Calcium alginate microparticles for oral administration: II. Effect of formulation factors on drug release and drug entrapment efficiency

Alginate-Based Carriers Loaded with Mulberry (Morus alba L.) Leaf Extract: A Promising Strategy for Prolonging 1-Deoxynojirimicyn (DNJ) Systemic Activity for the Nutraceutical Management of Hyperglycemic Conditions

The iminosugar 1-deoxynojirimicyn (DNJ) contained in mulberry leaves has displayed systemic beneficial effects against disorders of carbohydrate metabolism. Nevertheless, its effect is impaired by the short half-life. Alginate-based carriers were developed to encapsulate a DNJ-rich mulberry extract: Ca-alginate beads, obtained by external gelation, and spray-dried alginate microparticles (SDMs). Mean size and distribution, morphology, drug loading, encapsulation efficiency, experimental yield, and release characteristics were determined for the two formulations. Ca-alginate beads and SDMs exhibited an encapsulation efficiency of about 54% and 98%, respectively, and a DNJ loading in the range of 0.43-0.63 μg/mg. The in vitro release study demonstrated the carriers' capability in controlling the DNJ release in acid and basic conditions (<50% in 5 h), due to electrostatic interactions, which were demonstrated by 1H-NMR relaxometry studies. Thus, alginate-based particles proved to be promising strategies for producing food supplements containing mulberry leaf extracts for the management of hyperglycemic state.

Box-Behnken design to optimize the cross-linked sodium alginate/mucilage/Aloe vera film: Physical and mechanical studies

The crosslinked sodium alginate/mucilage/Aloe vera/glycerin was optimized by different ratios of each factor to be an absorption wound dressing base for infected wound healing. Mucilage was extracted from seeds of Ocimum americanum. The Box-Behnken design (BBD) in response surface methodology (RSM) was used to construct an optimal wound dressing base with the target ranges of mechanical and physical properties of each formulation. The independent variables selected were sodium alginate (X1: 0.25-0.75 g), mucilage (X2: 0.00-0.30 g), Aloe vera (X3: 0.00-0.30 g), and glycerin (X4: 0.00-1.00 g). The dependent variables were tensile strength (Y1: low value), elongation at break (Y2: high value), Young's modulus (Y3: high value), swelling ratio (Y4: high value), erosion (Y5: low value), and moisture uptake (Y6: high value). The results showed that the wound dressing base with the most desirable response consists of sodium alginate (59.90 % w/w), mucilage (23.96 % w/w), and glycerin (16.14 % w/w) without Aloe vera gel powder (0.00 % w/w).

A Review of Factors Affecting Ganoderma Basal Stem Rot Disease Progress in Oil Palm

In recent years, oil palm has grown on a major scale as it is a prominent commodity crop that contributes the most to almost every producing country's gross domestic product (GDP). Nonetheless, existing threats such as the Ganoderma basal stem rot (BSR) disease have been deteriorating the oil palm plantations and suitable actions to overcome the issue are still being investigated. The BSR disease progression in oil palm is being studied using the disease progression through the plant disease triangle idea. This concept looks at all potential elements that could affect the transmission and development of the disease. The elements include pathogenic, with their mode of infection in each studied factor.

Impact of heterogeneously crosslinked calcium alginate networks on the encapsulation of β-carotene-loaded beads

This study investigated the impact of heterogeneity of crosslinking on a range of physical and mechanical properties of calcium alginate networks formed via external gelation with 0.25-2% sodium alginate and 2.5 and 5% CaCl₂. Crosslinking in films with 1-2% alginate was highly heterogeneous, as indicated by their lower calcium content (35-7 mg Ca·g alginate^-1) and apparent solubility (5-6%). Overall, films with 1-2% alginate showed higher resistance (tensile strength = 51-147 MPa) but lower elasticity (Elastic Modulus = 2136-10,079 MPa) than other samples more homogeneous in nature (0.5% alginate, Elastic Modulus = 1918 MPa). Beads with 0.5% alginate prevented the degradation of β-carotene 1.5 times more efficiently than 1% beads (5% CaCl₂) at any of the storage temperatures studied. Therefore, it was postulated that calcium alginate networks crosslinked to a greater extent and in a more homogeneous manner showed better mechanical performance and barrier properties for encapsulation applications.

