan nanofiber membranes and expressed ALP, collagen, OCN, and GAPDH at 2 weeks. Chitosan nanofiber membranes that were grafted into rat subcutaneous tissue maintained their shape and space for bone regeneration for as long as 6 weeks. No inflammation could be seen on the membrane surface or in the surrounding tissues. In the rabbit calvarial defects, new bone filled the defects and fused to the original old bone in 4 weeks.

CONCLUSIONS

The biocompatibility of the chitosan nanofiber membrane was confirmed, with enhanced bone regeneration and no evidence of an inflammatory reaction. This experiment shows that the novel biodegradable chitosan nanofiber membrane may be useful as a tool for guided bone regeneration.

Studies on the spectroscopic behavior of cryptotanshinone, tanshinone IIA, and tanshinone I

A comparative study on the spectroscopic behavior of cryptotanshinone (CTan), tanshinone IIA (Tan IIA), and tanshinone I (Tan I) has been investigated, including UV-Vis absorption, low temperature phosphorescence (LTP), low temperature fluorescence (LTF), paper substrate-room temperature phosphorescence (PS-RTP), paper substrate-room temperature fluorescence (PS-RTF) and fluorescence in liquid (LF). The effect of pH on the luminescence intensity is discussed. Lifetime and polarization of the LTP and RTP have been examined with phosphorescence lifetime in the range of 0.6-0.9s and polarization in the range of 0.10-0.27. Analytical characteristics of LF, PS-RTF and PS-RTP of CTan, Tan IIA, and Tan I have been studied.

Implantable applications of chitin and chitosan

Chitin, extracted primarily from shellfish sources, is a unique biopolymer based on the N-acetyl-glucosamine monomer. More than 40 years have lapsed since this biopolymer had aroused the interest of the scientific community around the world for its potential biomedical applications. Chitin, together with its variants, especially its deacetylated counterpart chitosan, has been shown to be useful as a wound dressing material, drug delivery vehicle and increasingly a candidate for tissue engineering. The promise for this biomaterial is vast and will continue to increase as the chemistry to extend its capabilities and new biomedical applications are investigated. It is interesting to note that a majority of this work has come from Asia. Japan has been the undisputed leader, but other Asian nations, namely Korea, Singapore, Taiwan and Thailand have also made notable contributions. More recently, China has joined the club to become an increasingly major research source for chitin and chitosan in Asia. This review surveys select works of key groups in Asia developing chitin and chitosan materials for implantable biomedical applications.