Studies on alginate-chitosan microcapsules and renal arterial embolization in rabbits

Encapsulation of quercetin fraction from Musa balbisiana banana blossom in chitosan alginate solution, its optimization and characterizations

This study comprises the isolation of quercetin from the bhimkol banana (Musa balbisiana) blossom, encapsulation, and its characterizations. An isolated quercetin rich fraction was obtained from HPLC followed by column chromatography and subsequently encapsulated with chitosan-alginate polyelectrolyte complex at optimum encapsulation conditions obtained by ant colony optimization. Quercetin fraction and encapsulated quercetin were characterized for their physicochemical properties (by HPLC, FTIR, NMR, XRD, Dynamic Light Scattering, and release study). The yield and purity of isolated quercetin rich fractions were 2.35 ± 0.08 μg/ml and 83.12 ± 0.31 %, respectively. After the optimization of encapsulation, quercetin 0.2 %, sodium alginate 4 %, chitosan 0.5 %, and agitation at 300 rpm were found to be the optimal conditions resulting in higher encapsulation efficiency (EE, 84.54 %). EE was significantly improved by a slight increase in sodium alginate, and agitation. Encapsulated quercetin revealed good pH resistance by releasing 68.27 mg QE/g quercetin in simulated gastric fluid at 60 min. Microbeads of encapsulated quercetin showed the structural bond stretching of encapsulating materials and quercetin in FTIR spectra (stretching at 1511 cm-1, 1380 cm-1, and 1241 cm-1 are attributed to the stretching vibration of CO in aromatic rings, and bending vibration of OH bond in phenols). An average particle size of 2.71 μm exhibited the microgel behavior of microbeads (by XRD). The present study on the underutilized variety of banana blossoms has diverse applications in the food and pharmaceutical industries that will productively exhibit effective drug delivery properties.

Preparation of a modified silk-based gel/microsphere composite as a potential hepatic arterial embolization agent

Transcatheter arterial chemoembolization (TACE) is an effective method for treating hepatocellular carcinoma (HCC). In this study, chitosan (CS), sodium glycerophosphate (GP), and sodium alginate (SA) were used as the main raw materials to develop clinically non-degradable embolization microspheres (Ms). Chitosan/sodium alginate embolization Ms. were generated using an emulsification cross-linking method. The Ms. were then uniformly dispersed in CS/GP temperature-sensitive gels to produce Gel/Ms. composite embolic agents. The results showed that Gel/Ms. had good morphology and a neatly arranged three-dimensional structure, and the Ms. dispersed in the Gel as evidenced by SEM. Furthermore, Gel/Ms. has good blood compatibility, with a hemolysis rate of ≤5 %. The cytotoxicity experiments have also proven its excellent cell compatibility. The degradation rate of Gel/Ms. was 58.869 ± 1.754 % within 4 weeks, indicating that Gel/Ms. had good degradation performance matching its drug release purpose. The Gel/Ms. adheres better at the target site than Ms. alone and releases the drug steadily over a long period, and the maximum release rate of Gel/Ms. within 8 h was 38.33 ± 1.528 %, and within 168 h was 81.266 ± 1.193 %. Overall, Gel/Ms. demonstrate better slow drug release, reduced sudden drug release, prolonged drug action time at the target site, and reduced toxic side effects on the body compared to Gel alone.

Purification, antioxidant activities, encapsulation, and release profile of total flavonoids in Peony seed meal