Preparation and evaluation of an oral mucoadhesive gel containing nystatin-loaded alginate microparticles

Nystatin is an antifungal agent used for prophylaxis and treatment of candidiasis, especially oral mycosis. Efficacy of nystatin conventional dosage forms is limited by the short residence time and bitter taste of the drug. This research aims at designing an optimized formulation of oral mucoadhesive gel of nystatin-loaded alginate microparticles, which can be retained in the mouth. Sodium alginate solution containing nystatin was added to the solution of calcium chloride under stirring. Microparticles containing nystatin were incorporated into the Carbopol gel. Size, loading, and release profile and mucoadhesion were investigated. The most suitable microparticles with particle size of < 250 μm were prepared with alginate concentration of 1%(w/v), calcium chloride of 1%(w/v), drug:polymer concentration 1%, and ratio of alginate solution:calcium chloride of 1:10. This formulation showed 49.1% drug loading and 98.2% encapsulation efficiency. Carbopol 934 gel provided optimal mucoadhesive properties. Release profile proved a burst release, which can be attributed to the surface associated drug, followed by a slower sustained release phase for all microparticles. The developed system with ability to adhere to the oral mucosa has great appeal for treatment of localized infections and can mask bitter taste of the drug and be retained in the mouth for long periods.

Functionality of Food Components and Emerging Technologies

This review article introduces nutrition and functional food ingredients, explaining the widely cited terms of bioactivity, bioaccessibility, and bioavailability. The factors affecting these critical properties of food components are analyzed together with their interaction and preservation during processing. Ultimately, the effect of emerging (non-thermal) technologies on different food components (proteins, carbohydrates, lipids, minerals, vitamins, polyphenols, glucosinolates, polyphenols, aroma compounds, and enzymes) is discussed in spite of preserving their functional properties. Non-thermal technologies can maintain the bioavailability of food components, improve their functional and technological properties, and increase the recovery yields from agricultural products. However, the optimization of operational parameters is vital to avoid degradation of macromolecules and the oxidation of labile compounds.

Microencapsulation of Coenzyme Q10 and bile acids using ionic gelation vibrational jet flow technology for oral delivery

Developing new delivery dosage forms with robust delivery and safety profiles remains a challenge to the pharmaceutical industry in terms of optimum gut absorption, consistent dosing and bioavailability; particularly for orally administered drugs that are poorly water soluble. Coenzyme Q10 is an example of a poorly water-soluble compound with low bioavailability, and significant inter-individual variation after oral administration; limiting its optimum efficacy, as a powerful antioxidant with significant promise in treating hearing disorders. Microencapsulation technology is one way to optimize drug bioavailability and absorption profile. One example is Ionic Gelation Vibrational Jet Flow techniques, using new encapsulating parameters to determine the nature of formed capsules. Bile acids are an example of an excipient that can be used to improve membrane permeability; and will be examined. This review addresses the applications of microencapsulation technology on oral delivery and efficacy profiles of poorly water-soluble drugs, focusing on Coenzyme Q10.

Wurster Fluidised Bed Coating of Microparticles: Towards Scalable Production of Oral Sustained-Release Liquid Medicines for Patients with Swallowing Difficulties

Suspension of microparticles in an easy-to-swallow liquid is one approach to develop sustained-release formulations for children and patients with swallowing difficulties. However, to date production of sustained-release microparticles at the industrial scale has proven to be challenging. The aim of this investigation was to develop an innovative concept in coating sustained-release microparticles using industrial scalable Wurster fluidised bed to produce oral liquid suspensions. Microcrystalline cellulose cores (particle size <150 μm) were coated with Eudragit® NM 30 D and Eudragit® RS/RL 30 D aqueous dispersions using a fluidised bed coater. A novel approach of periodic addition of a small quantity (0.1% w/w) of dry powder glidant, magnesium stearate, to the coating chamber via an external port was applied throughout the coating process. This method significantly increased coating production yield from less than 50% to up to 99% compared to conventional coating process without the dry powder glidant. Powder rheology tests showed that dry powder glidants increased the tapped density and decreased the cohesive index of coated microparticles. Reproducible microencapsulation of a highly water-soluble drug, metoprolol succinate, was achieved, yielding coated microparticles less than 200 μm in size with 20-h sustained drug release, suitable for use in liquid suspensions. The robust, scalable technology presented in this study offers an important solution to the long-standing challenges of formulating sustained-release dosage forms suitable for children and older people with swallowing difficulties.

