Dual-Responsive Alginate Hydrogel Constructed by Sulfhdryl Dendrimer as an Intelligent System for Drug Delivery

Intelligent stimulus-triggered release and high drug-loading capacity are crucial requirements for drug delivery systems in cancer treatment. Based on the excessive intracellular GSH expression and pH conditions in tumor cells, a novel glutathione (GSH) and pH dual-responsive hydrogel was designed and synthesized by conjugates of glutamic acid-cysteine dendrimer with alginate (Glu-Cys-SA) through click reaction, and then cross-linked with polyethylene glycol (PEG) through hydrogen bonds to form a 3D-net structure. The hydrogel, self-assembled by the inner disulfide bonds of the dendrimer, is designed to respond to the GSH heterogeneity in tumors, with a remarkably high drug loading capacity. The Dox-loaded Glu-Cys-SA hydrogel showed controlled drug release behavior, significantly with a release rate of over 76% in response to GSH. The cytotoxicity investigation indicated that the prepared DOX-loaded hydrogel exhibited comparable anti-tumor activity against HepG-2 cells with positive control. These biocompatible hydrogels are expected to be well-designed GSH and pH dual-sensitive conjugates or polymers for efficient anticancer drug delivery.

Development and statistical optimization of alginate-Neusilin US2 micro-composite beads to elicit gastric stability and sustained action of hesperidin

The Alginate-Neusilin US2 micro-composite (MC) beads were fabricated and optimized for oral delivery of hesperidin (HES). A 32 full factorial design encompassing independent variables (factors) such as the concentration of sodium alginate (X1), and Neusilin US2 (X2) and dependant variables (response) such as particle size (Y1), entrapment efficiency (Y2), and swelling degree (Y3). Nine batches were prepared by formulation design employing statistical software JMP 13.2.1. The multiple regression analysis (MLRA) was carried to explore the influence of factor over responses. Further, a prediction profiler was used to trace the optimum concentration of factors based on desirable responses. The optimized beads (OF) were characterized for their morphology and size by motic microscopy and scanning electron microscopy. In vitro release, kinetic studies were performed in simulated gastric and intestinal fluids. In vivo pharmacokinetic studies revealed better absorption of HES from optimized beads (OF) compared to HES suspension which could be due to the prevention of acidic degradation of HES in the stomach. The estimated shelf life of OF formulation was found to be 3.86 years suggested better stability after fabrication. In a nutshell, the developed micro-composite beads of HES could be a better alternative for promising oral sustained delivery of HES.

Alginate based tamoxifen/metal dual core-folate decorated shell: Nanocomposite targeted therapy for breast cancer via ROS-driven NF-κB pathway modulation

Breast cancer endocrine resistance prevents unleashing full capabilities of Tamoxifen (TMX), besides TMX off-target side effects on healthy tissue. In this study, we engineered TMX nanocomposite via co-loading it on alginate-based silver nanoparticles and embedding within folic acid-polyethylene glycol surface conjugate. The coating process was done by w/o/w double emulsion method. To confirm the silver nanoparticles formation, UV spectroscopy, XRD and TEM analysis were carried out. TEM results confirmed the core-shell structure of folate targeted nanocomposite with approximate average diameter of 66 nm, the nanocomposite structures were characterized by FTIR, TGA and SEM. By comparing with the non-targeted formula, folate decorated formula had 12-folds lowered IC₅₀ value and 12.5-14-fold higher cancer cells toxic selectivity index. Also, after 4 h treatment, both fluorescence microscopic and flow cytometric analysis indicated higher intracellular accumulation of folic acid conjugated formula on MCF-7 cancer cells than the non-targeted one with 3.44-folds. The breast cancer cytotoxic effects of this metal-endocrine nanocomposite formula could be explained by the induction of reactive oxygen species (ROS), down regulation of survival oncogenic genes (BCL-2 and Survivin) and the accumulation of MCF-7 cells in G2/M phase. All these data confirm the efficiency and efficacy of the formulated nanocomposite as future treatment for breast cancer.

Silk fibroin/sodium alginate composite porous materials with controllable degradation

In this study, silk fibroin (SF)/sodium alginate (SA) porous materials (PMs) with different blend ratios were generated using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) as crosslinking agent by a simple freeze-dried method. Degradation experiment of SF/SA PMs have been systematically investigated up to 18 days in Collagenase IA solution at 37 °C, Phosphate buffer saline (PBS) solution without enzyme was used as a control. The results showed SF/SA 50/50 PMs exhibited a lowest rate of weight loss, about 68% of the weight retained within 18 d in Collagenase IA solution. SEM images indicated Collagenase IA can degrade fibroin leading to collapse of the pure SF PMs, while SF/SA 50/50 PMs still possessed integrity of pore structure during enzyme degradation with increasing exposure time. The crystalline structure of the SF in the SF/SA PMs changed to silk II after degradation for 18 d. Furthermore, the results of the in vivo degradation by subcutaneous implantation in rats showed that all PMs can be degraded at different levels, and exhibited good subcutaneous histocompatibility to the host animals. The degradability was strongly correlated to the blend ratios in a series of SF/SA composite PMs, and insights gained in this study can serve as a guide to match desired degradation behavior with specific applications for the SF/SA composite PMs.

Soy isoflavone-loaded alginate microspheres in thermosensitive gel base: attempts to improve wound-healing efficacy

OBJECTIVES

This study aims to develop thermosensitive gel containing soy isoflavone (antioxidant and anti-inflammatory natural agent) alginate microspheres for enhancement of wound-healing performance.

METHODS

Soy isoflavone microspheres were prepared by ionic cross-linking method and optimized using the Box-Behnken optimization design. Formulations were characterized in terms of particle size, encapsulation efficiency and equilibrium swelling degree. The optimized formula was incorporated in Pluronic F127 gel base and examined for in vivo wound-healing efficacy.

KEY FINDINGS

Results showed mean particle size between 18 and 25 μm, encapsulation efficiency of over 75% and equilibrium swelling degree over 1.9. Thermal analysis indicated interaction between alginate and CaCl2 and embedding of soy isoflavone in microspheres. In vivo wound-healing efficacy showed significant advance in re-epithelization, mature collagen synthesis and proangiogenesis. Immunohistochemical investigation exhibited promising alpha-smooth muscle actin immunopositive cells expression, fibroblast activation and expression of proliferating cell nuclear antigen (proliferation marker) in the epidermis and in the dermis.

CONCLUSIONS

The developed formulation would appear to be a promising topical preparation for accelerating healing process.