As potential biomass resources, biomass waste products have been considered worldwide in recent decades. Peony seed meal (PSM) is a kind of agricultural resource waste containing polyphenols, in particular flavonoids. In this study, the total flavonoids of PSM were extracted and purified by AB‐8 macroporous resin (MR), the antioxidant activities of three extract fractions were evaluated, and the total flavonoids were encapsulated with alginate and chitosan by the complex coacervation method. After purification, the yield of total flavonoids was 11.32% and the content in the product increased to 42.89% ± 2.66. The antioxidant activities of three fractions on ^·OH, DPPH, and ABTS assays exhibited the following descending order: ethanol elution fraction (ELF) > ethyl acetate extract fraction (EAF) > ethanol extract fraction (EEF). The single‐factor assay showed that the encapsulated total flavonoid microcapsules (EFMs) were prepared with a chitosan concentration of 10 mg/ml, a sodium alginate concentration of 30 mg/ml, a calcium chloride concentration of 50 mg/ml, a ratio of sodium alginate to total flavonoids of 1:3, a flavonoid concentration of 40 mg/ml, and an encapsulation yield of 80.7%. Most microcapsules are smooth‐faced, spherical and uniform in size ranging from 2 to 3 mm in diameter. In vitro release studies suggested that the EFM was stable at pH 1.2 and dissolved at pH 7.5. The result indicated that the EFM is worthy for the development of functional foods and supplements, and PSM could be a potential resource in the food and pharmaceutical industries.

Oral Probiotic Vaccine Expressing Koi Herpesvirus (KHV) ORF81 Protein Delivered by Chitosan-Alginate Capsules Is a Promising Strategy for Mass Oral Vaccination of Carps against KHV Infection

Koi herpesvirus (KHV) is highly contagious and lethal to cyprinid fish, causing significant economic losses to the carp aquaculture industry, particularly to koi carp breeders. Vaccines delivered through intramuscular needle injection or gene gun are not suitable for mass vaccination of carp. So, the development of cost-effective oral vaccines that are easily applicable at a farm level is highly desirable. In this study, we utilized chitosan-alginate capsules as an oral delivery system for a live probiotic (Lactobacillus rhamnosus) vaccine, pYG-KHV-ORF81/LR CIQ249, expressing KHV ORF81 protein. The tolerance of the encapsulated recombinant Lactobacillus to various digestive environments and the ability of the probiotic strain to colonize the intestine of carp was tested. The immunogenicity and the protective efficacy of the encapsulated probiotic vaccine was evaluated by determining IgM levels, lymphocyte proliferation, expression of immune-related genes, and viral challenge to vaccinated fish. It was clear that the chitosan-alginate capsules protected the probiotic vaccine effectively against extreme digestive environments, and a significant level (P < 0.01) of antigen-specific IgM with KHV-neutralizing activity was detected, which provided a protection rate of ca. 85% for koi carp against KHV challenge. The strategy of using chitosan-alginate capsules to deliver probiotic vaccines is easily applicable for mass oral vaccination of fish.IMPORTANCE An oral probiotic vaccine, pYG-KHV-ORF81/LR CIQ249, encapsulated by chitosan-alginate capsules as an oral delivery system was developed for koi carp against koi herpesvirus (KHV) infection. This encapsulated probiotic vaccine can be protected from various digestive environments and maintain effectively high viability, showing a good tolerance to digestive environments. This encapsulated probiotic vaccine has a good immunogenicity in koi carp via oral vaccination, and a significant level of antigen-specific IgM was effectively induced after oral vaccination, displaying effective KHV-neutralizing activity. This encapsulated probiotic vaccine can provide effective protection for koi carp against KHV challenge, which is handling-stress free for the fish, cost effective, and suitable for the mass oral vaccination of koi carp at a farm level, suggesting a promising vaccine strategy for fish.

Advances in Biomaterials and Technologies for Vascular Embolization

Minimally invasive transcatheter embolization is a common nonsurgical procedure in interventional radiology used for the deliberate occlusion of blood vessels for the treatment of diseased or injured vasculature. A wide variety of embolic agents including metallic coils, calibrated microspheres, and liquids are available for clinical practice. Additionally, advances in biomaterials, such as shape-memory foams, biodegradable polymers, and in situ gelling solutions have led to the development of novel preclinical embolic agents. The aim here is to provide a comprehensive overview of current and emerging technologies in endovascular embolization with respect to devices, materials, mechanisms, and design guidelines. Limitations and challenges in embolic materials are also discussed to promote advancement in the field.