A Magnesium-Enriched 3D Culture System that Mimics the Bone Development Microenvironment for Vascularized Bone Regeneration

The redevelopment/regeneration pattern of amputated limbs from a blastema in salamander suggests that enhanced regeneration might be achieved by mimicking the developmental microenvironment. Inspired by the discovery that the expression of magnesium transporter-1 (MagT1), a selective magnesium (Mg) transporter, is significantly upregulated in the endochondral ossification region of mouse embryos, a Mg-enriched 3D culture system is proposed to provide an embryonic-like environment for stem cells. First, the optimum concentration of Mg ions (Mg2+) for creating the osteogenic microenvironment is screened by evaluating MagT1 expression levels, which correspond to the osteogenic differentiation capacity of stem cells. The results reveal that Mg2+ selectively activates the mitogen-activated protein kinase/extracellular regulated kinase (MAPK/ERK) pathway to stimulate osteogenic differentiation, and Mg2+ influx via MagT1 is profoundly involved in this process. Then, Mg-enriched microspheres are fabricated at the appropriate size to ensure the viability of the encapsulated cells. A series of experiments show that the Mg-enriched microenvironment not only stimulates the osteogenic differentiation of stem cells but also promotes neovascularization. Obvious vascularized bone regeneration is achieved in vivo using these Mg-enriched cell delivery vehicles. The findings suggest that biomaterials mimicking the developmental microenvironment might be promising tools to enhance tissue regeneration.

Transformable bubble-filled alginate microfibers via vertical microfluidics

A novel buoyancy-assisted vertical microfluidic setup has been developed to fabricate a new class of transformable bubble-filled hydrogel microfibers. A co-axial flow of an aqueous sodium-alginate solution enveloping an air phase was injected into a quiescent aqueous CaCl2 solution, through a vertically-oriented co-axial glass-capillary setup. This induced instantaneous gelation and produced bubble-filled calcium-alginate fibers. The surface-morphology of the resulting fibers was controlled from smooth to wavy by slowing down the gelation kinetics. The advantage of the buoyancy force acting on the fibers by the trapped air bubbles was taken not only to shape the fibers, but to transform them into several other novel hydrogel structures, such as water-filled segmented fibers, beaded microfibers, and threaded capsules. The ultimate transformability was demonstrated by the fibers being allowed to elongate and then undergo controlled destruction to produce uniform anisotropic micro-particles with a wide range of sizes and shapes from frustums to barrel and cylindrical types.

A review on the strategies for oral delivery of proteins and peptides and their clinical perspectives

In the modern world, a number of therapeutic proteins such as vaccines, antigens, and hormones are being developed utilizing different sophisticated biotechnological techniques like recombinant DNA technology and protein purification. However, the major glitches in the optimal utilization of therapeutic proteins and peptides by the oral route are their extensive hepatic first-pass metabolism, degradation in the gastrointestinal tract (presence of enzymes and pH-dependent factors), large molecular size and poor permeation. These problems can be overcome by adopting techniques such as chemical transformation of protein structures, enzyme inhibitors, mucoadhesive polymers and permeation enhancers. Being invasive, parenteral route is inconvenient for the administration of protein and peptides, several research endeavors have been undertaken to formulate a better delivery system for proteins and peptides with major emphasis on non-invasive routes such as oral, transdermal, vaginal, rectal, pulmonary and intrauterine. This review article emphasizes on the recent advancements made in the delivery of protein and peptides by a non-invasive (peroral) route into the body.