Injectable basic fibroblast growth factor-loaded alginate/hyaluronic acid hydrogel for rejuvenation of geriatric larynx

Increase in the geriatric population has led to an increase in the number of elderly patients with laryngeal atrophy and dysfunction. Symptoms of voice change, dysphagia, and aspiration pneumonia negatively influence patient's health status, quality of life, and life span. Injection laryngoplasty used to treat laryngeal dysfunctions does not recover intrinsic functions of the larynx. Thus, we fabricated an injectable basic fibroblast growth factor (bFGF)-loaded alginate (ALG)/hyaluronic acid (HA) hydrogel for inducing rejuvenation of geriatric laryngeal muscles. Optimal in situ-forming bFGF-loaded ALG/HA hydrogel for injection laryngoplasty was prepared and the release profile of bFGF was analyzed. For in vivo analysis, the bFGF-loaded ALG/HA hydrogel was injected into the laryngeal muscles of 18-month-old Sprague-Dawley rats. The rejuvenation efficacy of bFGF-loaded ALG/HA hydrogel in geriatric laryngeal muscle tissues 4- and 12-weeks post-injection was evaluated by quantitative polymerase chain reaction (qPCR), histology, immune-fluorescence staining and functionality analysis. The bFGF-loaded ALG/HA hydrogel induced an increase in the expression of myogenic regulatory factor-related genes, hypertrophy of muscle fiber, proliferation of muscle satellite cells, and angiogenesis and decreased interstitial fibrosis. Administration of the bFGF-loaded ALG/HA hydrogel caused successful glottal gap closure. Thus, the bFGF-loaded ALG/HA hydrogel could be a promising candidate for laryngoplasty aimed at rejuvenating geriatric larynx. STATEMENT OF SIGNIFICANCE: In this manuscript, optimal in situ-forming bFGF-loaded ALG/HA hydrogel for injection laryngoplasty was prepared and the release profile of bFGF was analyzed. Herein, we introduced the materials and methods of injection laryngoplasty for geriatric rat experiment. In addition, we studied effects of bFGF-loaded ALG/HA hydrogel on the therapeutic rejuvenation of geriatric rat larynx. The bFGF-loaded ALG/HA hydrogel induced an increase in the expression of myogenic regulatory factor-related genes, hypertrophy of muscle fiber, proliferation of muscle satellite cells, and angiogenesis and decreased interstitial fibrosis. Furthermore, our functional analysis through the high-speed camera setup demonstrated that the administration of the bFGF-loaded ALG/HA hydrogel induced successful glottal gap closure. Thus, the bFGF-loaded ALG/HA hydrogel could be a promising candidate for injection laryngoplasty with therapeutic effects.

Radiopaque and uniform alginate microspheres loaded with tantalum nanoparticles for real-time imaging during transcatheter arterial embolization

One restriction to the development and application of transcatheter arterial chemoembolization (TACE) therapy is the lack of an inherently radiopaque embolic whose location and distribution can be precisely visualized in real time and be used for non-invasive examination after surgery. Methods: A one-step electrospray method was developed to fabricate calcium alginate microspheres loaded with tantalum nanoparticles (Ta@CaAlg). The parameters of electrospraying were assessed. The in vivo X-ray imaging capability and embolic effect of Ta@CaAlg microspheres were evaluated in the renal arteries of normal rabbits by digital radiography and computed tomography. Doxorubicin hydrochloride (Dox) was chosen as a model drug, and the drug loading capacity and release behavior of these microspheres was valuated in vitro.Results: Spherical Ta@CaAlg microspheres with monodisperse sizes ranging from 150 to 1200 μm were fabricated by electrospraying. The results of an in vivo study showed that Ta@CaAlg microspheres possessed the qualities of both embolic agents and contrast media. They could not only feed back the real-time location and distribution of the embolic microspheres but also maintained clear X-ray imaging of embolized sites for up to 4 weeks as assessed by digital radiography and computed tomography. Digital subtraction angiography showed that they had an excellent embolic effect. Ta@CaAlg microspheres could be loaded with Dox to form "3-in-1" embolic microspheres. The maximum Dox loading was 97.3 mg Dox per mL beads and loaded microspheres exhibited pH-dependent release profiles. Conclusion: The X-ray opacity and drug-loading capability of Ta@CaAlg microspheres offers great promise in direct, real-time, in vivo investigation for TACE and long-term non-invasive re-examination.

Zeolite-loaded alginate-chitosan hydrogel beads as a topical hemostat

Hemorrhage is the leading cause of preventable death after a traumatic injury, and the largest contributor to loss of productive years of life. Hemostatic agents accelerate hemostasis and help control hemorrhage by concentrating coagulation factors, acting as procoagulants and/or interacting with erythrocytes and platelets. Hydrogel composites offer a platform for targeting both mechanical and biological hemostatic mechanisms. The goal of this work was to develop hydrogel particles composed of chitosan, alginate, and zeolite, and to assess their potential to promote blood coagulation via multiple mechanisms: erythrocyte adhesion, factor concentration, and the ability to serve as a mechanical barrier to blood loss. Several particle compositions were synthesized and characterized. Hydrogel bead composition was optimized to achieve the highest swelling capacity, greatest erythrocyte adhesion, and minimal in vitro cytotoxicity. These results suggest a polymer hydrogel-aluminosilicate composite material may serve as a platform for an effective hemostatic agent that incorporates multiple mechanisms of action. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1662-1671, 2018.

Controlled and Sequential Delivery of Fluorophores from 3D Printed Alginate-PLGA Tubes

Controlled drug delivery systems, that include sequential and/or sustained drug delivery, have been utilized to enhance the therapeutic effects of many current drugs by effectively delivering drugs in a time-dependent and repeatable manner. In this study, with the aid of 3D printing technology, a novel drug delivery device was fabricated and tested to evaluate sequential delivery functionality. With an alginate shell and a poly(lactic-co-glycolic acid) (PLGA) core, the fabricated tubes displayed sequential release of distinct fluorescent dyes and showed no cytotoxicity when incubated with the human embryonic kidney (HEK293) cell line or bone marrow stromal stem cells (BMSC). The controlled differential release of drugs or proteins through such a delivery system has the potential to be used in a wide variety of biomedical applications from treating cancer to regenerative medicine.

Formulation and Coating of Alginate and Alginate-Hydroxypropylcellulose Pellets Containing Ranolazine

The formulation and the coating composition of biopolymeric pellets containing ranolazine were studied to improve their technological and biopharmaceutical properties. Eudragit L100 (EU L100) and Eudragit L30 D-55-coated alginate and alginate-hydroxypropylcellulose (HPC) pellets were prepared by ionotropic gelation using 3 concentrations of HPC (0.50%, 0.65%, and 1.00% wt/wt) and applying different percentages (5%, 10%, 20%, and 30% wt/wt) of coating material. The uncoated pellets were regular in shape and had mean diameter between 1490 and 1570 μm. The rate and the entity of the swelling process were affected by the polymeric composition: increasing the HPC concentration, the structure of the pellets became more compact and slowed down the penetration of fluids. Coated alginate-HPC formulations were able to control the drug release at neutral pH: a higher quantity of HPC in the system determined a slower release of the drug. The nature of the coating polymer and the coating level applied affected the drug release in acidic environment: EU L100 gave better performance than Eudragit L30 D-55 and the best coating level was 20%. The pellets containing 0.65% of HPC and coated with 20% EU L100 represented the best formulation, able to limit the drug release in acidic environment and to control it at pH 6.8.

Electrosynthesis of magnetoresponsive microrobot for targeted drug delivery using calcium alginate

Targeted drug delivery systems deliver drugs precisely to a specific targeted site inside the body, and can also release the drugs with controlled kinetics to prolong the efficacy of single dose administration. The advantageous properties of hydrogels make them attractive for use in the area of drug delivery. Calcium alginate is a pH sensitive hydrogel stable in acidic media and soluble in basic media. This enables the hydrogel to absorb and release aqueous solutions at certain ranges of pH values. By absorbing an aqueous solution containing a drug, an active drug release can be triggered at a specified range of pH value. In this paper, we combined calcium alginate with cobalt nickel (CoNi) in a cylindrical hybrid micro robot by electrodeposition. The designed microrobot can be wirelessly actuated with an external magnetic manipulation system and, hence, targeted to a specific location in the human body. At this specific location, characterized by its pH range, the absorbed drug will be released. Here, the fabrication steps of the specified microrobot are characterized, namely the production of a template on a silicon chip and the subsequent template-assisted electrodeposition of CoNi and alginate. Additionally, the dynamics of drug release of calcium alginate is studied.