Self-Regulated Carboxyphenylboronic Acid-Modified Mesoporous Silica Nanoparticles with "Touch Switch" Releasing Property for Insulin Delivery

Glucose-responsive insulin delivery systems, which can maintain a stable level of blood glucose, have been proposed as a promising method to treat diabetes. Such systems can reduce potential toxicity and enhance patient compliance compared to traditional therapies. Accordingly, we designed a mesoporous silica nanoparticle (MSN)-based glucose-sensitive and self-regulated drug release system to achieve the goal of long circulation and "touch switch" in vivo. In this system, carboxyphenylboronic acid (CPBA) was first modified on the surface of MSN using amidation reaction. Insulin (INS) was then loaded in the channels of MSN (CPBA-MSN/INS) through physical adsorption, and sodium alginate (SA) was introduced onto the surface of the CPBA-MSN/INS nanoparticles as the gatekeeper via amidation reaction (SA/CPBA-MSN/INS). We found the drug loading capacity of INS was 261 mg/g. In the normal range of blood glucose, INS was scarcely released due to the reversible covalent interaction between 1,2-diols of SA and CPBA. Within the high concentration of glucose, the boronate esters could be dissociated, which results in the mesoporous channels opening and the release of INS. In vivo experiments on diabetic mice showed SA/CPBA-MSN/INS sustained a normal blood glucose level for up to 12 h with a single dose. Moreover, the lipid metabolism disorder and organ damage of diabetic mice were alleviated after treatment with SA/CPBA-MSN/INS. Therefore, SA/CPBA-MSN/INS characterized by an "on-off" regulated drug release property and high biosafety shows promise for applications in diabetes treatment.

Chitosan-Based Multifunctional Platforms for Local Delivery of Therapeutics

Chitosan has been widely used as a key biomaterial for the development of drug delivery systems intended to be administered via oral and parenteral routes. In particular, chitosan-based microparticles are the most frequently employed delivery system, along with specialized systems such as hydrogels, nanoparticles and thin films. Based on the progress made in chitosan-based drug delivery systems, the usefulness of chitosan has further expanded to anti-cancer chemoembolization, tissue engineering, and stem cell research. For instance, chitosan has been used to develop embolic materials designed to efficiently occlude the blood vessels by which the oxygen and nutrients are supplied. Indeed, it has been reported to be a promising embolic material. For better anti-cancer effect, embolic materials that can locally release anti-cancer drugs were proposed. In addition, a complex of radioactive materials and chitosan to be locally injected into the liver has been investigated as an efficient therapeutic tool for hepatocellular carcinoma. In line with this, a number of attempts have been explored to use chitosan-based carriers for the delivery of various agents, especially to the site of interest. Thus, in this work, studies where chitosan-based drug delivery systems have successfully been used for local delivery will be presented along with future perspectives.

Remote controlled drug release from multi-functional Fe3O4/GO/Chitosan microspheres fabricated by an electrospray method

The construction of multifunctional microspheres for remote controlled drug release requires the exquisite selection of composite materials and preparation approaches. In this study, chitosan, an amino polysaccharide, was blended with inorganic nanocomponents, Fe₃O₄ and graphene oxide (GO) and electrosprayed to fabricate uniform microspheres with the diameters ranging from 100μm to 1100μm. An anti-cancer drug, doxorubicin (DOX), was loaded to the microspheres by an adsorption or embedding method. The microsphere is responsive to magnetic fields due to the presence of Fe₃O₄, and the incorporation of GO enhanced the drug loading capacity. The fast stimuli-responsive release of DOX can be facilely controlled by using NIR irradiation due to the strong photo-thermal conversion of Fe₃O₄ and GO_. In addition, ultrasound was used as another external stimulus for DOX release. The results suggest the Fe₃O₄/GO/Chitosan microspheres fabricated by the electrospray method provide an efficient platform for remote controlled drug release, which may have potential applications in drug eluting microspheres.