Overview of biopolymers as carriers of antiphlogistic agents for treatment of diverse ocular inflammations

Inflammation of the eye is a usual clinical condition that can implicate any part of the eye. The nomenclature of variety of such inflammations is based on the ocular part involved. These diseases may jeopardize normal functioning of the eye on progression. In general, corticosteroids, antihistamines, mast cell stabilizers and non-steroidal anti-inflammatory drugs (NSAIDs) are used to treat inflammatory diseases/disorders of the eye. There have been several attempts via different approaches of drug delivery to overcome the low ocular bioavailability resulting from shorter ocular residence time. The features like safety, ease of elimination and ability to sustain drug release have led to application of biopolymers in ocular therapeutics. Numerous polymers of natural origin such as gelatin, collagen, chitosan, albumin, hyaluronic acid, alginates etc. have been successfully employed for preparation of different ocular dosage forms. Chitosan is the most explored biopolymer amongst natural biopolymers because of its inherent characteristics. The emergence of synthetic biopolymers (like PVP, PACA, PCL, POE, polyanhydrides, PLA, PGA and PLGA) has also added new dimensions to the drug delivery strategies meant for treatment of ophthalmic inflammations. The current review is an endeavor to describe the utility of a variety of biomaterials/polymers based drug delivery systems as carrier for anti-inflammatory drugs in ophthalmic therapeutics.

Release and swelling studies of an innovative antidiabetic-bile acid microencapsulated formulation, as a novel targeted therapy for diabetes treatment

In previous studies carried out in our laboratory, a bile acid formulation exerted a hypoglycaemic effect in a rat model of type 1 diabetes (T1D). When the antidiabetic drug gliclazide was added to the bile acid, it augmented the hypoglycaemic effect. In a recent study, we designed a new formulation of gliclazide-deoxycholic acid (G-DCA), with good structural properties, excipient compatibility and which exhibited pseudoplastic-thixotropic characteristics. The aim of this study is to test the slow release and pH controlled properties of this new formulation. The aim is also to examine the effect of DCA on G release kinetics at various pH values and different temperatures. Microencapsulation was carried out using our Buchi-based microencapsulating system developed in our laboratory. Using sodium alginate (SA) polymer, both formulations were prepared including: G-SA (control) and G-DCA-SA (test) at a constant ratio (1:3:30), respectively. Microcapsules were examined for efficiency, size, release kinetics, stability and swelling studies at pH 1.5, 3, 7.4 and 7.8 and temperatures of 25 °C and 37 °C. The new formulation is further optimised by the addition of DCA. DCA reduced bead-swelling of the microcapsules at pH 7.8 and 3 at 25 °C and 37 °C, and even though bead size remains similar after DCA addition, the percentage of G release was enhanced at high pH values (pH 7.4 and 7.8, p < 0.01). The new formulation exhibits colon-targeted delivery and the addition of DCA prolonged G release suggesting its suitability for the sustained and targeted delivery of G and DCA to the lower intestine.

Stability and Release Kinetics of an Advanced Gliclazide-Cholic Acid Formulation: The Use of Artificial-Cell Microencapsulation in Slow Release Targeted Oral Delivery of Antidiabetics

Introduction

In previous studies carried out in our laboratory, a bile acid (BA) formulation exerted a hypoglycaemic effect in a rat model of type-1 diabetes (T1D). When the antidiabetic drug gliclazide (G) was added to the bile acid, it augmented the hypoglycaemic effect. In a recent study, we designed a new formulation of gliclazide-cholic acid (G-CA), with good structural properties, excipient compatibility and exhibits pseudoplastic-thixotropic characteristics. The aim of this study is to test the slow release and pH-controlled properties of this new formulation. The aim is also to examine the effect of CA on G release kinetics at various pH values and different temperatures.

Method

Microencapsulation was carried out using our Buchi-based microencapsulating system developed in our laboratory. Using sodium alginate (SA) polymer, both formulations were prepared: G-SA (control) and G-CA-SA (test) at a constant ratio (1:3:30), respectively. Microcapsules were examined for efficiency, size, release kinetics, stability and swelling studies at pH 1.5, pH 3, pH 7.4 and pH 7.8 and temperatures of 20 and 30 °C.