Dual-Cross-Linked Methacrylated Alginate Sub-Microspheres for Intracellular Chemotherapeutic Delivery

Intracellular delivery vehicles comprised of methacrylated alginate (Alg-MA) were developed for the internalization and release of doxorubicin hydrochloride (DOX). Alg-MA was synthesized via an anhydrous reaction, and a mixture of Alg-MA and DOX was formed into sub-microspheres using a water/oil emulsion. Covalently cross-linked sub-microspheres were formed via exposure to green light, in order to investigate effects of cross-linking on drug release and cell internalization, compared to traditional techniques, such as ultraviolet (UV) light irradiation. Cross-linking was performed using light exposure alone or in combination with ionic cross-linking using calcium chloride (CaCl2). Alg-MA sub-microsphere diameters were between 88 and 617 nm, and ζ-potentials were between -20 and -37 mV. Using human lung epithelial carcinoma cells (A549) as a model, cellular internalization was confirmed using flow cytometry; different sub-microsphere formulations varied the efficiency of internalization, with UV-cross-linked sub-microspheres achieving the highest internalization percentages. While blank (nonloaded) Alg-MA submicrospheres were noncytotoxic to A549 cells, DOX-loaded sub-microspheres significantly reduced mitochondrial activity after 5 days of culture. Photo-cross-linked Alg-MA sub-microspheres may be a potential chemotherapeutic delivery system for cancer treatment.

An HPLC method for microanalysis and pharmacokinetics of marine sulfated polysaccharide PSS-loaded poly lactic-co-glycolic acid (PLGA) nanoparticles in rat plasma

This study was aimed at developing a sensitive and selective HPLC method with postcolumn fluorescence derivatization for the detection of propylene glycol alginate sodium sulfate (PSS) in rat plasma. Plasma samples were prepared by a simple and fast ultrafiltration method. PSS was extracted from rat plasma with D-glucuronic acid as internal standard. Isocratic chromatographic separation was performed on a TSKgel G2500 PWxL column with the mobile phase of 0.1 M sodium sulfate at a flow rate of 0.5 mL/min. Analyte detection was achieved by fluorescence detection (FLD) at 250 nm (excitation) and 435 nm (emission) using guanidine hydrochloride as postcolumn derivatizing reagent in an alkaline medium at 120 °C. The calibration curve was linear over a concentration range of 1-500 μg/mL, and the lower limit of detection (LLOD) was found to be 250 ng/mL. This validated method was applied successfully to the pharmacokinetic study of PSS and PSS-loaded poly lactic-co-glycolic acid (PLGA) nanoparticles (PSS-NP) in rat plasma after a single intravenous (PSS only) and oral administration (PSS and PSS-NP). Significant differences in the main pharmacokinetic parameters of PSS and PSS-NP were observed. The relative bioavailability of PSS-NP was 190.10% compared with PSS which shows that PSS-NP can improve oral bioavailability.

3D hybrid wound devices for spatiotemporally controlled release kinetics

This paper presents localized and temporal control of release kinetics over 3-dimensional (3D) hybrid wound devices to improve wound-healing process. Imaging study is performed to extract wound bed geometry in 3D. Non-Uniform Rational B-Splines (NURBS) based surface lofting is applied to generate functionally graded regions. Diffusion-based release kinetics model is developed to predict time-based release of loaded modifiers for functionally graded regions. Multi-chamber single nozzle solid freeform dispensing system is used to fabricate wound devices with controlled dispensing concentration. Spatiotemporal control of biological modifiers thus enables a way to achieve target delivery to improve wound healing.

[Antihypertensive effect and pharmacokinetics of low molecular mass potassium alginate]

OBJECTIVE

To investigate the effect of low molecular weight potassium alginate (L-PA) on blood pressures in spontaneously hypertensive rats (SHRs) and its pharmacokinetics characteristics in mice.

METHODS

The systolic blood pressure (SBP) was measured by tail-cuff method in conscious SHRs. Forty rats were randomly assigned to the following five groups: control, hydrochlorothiazide (HCT, 6.25 mg/kg), L-PA in low, middle or high dose groups (100, 250, 500 mg/kg). SHRs were intragastrically (i. g.) administrated once daily for 28 days. The SBP was measured once weekly during drug treatment, and 3 and 6 days after drug with drawal. KM mice were i. g. administered with 100 mg/kg (74 MBq/kg) of 3H-L-PA. Ten microl blood samples were obtained from the tail vein at 2, 5, 10, 20, 30 min and 1, 2, 4, 6, 12, 24, 48, 72, 96, 120 or 144 h after drug administration for measuring radioactivities. Pharmacokinetics parameters of the oral administration of L-PA were analysed with DAS 2.0 software.

RESULTS

Twenty-one or 28 days after administration, the rats in the groups treated with HCT or L-PA at 100, 250 or 500 mg/kg had a significant decrease in SBP (P<0.01 vs control group). Three or 6 days after drug withdrawal, the antihypertensive effect of HCT disappeared (P>0.05), whereas the rats treated with 250 or 500 mg/kg L-PA still had lower SBP than the controls (P<0.01). The L-PA at a dose of 100 mg/kg also led to a significant decrease in SBP 3 days after drug withdrawal (P<0.05). The pharmacokinetics of L-PA (i. g.) was consistent with a two-compartment model, with 2.76 h of absorption half-life (t1/2, Ka), 42. 30 h of distributional half-life (t1/2alpha), 42. 31 h of elimination half-life (t1/2beta), and 36.28 h of terminal phase elimination half-life (t1/2z).

CONCLUSION

Oral administration of L-PA has significant anti-hypertensive effect, which can be maintained to 6 days after drug withdrawal. The sustaining anti-hypertensive effect of L-PA is probably associated with its slow elimination in vivo.

Enhanced Delivery of Bifidobacteria and Fecal Changes after Multiple Oral Administrations of Bifidobacteria-loaded Alginate Poly-l-lysine Microparticles in Human Volunteers

Enhanced delivery of bifidobacteria and fecal changes were compared following multiple oral administrations of protected bifidobacteria-loaded alginate poly-l-lysine microparticles (bap-microparticles) and unprotected bifidobacteria cultures over a period of 1 month to healthy human volunteers as preliminary in vivo studies. When bap-microparticles were orally administered, enhanced delivery of bifidobacteria was achieved. The viability of the bifidobacteria was significantly increased approximately 11.5-30 times (1.06-1.48 log cycles) during the ingestion period when compared with the bifidobacteria culture group (p < 0.05). However, other gut microflora such as bifidobacteria, enterobacteriaceae, lactic acid bacteria, and staphylococci in feces were not significantly different between the two groups. Encapsulated bifidobacteria resulted in more frequent defecation and decreased fecal viscosity.