Arming embolic beads with anti-VEGF antibodies and controlling their release using LbL technology

Transarterial chemoembolization (TACE) is used to treat various types of hypervascular tumors such as hepatocellular carcinoma and renal cancer. However, embolization and blocking of blood vessels nourishing a tumor mass evokes an angiogenic response due to the secretion of vascular endothelial growth factor (VEGF), which results in the formation of new blood vessels and eventually limitation in therapeutic efficacy. The presented work investigates the feasibility of loading the clinically used embolic beads (DC Bead®) with Bevacizumab (BEV), an anti-VEGF antibody, and control its release kinetics via Layer-by-Layer (LbL) coating. This strategy has the aim to achieve high, localized and sustained concentrations of BEV at the tumor site and reduce drug exposure in the systemic circulation. High loading of BEV on lyophilized beads of about 76mg BEV/bead vial was achieved. LbL coating was carried out by depositing alternating layers of the biocompatible polymers alginate and poly-L-lysine. Coating was proven successful by monitoring the reversal of zeta potential after addition of each layer. Morphological changes of the bead surface before and after coating were illustrated using SEM imaging. Moreover, release profiles from different formulations were studied and results showed that optimizing the number of deposited layers effectively slows the release of BEV for three days. Activity of released BEV was studied in different 2D and 3D cell based assays. Released BEV fractions showed comparable activity to fresh BEV solution used as control after 3days. In conclusion, our results suggest the opportunity for loading anti-VEGF antibodies on commercially available embolic beads to increase the efficacy of TACE of hypervascular tumors.

Alginate Microspheres Containing Temperature Sensitive Liposomes (TSL) for MR-Guided Embolization and Triggered Release of Doxorubicin

Objective

The objective of this study was to develop and characterize alginate microspheres suitable for embolization with on-demand triggered doxorubicin (DOX) release and whereby the microspheres as well as the drug releasing process can be visualized in vivo using MRI.

Methods and Findings

For this purpose, barium crosslinked alginate microspheres were loaded with temperature sensitive liposomes (TSL/TSL-Ba-ms), which release their payload upon mild hyperthermia. These TSL contained DOX and [Gd(HPDO3A)(H₂O)], a T₁ MRI contrast agent, for real time visualization of the release. Empty alginate microspheres crosslinked with holmium ions (T₂* MRI contrast agent, Ho-ms) were mixed with TSL-Ba-ms to allow microsphere visualization. TSL-Ba-ms and Ho-ms were prepared with a homemade spray device and sized by sieving. Encapsulation of TSL in barium crosslinked microspheres changed the triggered release properties only slightly: 95% of the loaded DOX was released from free TSL vs. 86% release for TSL-Ba-ms within 30 seconds in 50% FBS at 42°C. TSL-Ba-ms (76 ± 41 μm) and Ho-ms (64 ± 29 μm) had a comparable size, which most likely will result in a similar in vivo tissue distribution after an i.v. co-injection and therefore Ho-ms can be used as tracer for the TSL-Ba-ms. MR imaging of a TSL-Ba-ms and Ho-ms mixture (ratio 95:5) before and after hyperthermia allowed in vitro and in vivo visualization of microsphere deposition (T₂*-weighted images) as well as temperature-triggered release (T₁-weighted images). The [Gd(HPDO3A)(H₂O)] release and clusters of microspheres containing holmium ions were visualized in a VX₂ tumor model in a rabbit using MRI.

Conclusions

In conclusion, these TSL-Ba-ms and Ho-ms are promising systems for real-time, MR-guided embolization and triggered release of drugs in vivo.

Investigation of acetylated chitosan microspheres as potential chemoembolic agents

The aim was to investigate the potential of chitosan microspheres (CMs) with different acetylation using as a chemoembolic agent. Chitosan microspheres (CMs) were prepared via water-in-oil (W/O) emulsification cross-linking method, and acetylated chitosan microspheres (ACMs) were obtained by acetylation of CMs. Next, we characterized the morphology, size, composition and degrees of deacetylation using scanning electron microscopy (TEM), dynamic laser light scattering (DLS), and Fourier transform infrared spectrometer (FTIR). All microspheres had smooth surfaces and good mechanical flexibility, and all could pass through a 5F catheter. The swelling rate (SR) of CMs decreased significantly with the increase of pH (4.0-10.0) but ACMs did not change under the same conditions. Protein absorption assays suggested that albumin was more greatly adsorbed on CMs than on ACMs. Furthermore, CMs caused more blood clots than ACMs. ACMs caused hemolysis less than CMs (<5% of the time). Data indicated that ACMs had more hemocompatibility. Cytotoxicity tests indicated that ACMs initially had less cell attached proliferation but increased with incubation. In contrast, the relative growth rate of mouse embryo fibroblasts (MEFs) on CMs decreased gradually. The results suggested that ACMs could stimulate the growth of MEFs, and CMs were not cytotoxic to MEFs. Thus, ACMs were more biocompatible with greater potential to be used as chemoembolic material.