Results

The new formulation is further optimised by the addition of CA. CA reduced microcapsule swelling of the microcapsules at pH 7.8 and pH 3 at 30 °C and pH 3 at 20 °C, and, even though microcapsule size remains similar after CA addition, percent G release was enhanced at high pH values (pH 7.4 and pH 7.8, p < 0.01).

Conclusion

The new formulation exhibits colon-targeted delivery and the addition of CA prolonged G release suggesting its suitability for the sustained and targeted delivery of G and CA to the lower intestine.

Microencapsulation Approach for Orally Extended Delivery of Glipizide: In vitro and in vivo Evaluation

Glipizide is an effective antidiabetic agent, however, it suffers from relatively short biological half-life. To solve this encumbrance, it is a prospective candidate for fabricating glipizide extended release microcapsules. Microencapsulation of glipizde with a coat of alginate alone or in combination with chitosan or carbomer 934P was prepared employing ionotropic gelation process. The prepared microcapsules were evaluated in vitro by microscopical examination, determination of the particle size, yield and microencapsulation efficiency. The filled capsules were assessed for content uniformity and drug release characteristics. Stability study of the optimised formulas was carried out at three different temperatures over 12 weeks. In vivo bioavailability study and hypoglycemic activity of C9 microcapsules were done on albino rabbits. All formulas achieved high yield, microencapsulation efficiency and extended t_1/2. C9 and C19 microcapsules attained the most optimised results in all tests and complied with the dissolution requirements for extended release dosage forms. These two formulas were selected for stability studies. C9 exhibited longer shelf-life and hence was chosen for in vivo studies. C9 microcapsules showed an improvement in the drug bioavailability and significant hypoglycemic activity compared to immediate release tablets (Minidiab^® 5 mg). The optimised microcapsule formulation developed was found to produce extended antidiabetic activity.

Alginate-lanthanide microspheres for MRI-guided embolotherapy

In cancer therapy, a promising treatment option to accomplish a high tumor-to-normal-tissue ratio is endovascular intervention with microsized particles, such as embolotherapy. In this study, alginate microspheres (ams) were prepared with the JetCutter technique, which is based on cutting a sodium alginate solution jet stream into small droplets of uniform size which are then cross-linked with different lanthanides or iron-III, resulting in microspheres of a predefined size which can be visualized by magnetic resonance imaging (MRI). The microspheres were investigated for their size and morphology (light microscopy and scanning electron microscopy analysis), cation content and MRI properties. The lanthanide-ams formulations, with a uniform size of 250 μm and a cation content between 0.72-0.94%, showed promising results for MR imaging. This was further demonstrated for Ho(3+)-cross-linked alginate microspheres (Ho(3+)-ams), the most potent microsphere formulation with respect to MR visualization, allowing single sphere detection and detailed microsphere distribution examination. Intravascular infusion of Ho(3+)-ams by catherization of ex vivo rabbit and porcine liver tissue and assessment of the procedure with MRI clearly showed accumulation and subsequently embolization of the targeted vessels, allowing accurate monitoring of the microsphere biodistribution throughout the tissue. Therefore, the different alginate-lanthanide microsphere formulations developed in this study show great potential for utilization as image-guided embolotherapy agents.

Statistical approach for assessing the influence of calcium silicate and HPMC on the formulation of novel alfuzosin hydrochloride mucoadhesive-floating beads as gastroretentive drug delivery systems