In-vivo evaluation in rats of colon-specific microspheres containing 5-fluorouracil

The aims of this investigation were to determine the distribution in the gastrointestinal (GI) tract of Eudragit S-100 encapsulated colon-specific sodium alginate microspheres containing 5-fluorouracil (5-FU) in rats, and to perform pharmacokinetic and pharmacodynamic studies. Comparisons were with a control immediate-release (IR) formulation of 5-FU. 5-FU was distributed predominantly in the upper GI tract from the IR formulation but was distributed primarily to the lower part of the GI tract from the microsphere formulation. No drug was released in the stomach and intestinal regions from the colon-specific microspheres. Significantly, a high concentration of the active drug was achieved in colonic tissues from the colon-specific microspheres (P < 0.001), which was higher than the IC50 required to halt the growth of and/or kill colon cancer cells. Colon cancer was induced in rats by subcutaneous injection of 1,2-dimethylhydrazine (40 mg kg (-1)) for 10 weeks. The tumours induced were non-invasive adenocarcinomas and were in Duke's stage A. The 5-FU formulations were administered for 4 weeks after tumour induction. Non-significant reductions in tumour volume and multiplicity were observed in animals given the colon-specific microspheres. Enhanced levels of liver enzymes (SGOT, SGPT and alkaline phosphatase) were found in animals given the IR formulation of 5-FU, and values differed significantly (P < 0.001) from those in animals treated with the colon-specific microspheres. Elevated levels of serum albumin and creatinine, and leucocytopenia and thrombocytopenia were observed in the animals given the IR formulation. In summary, Eudragit S-100 coated alginate microspheres delivered 5-FU to colonic tissues, with reduced systemic side-effects. A long-term dosing study is required to ascertain the therapeutic benefits.

Alginate and chitosan particles as drug delivery system for cell therapy

Drug-carrying microstructures which have a size similar to biological structures are very attractive to encapsulate drugs and protect them during the transit in the human body. This paper describes polymeric (alginate and chitosan) particles (average radius 500 nm) produced by homogenization techniques. In vitro studies performed on cell lines demonstrate the effectiveness of such particles for intracellular drug delivery. Our experiments suggest that cellular up - take increases linearly with particle concentration in the growth medium, and the internalization process has a first order kinetics (characteristic time around 0.5 h(-1)). In addition, the particles degrade within 24 h from the up-take without side effects for cell viability.

3D culture of bone-derived cells immobilised in alginate following light-triggered gelation

Photoreactive liposomes have been exploited as a means of developing 3D tissue constructs. Liposomes formulated using the photosensitive lipid 1,2-bis(4-(n-butyl)phenylazo-4'-phenylbutyroyl)phosphatidylcholine (Bis Azo PC), which undergoes conformational change on stimulation with long wavelength ultraviolet light, were prepared with entrapped CaCl(2) before being incorporated into a 4% alginate solution. It was shown that stimulation of the photosensitive lipid using a light emitting diode (LED) (peak emission at 385 nm, dose equivalent to 9 mJ/cm(2)) caused the release of liposome-entrapped CaCl(2), resulting in cross-linking of the alginate solution and immobilisation of bone-derived cells over a range of seeding densities, approximately 97% of which remained viable for periods of up to 14 days in culture. Entrapment volumes of a variety of liposome types were evaluated and interdigitating fusion vesicles were identified as having the highest payload (24%), however the inclusion of cholesterol as a means of shifting Bis Azo PC sensitivity into the visible light wavelengths resulted in an approximately 10-fold reduction in calcium entrapment. This application of light-sensitised liposomes offers the potential to create complex tissue engineering substrates containing cells immobilised in precise locations, in contrast with substrates onto which cells are seeded post-production.

Preparation of superoxide dismutase loaded chitosan microspheres: Characterization and release studies

Superoxide dismutase (SOD) is the most potent antioxidant enzyme. In this study, SOD was encapsulated in chitosan microspheres to obtain suitable sustained protein delivery. Protein-loaded chitosan microspheres with various formulations were prepared based on complex coacervation process. Due to the inherent characteristic of SOD, high encapsulation efficiency could not be obtained with simple preparation method. The pH of chitosan solution is 3.0; when the chitosan microspheres were prepared with this solution, encapsulation was low. Therefore, several strategies have been tested to increase the encapsulation efficiency and good results have been obtained. 70-80% protein encapsulation efficiency was obtained. The addition of PEG to the protein solution enhanced the encapsulation efficiency also. Mean sizes of microspheres were between 1.38 and 1.94 microm. Factors affecting the release behaviour of SOD from microspheres have been studied. They included pH values of chitosan solution (the pH of chitosan solution is 3.0), addition of PEG to the protein solution and the use of adsorption technique. In general, biphasic release profiles were obtained with these formulations. The protein activity changed between 70 and 100% during the release. In general, the protein activity remained in acceptable limits. The SOD encapsulated chitosan microspheres can be prepared by changing the pH or addition of PEG, allowing the safe incorporation of protein for controlled release.

[The dynamic study of retinoic acid and its alginate sodium microspheres in rabbit eye]

OBJECTIVE

To obtain a intravitreous delay release system by injection of biodegradable polymers (alginate sodium-retinoic acid microspheres, AGS-RA microspheres) to the rabbit vitreous and study the release character of RA delivery system in vitro.

METHODS

RA was mixed with 1.5% alginate sodium and microspheres was made by a special electrostatic generator after dissolved in organic solvent; The content of AGS-RA in the microspheres and its release from the microspheres were measured by spectrophotometer. The characteristic of the metabolic dynamics of AGS-RA in the microspheres was analyzed by HPLC.

RESULTS

The size of microspheres we manufacture is (95.2443 +/- 8.6265) microm; Medicine contain quantity of RA is (1.7644 +/- 0.0453) microg/mg; Vitro test show that RA in the microspheres is release evenly in the 28 days of observation; Inject medicine to vitreous cavity show no poisonous side effect; The medicine dynamics research of microspheres showed that medicine is being even in 6 weeks releasing [the aqueous RA density of 1, 3 d, 1, 2, 3, 4, 5, 6 weeks is (23.79 +/- 0.15), (33.45 +/- 0.48), (19.95 +/- 0.79), (21.12 +/- 0.47), (19.65 +/- 0.35), (20.01 +/- 0.25), (18.24 +/- 0.27), (18.5 +/- 0.68) ng/ml, respectively]. Just in the 3rd day there is a release summit.

CONCLUSION

In vivo and in vitro tests show that AGS-RA microspheres can delay RA release uniformity.

Radiopaque Alginate Microcapsules for X-ray Visualization and Immunoprotection of Cellular Therapeutics

Alginate-poly-L-lysine-alginate (APA) microcapsules have been explored as vehicles for therapeutic drug and cell delivery. The permselectivity of these capsules provides a unique means of controlled drug release and immunoisolation of encapsulated cells. Immunoisolation is especially attractive as it abrogates the need for chronic immunosuppressive therapy and opens up the possibility for the delivery of numerous cell sources including xenogeneic grafts. APA microcapsules containing cellular therapeutics have proven effective in the short-term treatment of a wide range of diseases requiring enzyme or endocrine replacement therapy, including type I diabetes. If these microcapsules could be noninvasively monitored with X-ray imaging modalities (i.e., fluoroscopy, CT, and digital subtraction angiography), questions such as the ideal transplantation site, the best means of delivery, and the long-term survival of grafts could be better addressed. We have developed two novel alginate-based radiopaque microcapsule formulations containing either barium sulfate (Ba X-Caps) or bismuth sulfate (Bi X-Caps). As compared to conventional, nonradiopaque APA capsules, Ba X-Caps and Bi X-Caps containing human cadaveric islets resulted in a decrease in cellular viability of less than 5% up to 14 days after encapsulation. Both radiopaque capsules were found to be permeable to lectins < or =75 kDa, but were impermeable to lectins > or =120 kDa, thus ensuring the blockage of the penetration of antibodies while allowing free diffusion of insulin and nutrients. The glucose-responsive insulin secretion of the radiopaque encapsulated human islets was found to be unaltered compared to that of unlabeled controls, with human C-peptide levels ranging from 3.21 to 2.87 (Ba X-Caps) and 3.23 to 2.87 (Bi X-Caps) ng/islet at 7 and 14 days postencapsulation, respectively. Using fluoroscopy, both Ba X-Caps and Bi X-Caps could be readily visualized as single radiopaque entities in vitro. Furthermore, following transplantation in vivo in mice and rabbits, single capsules could be identified with no significant change in contrast for at least 2 weeks. This study represents the first attempt at making radiopaque microcapsules for X-ray guided delivery and imaging of cellular therapeutics. While human cadaveric islets were used as a proof-of-principle, these radiopaque capsules may have wide ranging therapeutic applications for a variety of cell types.