Preparation of the core-shell structure adriamycin lipiodol microemulsions and their synergistic anti-tumor effects with diethyldithiocarbamate in vivo

We prepared the core-shell structure adriamycin lipiodol microemulsions (ADM-CSLMs) and evaluated their in vivo antitumor effects in combination with Diethyldithiocarbamate (DDC). Two types of ADM-CSLMs, adriamycin liposome-lipiodol microemulsion(ADM-LLM) and adriamycin microsphere lipiodol microemulsion (ADM-MLM), were prepared through the emulsification method. The drug loading and encapsulation efficiency of ADM-CSLMs were measured by the high-performance liquid chromatograph (HPLC). The size and shape of the ADM-CSLMs were determined by an atom force microscopy (AFM), a transmission electron microscopy (TEM), and a particle size analyzer, respectively. The synergistic effects of DDC and ADM-CSLMs for cancer treatment of carcinoma drug-resistance cell was evaluated by the MTT method, the activation of superoxide dismutase (SOD) was detected by chemiluminescence, and the ADM accumulation in cells was measured by flow cytometry. Walker-256 carcinoma was transplanted to the livers of the male SD rats, ADM-CSLMs were administrated to the livers of the rats by intervention hepatic artery embolization through microsurgery. The tumor growth and animal survival were evaluated. The results show that the average diameter of ADM-LLM and ADM-MLM were 4.23 ± 1.2 μm and 4.67 ± 1.4 μm, respectively, and their ADM encapsulation efficiency were 83.7% and 87.2% with respect to loading efficiency of 82 μg/ml and 91 μg/ml. The tumor growth and animal survival in two of the ADM-CSLMs combined with DDC groups were significantly higher than that of ADM only treatment, ADM liposome combined with DDC (P < 0.01), as well as the ADM microsphere combined with DDC (P < 0.01). Therefore, ADM-CSLMs are useful carriers for the treatment of carcinoma and their anti-tumor effect can be enhanced by DDC in a suitable concentration.

Review: doxorubicin delivery systems based on chitosan for cancer therapy

Objectives

This review sheds insight into an increasingly popular polymer that has been widely explored as a potential drug delivery system. The abundant, biodegradable and biocompatible polysaccharide chitosan, with many other favourable properties, has been favoured as a drug delivery system for the purposes of encapsulating and delivery of doxorubicin with reduced side-effects.

Key findings

Doxorubicin is frequently used as a frontline chemotherapeutic agent against a variety of cancers. It has largely been able to demonstrate anti-tumour effects, though there are major shortfalls of doxorubicin, which include serious side-effects such as cardiomyopathy and myelosuppression, and also an ever-present danger of extravasation during drug administration. In view of this, drug delivery systems are currently being explored as alternative methods of drug delivery in a bid to more effectively direct doxorubicin to the specific lesion site and reduce its systemic side-effects. Liposomes and dendrimers have been tested as potential carriers for doxorubicin; however they are not the focus of this review.

Summary

Recent advancements in doxorubicin and chitosan technology have shown some preliminary though promising results for cancer therapy.

Phosphorylcholine-Containing Polymers for Use in Cell Encapsulation

A model system for encapsulation of pancreatic islets which has potential properties for improving biocompatibility and immunosuppression was investigated. In vitro and in vivo studies have shown that phosphorylcholine-containing polymers have high biocompatibility due to low adsorption of proteins and reduced thrombus formation. Encapsulation of islets isolated from rats with a compound membrane composed of phosphorylcholine-containing polymers and cellulose acetate led to rapid insulin production and diffusion across the membrane in response to glucose challenge. The phosphorylcholine-containing polymer had a molecular weight of about 1.3 x 10(4) Da. The polymer-coated membrane excluded larger molecules such as IgG (molecular weight 150 kDa), thereby acting as a physical immuno-barrier, but allowed smaller molecules such as glucose and insulin to pass through.