Multiparticulate floating drug delivery systems have proven potential as controlled-release gastroretentive drug delivery systems that avoid the "all or none" gastric emptying nature of single-unit floating dosage forms. An objective of the presence investigation was to develop calcium silicate (CaSi)/calcium alginate (Ca-Alg)/hydroxypropyl methylcellulose (HPMC) mucoadhesive-floating beads that provide time- and site-specific drug release of alfuzosin hydrochloride (Alf). Beads were prepared by simultaneous internal and external gelation method utilizing 3(2) factorial design as an experimental design; with two main factors evaluated for their influence on the prepared beads; the concentration of CaSi as floating aid (X (1)) and the percentage of HPMC as viscosity enhancer and mucoadhesive polymer (X (2)), each of them was tested in three levels. Developed formulations were evaluated for yield, entrapment efficiency, particle size, surface topography, and buoyancy. Differential scanning calorimetry, Fourier transform infrared spectroscopy, in vitro drug release, as well as in vitro mucoadhesion using rat stomach mucosal membrane were also conducted. Percentage yield and entrapment efficiency ranged from 57.03% to 78.51% and from 49.78% to 83.26%, respectively. Statistical analysis using ANOVA proved that increasing the concentration of either CaSi or HPMC significantly increased the beads yield. Both CaSi and HPMC concentrations were found to significantly affect Alf release from the beads. Additionally, higher CaSi concentration significantly increased the beads diameter while HPMC concentration showed significant positive effect on the beads mucoadhesive properties. CaSi/Ca-Alg/HPMC beads represent simple floating-mucoadhesive gastroretentive system that could be useful in chronopharmacotherapy of benign prostatic hyperplasia.

Effect of experimental parameters on the formation of alginate–chitosan nanoparticles and evaluation of their potential application as DNA carrier

This study introduces a new procedure to prepare alginate-chitosan nanoparticles and examines several experimental parameters in relation to their formation and characteristics. Using DLS and TEM analysis, nanoparticle formation was shown to be predominantly affected by the ratio of alginate to chitosan, the molecular weight of the biopolymers and the solution pH. We report a method that results in spherical particles with mean diameters ranging from 323 nm to 1.6 microm, depending on the preparation conditions. The smallest particles were formed using lower molecular weight polymers with pH between 5.0 and 5.6 and having an alginate/chitosan weight ratio of 1:1.5. We have shown that DNA can be loaded with 60% association efficiency. Our system demonstrates suitable size, loading and release characteristics for application in drug- and gene-delivery systems.

Marine polysaccharides in microencapsulation and application to aquaculture: "from sea to sea"

This review's main objective is to discuss some physico-chemical features of polysaccharides as intrinsic determinants for the supramolecular structures that can efficiently provide encapsulation of drugs and other biological entities. Thus, the general characteristics of some basic polysaccharides are outlined in terms of their conformational, dynamic and thermodynamic properties. The analysis of some polysaccharide gelling properties is also provided, including the peculiarity of the charged polysaccharides. Then, the way the basic physical chemistry of polymer self-assembly is made in practice through the laboratory methods is highlighted. A description of the several literature procedures used to influence molecular interactions into the macroscopic goal of the encapsulation is given with an attempt at classification. Finally, a practical case study of specific interest, the use of marine polysaccharide matrices for encapsulation of vaccines in aquaculture, is reported.

Alginate graft copolymers and alginate-co-excipient physical mixture in oral drug delivery

OBJECTIVES

Use of alginate graft copolymers in oral drug delivery reduces dosage form manufacture complexity with reference to mixing or coating processes. It is deemed to give constant or approximately steady weight ratio of alginate to covalently attached co-excipient in copolymers, thereby leading to controllable matrix processing and drug release. This review describes various grafting approaches and their outcome on oral drug release behaviour of alginate graft copolymeric matrices. It examines drug release modulation mechanism of alginate graft copolymers against that of co-excipients in non-grafted formulations.

KEY FINDINGS

Drug release from alginate matrices can be modulated through using either co-excipients or graft copolymers via changing their swelling, erosion, hydrophobicity/hydrophilicity, porosity and/or drug adsorption capacity. However, it is not known if the drug delivery performance of formulations prepared using alginate graft copolymers is superior to those incorporating graft-equivalent co-excipient physically in a dosage form without grafting but at the corresponding graft weight, owing to limited studies being available.

CONCLUSIONS

The value of alginate graft copolymers as the potential alternative to alginate-co-excipient physical mixture in oral drug delivery cannot be entirely defined by past and present research. Such an issue is complicated by the lack of green chemistry graft copolymer synthesis approach, high grafting process cost, complications and hazards, and the formed graft copolymers having unknown toxicity. Future research will need to address these matters to achieve a widespread commercialization and industrial application of alginate graft copolymers in oral drug delivery.