Alginate nanoparticles as antituberculosis drug carriers: formulation development, pharmacokinetics and therapeutic potential

BACKGROUND

Reduction in the dosing frequency of antituberculosis drugs (ATDs) by applying drug delivery technology has the potential to improve the patient compliance in tuberculosis (TB). Alginate (a natural polymer) based nanoparticulate delivery system was developed for frontline ATDs (rifampicin, isoniazid, pyrazinamide and ethambutol).

METHODS

Alginate nanoparticles were prepared by the controlled cation induced gelification method and administered orally to mice. The drug levels were analysed by high performance liquid chromatography (HPLC) in plasma/tissues. The therapeutic efficacy was evaluated in M. tuberculosis H37Rv infected mice.

RESULTS

High drug encapsulation efficiency was achieved in alginate nanoparticles, ranging from 70%-90%. A single oral dose resulted in therapeutic drug concentrations in the plasma for 7-11 days and in the organs (lungs, liver and spleen) for 15 days. In comparison to free drugs (which were cleared from plasma/organs within 12-24 h), there was a significant enhancement in the relative bioavailability of encapsulated drugs. In TB-infected mice three oral doses of the formulation spaced 15 days apart resulted in complete bacterial clearance from the organs, compared to 45 conventional doses of orally administered free drugs.

CONCLUSIONS

Alginate nanoparticles appear to have the potential for intermittent therapy of TB.

Influence of high-M alginate on the growth and survival of Atlantic cod (Gadus morhua L.) and spotted wolffish (Anarhichas minor Olafsen) fry

Atlantic cod and spotted wolffish fry were fed high-M alginate containing feed for 59 and 55 days, respectively. During this period the fry showed a higher specific growth rate compared to controls. Uptake and distribution of alginate was studied by inclusion of the (125)I-labelled molecule in the feed. The stomach and intestine contained the highest amount while the kidney, liver and spleen contained some, indicating that the alginate was taken up by the gut and transported to internal organs. Cod fry fed 0.06% and 0.1% high-M alginate showed a death rate of 51.4% and 53.3%, respectively. The lowest mortality, 48.1%, was found in fry fed 0.01% high-M alginate. Controls showed a mortality rate of 49.0%. Differences were, however, not statistically significant. Challenge of the immunostimulated fry (fed 0.02% and 0.06% alginate for 62 days) with atypical Aeromonas salmonicida bacteria resulted in accumulated mortalities of 56% and 49%, respectively, 47 days after infection. The group that received 0.06% alginate for a shorter period (47 days) and then control feed until challenged, and the group that received alginate by bath reached a cumulative mortality of 59% and 60%, respectively. Lowest mortality (44%) was seen in the control group. Numerous microabscesses were found in both immunostimulated and control fish in secondary lamellae of the gills, haematopoietic tissues of the kidneys, the submucosa and mucosa of the intestine, the spleen, the liver and the myocardium of the heart.

Intraperitoneal stability of alginate-polyornithine microcapsules in rats: an FTIR and SEM analysis

Alginate-polycation microcapsule systems have been used over decades as delivery vehicles for cell and protein therapy. These systems have been unpredictable across a range of indications with questions resulting around the inherent stability of the alginate polysaccharide and failure mode of the delivery system. The current study focuses on such a system using 5 different alginates, 2 of which are commercially purified, which are crosslinked by polyornithine. Capsules formed by frequency-generated droplet formation were studied in the peritoneal cavity of Long-Evans rats over the course of 3 months by morphometry, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy of the surface. Individual capsule components were also investigated on FTIR and a relative stability index was generated by titration for comparison to explanted samples over time. Using these techniques, a distinct degradation pattern was noted and is compared between the 5 alginate sources.

Mechanisms of formation and disintegration of alginate beads obtained by prilling

In this paper, compendial sodium alginate beads have been manufactured by laminar jet break-up technology. The effect of polymer concentration, viscosity and polymeric solution flow rate on the characteristics of beads was studied. Size distribution of alginate beads in the hydrated state was strongly dependent on the flow rate and viscosity of polymer solutions, since a transition from laminar jet break-up conditions to vibration-assisted dripping was observed. The re-hydration kinetics of dried beads in simulated gastric fluid (SGF) showed that the maximum swelling of beads was reached after 1-2 h, with an increase in volume of two to three times and a time lag dependent on the polymer concentration. The re-hydration swelling profiles in simulated intestinal fluid (SIF) showed no time lag and higher swelling volume; moreover, in this medium after the maximum swelling was reached, the bead structure was quickly disaggregated because of the presence in the medium of phosphate able to capture calcium ions present in the alginate gel structure.

Molecular interaction in alginate beads reinforced with sodium starch glycolate or magnesium aluminum silicate, and their physical characteristics

Diclofenac calcium-alginate (DCA) beads were reinforced with different amounts of sodium starch glycolate (SSG) or magnesium aluminum silicate (MAS) and were prepared using ionotropic gelation method. Complex formation of sodium alginate (SA) and SSG or MAS in calcium-alginate beads was revealed using FTIR spectroscopy. Differential scanning calorimetric study indicated that diclofenac sodium (DS) in amorphous form was dispersed in the matrix of DCA beads. The thermal behavior of SSG-DCA and MAS-DCA beads was similar to the control bead. Both additives can improve the entrapment efficiency of DCA beads. The swelling and water uptake of the beads depended on the properties of incorporated additives. The SSG-DCA beads showed a higher water uptake and swelling than MAS-DCA beads. Moreover, the swelling of the beads showed a good correlation with the square root of time. The release kinetic of the beads in pH 6.8 phosphate buffer was swelling controlled mechanism, while that in distilled water followed Higuchi's model. The slower release rate and the longer lag time in pH 6.8 phosphate buffer was obtained from the SSG-DCA and MAS-DCA beads because of complex formation between SA and SSG or MAS. However, SSG in the beads could increase the release of DS from the beads in distilled water because it acted as a channeling agent. In contrast, MAS retarded the release of DS from the beads in distilled water due to the stronger matrix formation.

Effect of formulation and process variables on the release behavior of amoxicillin matrix tablets

The sustained release of amoxicillin is desired to be confined to the upper gastrointestinal tract to treat certain kind of infections. In vitro dissolution, at pH 1.2, of amoxicillin sustained release tablets has been studied varying the proportion of Carbopol 971P NF and sodium alginate as well as the ethanol/water proportion in the granulation fluid. M(t), the amount of drug released at time (t) and defined in terms of the total drug released over a long time period (M(inf), was described by M(t)/M(inf) = kt(n). Matrices with increasing proportions of sodium alginate showed increasing values of the exponent indicative of the release mechanism (n) and increasing release constant values (k). This is attributed to a drop in the coherence of the polymeric matrix with increasing alginate proportions that produces an increasing polymer relaxation and erosion. Decreasing Carbopol 971P NF proportions reduce the amount of dissolved polymer during granulation, producing a lesser obstruction of amoxicillin dissolution. Alginate proportions of 80% produce near zero order release profiles. Granules obtained with increasing ethanol proportions showed increasing release constant values and a minor change in the exponent (n) values. This is considered a result of lower polymer dissolution during granulation that allows a lesser matrix coherence and a greater amoxicillin dissolution. Alginate matrices granulated with different ethanol/water proportions showed no significant changes in the amoxicillin release profile. There is a trend toward increasing floating times with increasing Carbopol 971P NF proportions.