Morfologia de hidrogéis-ipn termo-sensíveis e ph-responsivos para aplicação como biomaterial na cultura de células

No presente trabalho, foram sintetizados hidrogéis com ambas as propriedades, termo-sensíveis e pH-responsivos, pela formação de redes de alginato de cálcio (alginato-Ca) dentro de redes de poli(N-Isopropil Acrilamida) (PNIPAAm), resultando em um sistema IPN (sistema de redes poliméricas interpenetradas). Através das análises por microscopia de varredura eletrônica (MEV) e ensaios de intumescimento foi possível observar que os hidrogéis IPN exibiram forte contração quando aquecidos acima da LCST (temperatura critica inferior de solubilização) da PNIPAAm, ou seja, acima de temperaturas de 30-35 ºC. Observou-se ainda que devido à contração do hidrogel, houve uma diminuição significativa nos tamanhos de poros os quais foram observados pelas micrografias. Observou-se também que no intervalo de pH estudado os hidrogéis de IPN sofreram significativa variação da estrutura com a variação desse parâmetro. Tal efeito foi atribuído à presença de grupos químicos carregados com alginato, os quais possuem carga elétrica negativa. Os resultados indicaram que o hidrogel formado por alginato-Ca e PNIPAAm possuíram características especificas após variação de pH e temperatura, e que tais características são derivadas dos compostos individuais envolvidos na síntese. Nesse caso, as propriedades de alginato-Ca e PNIPAAm livres foram preservadas dentro do hidrogel. Tal hidrogel ficou mais resistente à aplicação de uma tensão de compressão. Como conclusão, observou-se que os hidrogéis apresentaram morfologia característica para variações controladas de pH e temperatura, podendo ser eficientemente aplicados como biomaterial na cultura de células.

Genipin Cross-Linked Polymeric Alginate-Chitosan Microcapsules for Oral Delivery: In-Vitro Analysis

We have previously reported the preparation of the genipin cross-linked alginate-chitosan (GCAC) microcapsules composed of an alginate core with a genipin cross-linked chitosan membrane. This paper is the further investigation on their structural and physical characteristics. Results showed that the GCAC microcapsules had a smooth and dense surface and a networked interior. Cross-linking by genipin substantially reduced swelling and physical disintegration of microcapsules induced by nongelling ions and calcium sequestrants. Strong resistance to mechanical shear forces and enzymatic degradation was observed. Furthermore, the GCAC membranes were permeable to bovine serum albumin and maintained a molecular weight cutoff at 70 KD, analogous to the widely studied alginate-chitosan, and alginate-poly-L-lysine-alginate microcapsules. The release features and the tolerance of the GCAC microcapsules in the stimulated gastrointestinal environment were also investigated. This GCAC microcapsule formulation offers significant potential as a delivery vehicle for many biomedical applications.

Preparation of doxorubicin-containing chitosan microspheres for transcatheter arterial chemoembolization of hepatocellular carcinoma

A new form of doxorubicin hydrochloride (DRH)-containing chitosan microspheres (CMs) was prepared by employing an expanding-loading-shrinking (E-L-S) process. One hundred mg of pre-formed CMs were soaked in absolute ethanol and then placed in reduced pressure (the expanding process). Ten mg of DRH (2 mg ml(-1)) were added into the expanded CMs (the loading process). Next the microspheres were freeze-dried (the shrinking process). As a result of this E-L-S process, 10% (w/w) DRH-containing CMs (DRH-CM) were made. During 7 days, 22.6% of the DRH was observed to be released on the in vitro drug release study. In addition, these new DRH-CMs could be used for transcatheter arterial chemoembolization (TACE) procedure in VX2 hepatic tumour models of rabbit and the anti-tumour effects of DRH-CMs were investigated. On the post-CT scan 7 days after the TACE, total infarctions of the VX2 tumour were observed in 5 rabbits among the 6 total rabbits.