Coating alginate microspheres with a serum albumin-alginate membrane: application to the encapsulation of a peptide

Calcium alginate gel microspheres coated with a human serum albumin (HSA)-alginate membrane were prepared adapting a transacylation method previously applied to large beads. The procedure involved emulsification of an aqueous solution of sodium alginate and propylene glycol alginate (PGA) in an oily phase, followed by addition of CaCl(2). The resulting gel microspheres were transferred in an aqueous solution of HSA. The addition of 0.5 M NaOH started the reaction between PGA and HSA, producing amide bonds and forming a membrane around the particles. An optimization study was conducted, notably exploring the addition of HSA to the internal phase. The microcapsules were studied with respect to morphology (optical and scanning electron microscopy) and size (laser granulometry), in comparison with uncoated gel microspheres. Biocompatibility was checked in osteoblast cultures. Lysine-arginine-phenylalanine-lysine (KRFK) was encapsulated and the release kinetics was studied in vitro. The method provided stable microspheres (size around 60 microm), with a membrane surviving a treatment with citrate and resisting lyophilization. The microcapsules were shown biocompatible. The release of KRFK was slower (release time>8 days) than that of uncoated microspheres. These microcapsules might be useful as peptide containers to be combined with prosthetic materials for improving osteointegration.

Chitosan-alginate multilayer beads for controlled release of ampicillin

The aim of this study is to develop multilayer beads with improved properties for controlled delivery of the antibiotic ampicillin. Ionotropic gelation was applied to prepare single and multilayer beads using various combinations of chitosan and Ca(2+) as cationic components and alginate and polyphosphate as anions. Beads prepared with higher concentrations of chitosan entrapped more ampicillin. During incubation in simulated gastric fluid, the beads swelled and started to float but did not show any sign of erosion. Single layer chitosan-alginate beads released 70% of the drug within 4 h. Multilayer beads released only 20-30% in the same period of time. During subsequent incubation in simulated intestinal fluid, both single and multilayer beads continued to release drug. At least part of this release is due to disintegration of the beads. The rate of release both in gastric and intestinal fluid and the kinetics of disintegration in intestinal fluid can be controlled by changing the chitosan concentration in the coagulation fluid. The release of the drug can also be controlled by the degree of cross-linking using polyphosphate. Cross-linked multilayer beads were prepared that released only 40% of the entrapped drug during 24 h. It is concluded that chitosan-alginate multilayer beads, cross-linked with polyphosphate offer an opportunity for controlled gastrointestinal passage of compounds with low molecular weight like ampicillin.

Multifunctional Drug Delivery System Using Starch-Alginate Beads for Controlled Release

Utilizing starch-containing alginate beads, a novel drug delivery system (DDS) was developed. With the starch inside, the composite bead could be dried in its original bead shape and handled in the dried state. By employing alginate multi-coating strategy on the starch-alginate beads, detained or controlled release was efficiently achieved and successfully demonstrated for a model peptide drug, L-phenylalanine. The initial latent time and release rate of the drug inside the beads were able to be controlled simply by varying the number of multi-coatings. While the latent time for the initial release was negligible for non-coated starch-alginate beads, the latent times of beads coated one, two, and four times increased to 15, 30, and 70 min, respectively. Furthermore, the alginate component of the composite beads could adsorb and remove heavy metals such as lead from the body. These multifunctional beads combined with the novel coating process will greatly benefit alginate gel-based DDS.

Oesophageal bioadhesion of sodium alginate suspensions

Sodium alginate suspensions in a range of water miscible vehicles were investigated as novel bioadhesive liquids for targeting the oesophageal mucosa. Such a dosage form might be utilised to coat the oesophageal surface and provide a protective barrier against gastric reflux, or to deliver therapeutic agents site-specifically. Alginate suspensions swelled and formed an adherent viscous layer on contact with the mucosa. The swelling kinetics of alginate particles on the oesophageal surface was examined with respect to vehicle composition and related to the extent, duration and location of bioadhesion within the oesophagus. Mucosal retention was evaluated in two in vitro models utilising tissue immersion and a peristaltic tube. By varying the vehicle composition it was possible to modulate the rate of swelling of alginate particles on the mucosa and the mucosal retention of suspensions. Suspensions containing predominantly glycerol exhibited superior retention and were preferentially retained within the lower oesophagus. The propensity of these suspensions to rapidly swell on the mucosa and establish adhesive/cohesive bonds may explain their enhanced retention. The potential to control, through vehicle composition, the extent, duration and location of oesophageal retention could provide a useful tool for site targeting of viscous polymers to the oesophagus.

[Some interactions of natural and synthetic anionic polymers with biologically active substances]

Anionic polymers are nowadays extensively used in drug form technology, especially in drug delivery and drug targeting. Development of proper drug and macromolecular excipient composition allows controlled drug delivery in the term of the drug concentration in blood or other tissues, and in the term of the action-time. Between anionic polymers most frequently carbopols, eudragits, alginates and pectins are used. Application of anionic polymers in drug form technology is an up to date problem. According to new synthesis methods and new anionic polymers, new drug delivery systems would be researched. Most selective and safe devices should be developed, concerning biodegradation aspects.

Optimization of pH-independent release of nicardipine hydrochloride extended-release matrix tablets using response surface methodology

The purpose of this study was to optimize the pH-dependent release of nicardipine hydrochloride extended release formulations by using simultaneously combination two hydrophilic polymers: hydroxypropylmethylcellulose (HPMC) and sodium alginate as retardant and avicel as additive. The constrained mixture experimental design was used to prepare systematic model formulations which were composed of three formulation variables: the content of HPMC (X1), avicel (X2), and sodium alginate (X3). The response surface methodology (RSM) and multiple response optimization utilizing the polynomial equation were used to search for the optimal formulation with specific release rate at different time intervals and to quantify the effect of each formulation variables. The drug release percent at 3, 6 and 12 h were the target responses and were restricted to 10-30% (Y3h), 40-65% (Y6h) and not less than 80% (Y12h), respectively. The results showed that the effect of combination of HPMC and sodium alginate was the most influence factor on the drug release from extended-release matrix tablets. The observed results of Y3h, Y6h and Y12h coincided well with the predictions in the RSM optimization technique, indicating it was quite useful for optimizing pharmaceutical formulation. The mechanism of drug release from extended-release matrix tablets was dependent on the added amount of alginate. The release kinetic of drug from HPMC matrix tablets with alginate was followed the zero-order release pattern.

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.