Preparation and characterization of Mitomycin-C loaded chitosan-coated alginate microspheres for chemoembolization

Mitomycin-C loaded and chitosan-coated alginate microspheres were prepared for use in chemoembolization studies. In this respect, first alginate microspheres were prepared by using a spraying method using an extrusion device with a small orifice and following suspension cross-linking in an oil phase. Chitosan-coating onto the alginate microspheres was achieved by polyionic complex formation between alginate and chitosan. CaCl(2) was used as a cross-linker for alginate microspheres. The obtained chitosan-coated alginate microspheres were spherical shaped and approximately 100-400 microm average size. The microspheres were evaluated based on their swellability and the swelling ratio was changed between 50-280%. CaCl(2) concentration, stirring rate, chitosan molecular weight, chitosan concentration and time for coating with chitosan were selected as the effective parameters on microsphere size and swelling ratio. Equilibrium swellings were achieved in approximately 30 min. On the other hand, chitosan molecular weight, chitosan concentration and time for coating with chitosan were found as the most effective parameters on both drug loading ratio and release studies. Maximum drug loading ratio of 65% was achieved with high molecular weight (HMW) chitosan, highest chitosan concentration (i.e. 1.0% v/v) and shortest time for coating with chitosan (i.e. 1 h) values.

Preparation and blood coagulation evaluation of chitosan microspheres

Cross-linked chitosan microspheres (40-100 microm) with smooth surface were prepared by the methods of emulsification and ethanol coagulant. FTIR results showed that the cross-linking reaction occurred on the amino groups of chitosan molecules. The swelling characteristic of chitosan microspheres was influenced by the environment pH, being generally greater at low rather than higher pH values. The coagulation properties of chitosan microspheres were evaluated by dynamic blood clotting, platelet adhesion and activation, erythrocyte adhesion, hemolysis, and protein absorption assays. Chitosan microspheres can shorten the clotting time and induce the adhesion and activation of platelets. But the shortening of clotting time by chitosan microspheres may be related to not only platelet aggregation, but also erythrocyte aggregation. Take together, chitosan microspheres may be potential use as thrombospheres.

Application of gold nanoparticles to microencapsulation of thioridazine

Thioridazine-containing ethyl cellulose (EC) microcapsules were prepared in the presence of gold nanoparticles via the W/O/W emulsification solvent-evaporation method. The gold nanoparticles have been verified as human safe and the nondestructive physisorption of thioridazine on gold nanoparticles was corroborated with the time-of-flight second ion mass spectrometry measurements. The morphology of the formed microcapsules (ETA, containing EC, Thioridazine and Au) changed substantially because of the presence of gold nanoparticles. In addition to a prolonged controlled release, these ETA microcapsules had an enhanced thioridazine encapsulation with an efficiency over one and half times that of the microcapsules (ET) containing no nanogold particles. While data of the release kinetics for ET microcapsules fitted the apparent first-order model, corresponding data for ETA microcapsules agreed better with the Higuchi model indicating a uniform distribution of thioridazine in the monolithic-type microcapsules.

Ibuprofen-loaded nanoparticles prepared by a co-precipitation method and their release properties

A co-precipitation method was established to fabricate nano-scale core-shell particles, by which poor water-soluble drugs can be effectively dispersed with rather good stability during storage. Exemplified with formation of ibuprofen (Ib) nanoparticles stabilized by DEAE dextran (Ddex), the process includes precipitation of Ib in a supersaturated solution and deposition of Ddex onto the precipitated Ib particles through electrostatic interaction. Characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS) and zeta potential, the core-shell structure of the particles formed at pH 6.0 with a Ddex/Ib weight ratio of 5:1 was identified with Ib being the core and Ddex being the shell. As a comparison, particles formed at other pH values and other Ddex/Ib ratios were also studied. Along with increase of the Ddex/Ib ratio or pH value of the final aqueous solution, the particle size was decreased, demonstrating that the particle sizes could be readily tuned by variation of the fabrication parameters. At conditions that the Ib concentration was lower than its supersaturated value, for example at higher pH value, instead of co-precipitation mechanism, forces such as electrostatic complexation dominate the formation of Ddex-Ib particles. Moreover, drug entrapment was mainly dependent on the Ib solubility regardless of the ratio between Ddex and Ib, while the drug content was decreased as a function of Ddex/Ib ratio. In vitro release studies showed that the loaded Ib could be again released in a burst manner during the initial stage, followed with a slow rate. The final released amount of Ib showed a positive correlation with the bulk pH value, e.g. approximately 60, 80 and 90% of the loaded Ib were released in pH 1.0, 5.8 and 7.4 buffered solutions after incubation for 40 h, respectively.