In situ cross-linking of sodium alginate with calcium and aluminum ions to sustain the release of theophylline from polymeric matrices

Small matrices of calcium alginate or aluminium alginate have been investigated as possible controlled release systems for drugs. The objective of the present study was to sustain the release of theophylline from alginate matrices using different concentrations of aluminium chloride and calcium chloride in presence and absence of HPMC. Tablets containing differing concentrations of aluminium and calcium chloride were produced and the release rate of theophylline was tested using the basket dissolution apparatus over 8 h. Increasing amounts of aluminium chloride from 0.0001 to 0.00068 moles decreased the release of theophylline from 95.1 +/- 0.27 to 29.5 +/- 1.5, indicating a significant effect of aluminium ions on a reduction in the release rate of theophylline from sodium alginate matrices. In the case of matrices containing different concentrations of calcium ions, as the concentration of calcium chloride increased, the release rate increased to an optimum then declined after this. This was due to insufficient calcium ions being available to cross-link with the sodium alginate to form an insoluble gel. The effect of aluminium ions, as this is a trivalent ion compared to calcium, which is a divalent ion, aluminium ions are able to decrease the release rate with a smaller concentration compared to calcium ions. The results also showed that the presence of HPMC caused a reduction in release rate of theophylline from alginate matrices containing calcium chloride. Whereas, in the case of alginate matrices containing aluminium chloride the release rate of theophylline increased in presence of HPMC. For comparing the dissolution data, dissolution efficiency (DE) was used. The values of DE are consistent with the dissolution data. The results show that within a formulation series, DE values generally decrease when the cation concentration increases and this criterion can be used to describe the effect of calcium and aluminium ions on the release behaviour of theophylline from polymeric matrices.

N4-alkyloxycarbonyl derivatives of cytosine: physicochemical characterisation, and cytosine regeneration rates and release from alginic acid gels

Nucleobase containing compounds might constitute a potential alternative to conventional antibiotics in the treatment of Helicobacter pylori infections. N4-alkyloxycarbonyl-cytosine derivatives were synthesized and subjected to basic physicochemical characterisation including assessment of hydrolytic stability in various matrices. pH-rate profiles of selected compounds (range 0-12) were constructed. Hydrolysis of the derivatives in slightly alkaline solution (60 degrees C) resulted in quantitative conversion to parent cytosine whereas at acidic pH (60 degrees C) liberation of cytosine was in most cases accompanied by the parallel formation of uracil. Interestingly the lipophilic N4-adamantyloxycarbonyl-cytosine prodrug exhibited a half-life of 41 min (pH 1.1 at 37 degrees C) with quantitative conversion to parent cytosine, the degradation rate being approximately 200 times faster than that of the non-cyclic aliphatic derivatives investigated. The presence of pig stomach homogenates, pepsin A and H. pylori did not have a noteworthy catalytic effect on the hydrolysis of the derivatives. The release of parent cytosine was markedly delayed from alginic acid gels loaded with the acid-labile and poorly soluble ADC prodrug as compared to gels loaded with parent cytosine.

Cross-linked alginate–gelatine beads: a new matrix for controlled release of pindolol

This work is focused on the development of a new particulate drug delivery system using a sodium alginate matrix containing pindolol as a model drug molecule for intestinal drug prolonged release. Calcium alginate beads are known to be unable to control the release of most insoluble drugs. Pindolol-loaded alginate-gelatine beads have been developed using a solvent-free technique that involves a cross-linking reaction. Modifications in matrix structure and physicochemical behaviour caused by the cross-linking reaction were assessed during particle formation and drug release. Several parameters, such as matrix gelling rate, encapsulation efficiency, drug release profile and matrix erosion rate, were investigated. Physicochemical characterisation indicates the formation of a new alginate-gelatine matrix and shows that pindolol does not interfere with the matrix formation process. Matrix swelling of calcium alginate beads induced by phosphate buffer ends up in erosion and destruction. However, for cross-linked beads swelling does not lead to complete erosion, which may be the main cause of pindolol retention within the matrix. The modifications introduced in the initial calcium alginate formulation by means of an appropriate method such as the use of a cross-linking agent successfully changed the matrix performance, allowing the controlled release of pindolol.

Effective removal of alginate-poly-L-lysine microcapsules from pancreatic islets by use of trypsin-EDTA

Although the transplantation of alginate-poly-L-lysine-alginate encapsulated islets of Langerhans usually is successful, graft survival is still limited. Molecular analysis by RT-PCR of the encapsulated islets may provide insight into the mechanisms that affect islets during graft failure. However, RT-PCR on encapsulated islets is not possible because the poly-L-lysine of the capsule interferes with both cDNA synthesis and PCR amplification. We applied a method that mechanically removes the microcapsules from the islets after a short trypsin-EDTA treatment (decapsulation), thereby enabling RT-PCR analysis. The results of this study show that the decapsulation procedure does not affect islet vitality and has only minor effects on islet function and morphology. The decapsulation does not affect GAPDH, beta-actin, Bcl-2, or Bax gene expression. This method is an improvement over the time-consuming manual dissection of microcapsules because it allows for the rapid and relatively harmless removal of capsules on a larger scale. Decapsulation offers the possibility of applying RT-PCR, as well as other methods, which cannot be performed on encapsulated islets.

Chemotherapeutic potential of alginate-chitosan microspheres as anti-tubercular drug carriers

OBJECTIVES

This study was designed to develop alginate-chitosan microspheres as drug carriers to reduce dose/dosing frequency in the management of tuberculosis (TB), which otherwise demands prolonged chemotherapy.

METHODS

Alginate-chitosan microspheres encapsulating three frontline anti-tuberculous drugs (ATDs), rifampicin, isoniazid and pyrazinamide, were formulated. A therapeutic dose and a half-therapeutic dose of the microsphere-encapsulated ATDs were orally administered to guinea pigs for pharmacokinetic/chemotherapeutic evaluations, respectively.

RESULTS

The drug encapsulation efficiency ranged from 65% to 85% with a loading of 220-280 mg of drug per gram microspheres. Administration of a single oral dose of the microspheres to guinea pigs resulted in sustained drug levels in the plasma for 7 days and in the organs for 9 days. The half-life and mean residence time of the drugs were increased 13- to 15-fold by microsphere encapsulation, along with an enhanced relative/absolute bioavailability. The sustained release and increase in bioavailability were also observed with a sub-therapeutic dose of the microspheres. In Mycobacterium tuberculosis H37Rv-infected guinea pigs, administration of a therapeutic dose of microspheres spaced 10 days apart produced a clearance of bacilli equivalent to conventional treatment for 6 weeks. The most important observation, however, was the documentation of therapeutic benefit with a half-therapeutic dose of the microspheres administered weekly.

CONCLUSION

Alginate-chitosan microspheres hold promise as a potential natural polymer-based oral ATD carrier for better management of TB.

Biodegradation of naphthalene by free and alginate entrapped Pseudomonas sp

Naphthalene degradation by freely suspended and immobilized cells of Pseudomonas sp. isolated from contaminated effluents has been investigated in batch cultures and continuously in a packed bed reactor. Naphthalene concentration was varied from 25 mM to 75 mM, the temperature (30 degrees C) and pH (7.0) were kept constant. The results showed good acclimation of the strain to carbon source and degradation rate was highly affected by initial concentration. Alginate-entrapped cells have given good yields although initial rates were not as high as those encountered with free cells. A first order exponential decay kinetic model was proposed with values of parameters for each initial concentration. A laboratory scale packed-bed bioreactor was designed using parameters calculated above and continuous experiments were realized at different flow rates (100 to 200 ml/h), with different feed concentrations and operating during 30 days. The conversion at low feed concentrations and low flow rates was complete whereas at high flow rates and high concentrations it was less efficient because of diffusional limitations and short residence time.

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.

Oral colon-specific drug delivery for bee venom peptide: development of a coated calcium alginate gel beads-entrapped liposome

Colon-specific drug delivery systems (CDDSs) can be used to improve the bioavailability of protein and peptide drugs through the oral route. A novel formulation for oral administration using coated calcium alginate gel beads-entrapped liposome and bee venom peptide as a model drug has been investigated for colon-specific drug delivery in vitro. Drug release studies under conditions mimicking stomach to colon transit have shown that the drug was protected from being released completely in the physiological environment of the stomach and small intestine. The release rate of bee venom from the coated calcium alginate gel beads-entrapped liposome was dependent on the concentration of calcium and sodium alginate, the amount of bee venom in the liposome, as well as the coating. Furthermore, a human gamma-scintigraphy technique was used in vivo to determine drug delivery more precisely. The colonic arrival time of the tablets was found to be 4-5 h. The results clearly demonstrated that the coated calcium alginate gel beads-entrapped liposome is a potential system for colon-specific drug delivery.

Numerical modelling of insulin and amyloglucosidase release from swelling Ca-alginate beads

The release of insulin hexamer (39 kD) and amyloglucosidase (AMG, 97 kD), entrapped in spherical Ca-alginate beads, was investigated. While the release of insulin could be described solely by diffusion this was not the case for the 1.6 (rm/rm) larger AMG protein, where rm is the Stokes-Einstein effective molecular radius. Because the alginate bead size was not constant during the release experiments, it was hypothesised that in addition to the diffusional mass transfer, a non-negligible convective flow of liquid in or out of the beads was present due to swelling or shrinkage, respectively. Although it should be expected that the effective diffusion coefficient of AMG is only slightly lower than that of insulin, the results show that the effective diffusions coefficient of AMG was found to be much smaller. In the case of AMG, it was shown that including bead size changes and the resulting convective flow in the numerical model, release could be described more accurately. The numerical model was able to describe the release characteristics from both shrinking, swelling, and non-swelling alginate beads. To evaluate the effect of bead swelling on the protein release rate, a swelling modulus and a release index was defined, describing the different effects on release of smaller and larger proteins.

Effects of physical-chemical characteristics on the sorption of selected endocrine disruptors by dissolved organic matter surrogates

Sorption coefficients (K(oc) values) of selected endocrine disruptors for a wide variety of dissolved organic matter (DOM) were measured using fluorescence quenching and solubility enhancement. 17beta-Estradiol, estriol, 17alpha-ethynylestradiol, p-nonylphenol, p-tert-octylphenol, and dibutylphthalate were selected as endocrine disruptors. Aldrich humic acid, Suwannee River humic and fulvic acids, Nordic fulvic acid, alginic acid, dextran, and tannic acid were selected as DOM surrogates. The resulting sorption coefficients (log K(oc)) were independent of octanol-water partitioning coefficients (log K(ow)) of the selected endocrine disruptors, indicating the hydrophobic interaction is not the predominant sorption mechanism. Moreover, the K(oc) values for the selected endocrine disruptors, especially the steroid estrogens, correlated much better with UV absorptivity at 272 nm (A272) and phenolic group concentration of the DOM than with either the H/O or the (O+N)/C atomic ratio of the DOM. This suggests that the sorption mechanism is closely related to the interaction between pi-electrons and the hydrogen bonds, i.e., the affinity between phenolic groups of the steroid estrogens and DOM is suggested to provide a relatively large contribution to the overall sorption and yield the K(oc) values of the steroid estrogens as high as those of the alkylphenols and dibutylphthalate, which are suggested to be dominated by nonspecific hydrophobic interaction.

Preparation and release characteristics of polymer-coated and blended alginate microspheres

To prevent a rapid drug release from alginate microspheres in simulated intestinal media, alginate microspheres were coated or blended with polymers. Three polymers were selected and evaluated such as HPMC, Eudragit RS 30D and chitosan, as both coating materials and additive polymers for controlling the drug release. This study focused on the release characteristics of polymer-coated and blended alginate microspheres, varying the type of polymer and its concentration. The alginate microspheres were prepared by dropping the mixture of drug and sodium alginate into CaCl(2) solution using a spray-gun. Polymer-coated microspheres were prepared by adding alginate microspheres into polymer solution with mild stirring. Polymer-blended microspheres were prepared by dropping the mixture of drug, sodium alginate and additive polymer with plasticizer into CaCl(2) solution. In vitro release test was carried out to investigate the release profiles in 500 ml of phosphate buffered saline (PBS, pH 7.4). As the amount of polymer in sodium alginate or coating solution increase, the drug release generally decreased. HPMC-blended microspheres swelled but withstood the disintegration, showing an ideal linear release profiles. Chitosan-coated microspheres showed smooth and round surface and extended the release of drug. In comparison with chitosan-coated microspheres, HPMC-blended alginate microspheres can be easily made and used for controlled drug delivery systems due to convenient process and controlled drug release.

Alginate-diltiazem hydrochloride beads: optimization of formulation factors, in vitro and in vivo availability

Alginate beads containing diltiazem hydrochloride (DTZ) were prepared by the ionotropic gelation method. The effects of various factors (alginate concentration, additives type, calcium chloride concentration and curing time) on the efficiency of drug loading were investigated. The formulation containing a mixture of 0.8% methylcellulose (MC) and 4% alginate cured in 2% calcium chloride for 6 h was chosen as the best formula regarding the loading efficiency. The release rate of DTZ from various beads formulations was investigated. The release of drug from alginate beads followed two mechanisms; by diffusion and relaxation of the polymer at pH 1.2, whilst diffusion and erosion are at pH 6.8. The in vitro release of DTZ from MC-alginate beads showed an extended release pattern which was compared with that from commercially available sustained-release (Dilzem SR) and fast release tablets (Dilzem). Thermal analysis revealed that the drug was molecularly dispersed in the beads matrix. Although the release characteristics of DTZ from Dilzem SR and MC-alginate beads were completely different, the bioavailability of DTZ in dogs was comparable as measured by AUC, MRT and relative bioavailability. The absolute bioavailability of MC-alginate beads and Dilzem SR was 88 and 93%, respectively.

Method for monitoring alginate released in biological fluids by high-performance anion-exchange chromatography with pulsed amperometric detection

The use of alginate-entrapped cells in cell therapy requires a method for monitoring possible released compound within biological fluids following either their implantation or inoculation in artificial organs. Oligomannuronic and oligoguluronic acids were prepared by enzymatic depolymerization with alginate lyase from Pseudomonas alginovora, characterized by high-performance anion-exchange chromatography with pulsed amperometric detection and quantitated in human, pig and rabbit blood, urine and tissue samples. The method was tested for linearity and detection limit, accuracy, intra- and inter-day precision. The limit of detection was 3 microgram/ml in both urine and plasma and 5 mg/g of tissues. The relative standard deviations (RSDs) of intra-day precision were 6.0-16.6% and 4.8-8.7% in plasma and urine, respectively; the RSDs of inter-day precision were 5.1-14.4% and 5.0-11.6% in plasma and urine, respectively. Thus, this method appears suitable for the measurement of released alginate from entrapped cells used in cell therapy.

Effects of natural polysaccharide addition on drug release from calcium-induced alginate gel beads

Calcium-induced alginate gel beads (Alg-Ca) containing various polysaccharides, including an alginate hydrolysate, were prepared and the drug release profiles were investigated. Hydrocortisone (HC) was gradually released from Alg-Ca into the mimic gastric fluid, while in intestinal fluid, it was quickly released with the dissolution of Alg-Ca. However, with Alg-Ca containing 5% chitin (CT), dissolution of Alg-Ca was not observed, and release of HC showed apparent zero-order kinetics. Furthermore, addition of the alginate hydrolysate altered the HC-release profile for Alg-Ca.