Indomethacin release from ion-exchange microspheres: impregnation with alginate reduces release rate

Ion-exchange microspheres (MS) designed as a drug delivery system for embolization coupling ability to occlude vessels and chemotherapy were used to evaluate a manufacturing process allowing to control the drug release rate through reduction of diffusion rate of the drug within the particle by impregnation of calcium alginate inside the porous MS. Impregnation was performed by diffusion of sodium alginate inside DEAE-Trisacryl(R) MS, dispersion of the MS in deionised water and gelling alginate by adding CaCl(2) to the dispersed MS. Studied parameters were alginate concentration, alginate diffusion time and calcium concentration. Indomethacin was loaded into the MS by eluting an aqueous indomethacin solution through a chromatographic column packed with impregnated MS. Indomethacin loading was reduced by alginate. Swelling studies showed indomethacin loading enhanced the hydrophobicity of MS while impregnation had no effect. This had an incidence on indomethacin release rate, which was assessed using the rapid elution of PBS through loaded impregnated MS packed in a column. Indomethacin loading reduced its own rate of release. MS impregnated with 2% w/v alginate gelled with a 40 mM calcium solution presented the lower release rate. This work indicated the manufacturing conditions to display a calcium alginate matrix effect on indomethacin release from DEAE-Trisacryl MS.

Properties of calcium-induced gel beads prepared with alginate and hydrolysates

Calcium-induced alginate gel beads (Alg-Ca) containing alginate hydrolysate, such as the guluronic acid block (GB), was prepared and the drug release profiles were investigated under simulated gastrointestinal conditions. The addition of GB to Alg-Ca altered its rheological properties. A model drug (hydrocortisone) was incorporated at 78% of its theoretical yield within the dried Alg-Ca containing 5% GB and it was gradually released from the beads in JP XIV 1st medium for disintegration test (pH 1.2), while it was rapidly released with disintegration of the gel matrix in JP XIV 2nd medium (pH 6.8). In contrast, for Alg-Ca containing GB and chitosan, disintegration was not observed in these media and the drug release rate was markedly different. These results demonstrate that the release profiles of drugs incorporated into Alg-Ca can be controlled by adding these polysaccharides.

Preparation of alginate/chitosan microcapsules and enteric coated granules of mistletoe lectin

The aqueous extract of European mistletoe (Viscum album, L.) has been used in cancer therapy. The purified mistletoe lectins, main components of mistletoe, have demonstrated cytotoxic and immune-system-stimulating activities. Korean mistletoe (Viscum album L. coloratum), a subspecies of European mistletoe, has also been reported to possess anticancer and immunological activities. A galactose- and N-acetyl-D-galactosamine-specific lectin (Viscum album L. coloratum agglutinin, VCA) with Mr 60 kDa was isolated from Korean mistletoe. Mistletoe preparations have been given subcutaneously due to the low stability of lectin in the gastrointestinal (GI) tract. In the present study, we investigated the possibility of alginate/chitosan microcapsules as a tool for oral delivery of mistletoe lectin. In addition, our strategy has been to develop a system composed of stabilizing cores (granules), which contain mistletoe lectin, extract or powder, coated by a biodegradable polymer wall. Our results indicated that successful incorporation of VCA into alginate/chitosan microcapsules has been achieved and that the alginate/chitosan microcapsule protected the VCA from degradation at acidic pH values. And coating the VCA with polyacrylic polymers, Eudragit, produced outstanding results with ideal release profiles and only minimal losses of cytotoxicity after manufacturing step. The granules prepared with extract or whole plant produced the best results due to the stability in the extract or whole plant during manufacturing process.