Novel antigen delivery technologies: a review

Over the past few years, new insights into immunobiology and delivery systems have allowed the development of better vaccines and for a wider range of diseases. Currently available vaccines represent outstanding success story in modern medicine and have had a dramatic effect on morbidity and mortality worldwide. Conventional vaccines have been based on live attenuated, or killed, viruses or bacteria, or recombinant proteins from these organisms. The design of live attenuated vaccines depended to some extent on serendipity and resulted in low success rates. Both live attenuated and killed vaccines require handling of live pathogens and are associated with safety problems. Despite the success of vaccines, there is a clear need for novel antigen delivery technologies to improve vaccine efficacy and safety. Antigen stability, safety, and immunogenicity are the key hurdles in development of novel antigen delivery technologies. Nowadays, various novel drug delivery systems are becoming one of the fastest growing sectors in the pharmaceutical and biotechnological industries. Delivery of vaccines via oral, intranasal, transcutaneous, and intradermal routes will decrease the risk of needle-borne diseases and may eliminate the need for trained personnel and sterile equipment. Currently, various techniques involving DNA vaccines, adjuvants, nanoparticles, liposome, microneedle, and NanoMAP technology are being developed and evaluated. This review focuses on the current development of some novel vaccine delivery systems and will explore the non-parenteral routes of vaccine administrations.

Preparation and characterization of nanoparticles based on hydrophobic alginate derivative as carriers for sustained release of vitamin D3

Hydrophobic alginate derivative was prepared by modification of alginate by acid chloride reaction using oleoyl chloride without organic solvents. The conjugate of oleoyl alginate ester (OAE) was confirmed by FT-IR and (1)H NMR. The degree of substitution (DS) of OAE was determined by (1)H NMR, and it ranged from 0.84 to 3.85. In distilled water, OAE formed self-assembled nanoparticles at low concentrations in aqueous medium, and nanoparticles retained their structural integrity both in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). The loading and release characteristics of nanoparticles based on OAE were investigated using vitamin D(3) as a model nutraceutical. As the concentration of vitamin D(3) increased, the loading capacity (LC) increased, whereas the loading efficiency (LE) decreased. Nanoparticles could release vitamin D(3) at a sustained rate in gastrointestinal fluid. These results revealed the potential of OAE nanoparticles as oral carriers for sustained release of vitamin D(3).

Formulation and characterization of the microencapsulated entomopathogenic fungus Metarhizium anisopliae MA126

Bioinsecticides are expected to be used for controlling major species of aphids. The present study explored a liquid phase coating technique for the formulation of microencapsulated conidia of the entomopathogenic fungus Metarhizium anisopliae MA126. Various parameters for microencapsulation were investigated. The biopolymers sodium alginate, hydroxypropyl methyl cellulose (HPMC) and chitosan were tested as coating materials. Calcium chloride was used as the cross-linking agent for converting soluble sodium alginate into an insoluble form. To improve the efficiency of microencapsulation, the additives of HPMC, dextrin, chitosan or HPMC/chitosan in various ratios (1 : 1, 1 : 3 and 3 : 1) were used as the coating materials. The particle size of a bare microcapsule was less than 30 microm. Larger size microcapsules were produced using vortex method by comparison with that using homogenization method. The latter method, however, was easy to scale up. The effect of coating materials on the morphology and encapsulation efficiency of the microcapsules was also studied. The best encapsulation efficiency (78%) was using HPMC as the additive of the coating material. The next was dextrin (70%). By measuring the germination rate, the results showed that the activity was approximately 80% of the initial after 6 months of storage at 4 degrees C, while that of the bare conidia was less than 50% stored in identical conditions.

Effects of microwave on drug-release responses of spray-dried alginate microspheres

CONTEXT

Microspheres prepared from rigid guluronic acid- (MG) and flexible mannuronic acid-rich (MC) alginate will undergo different drug release changes with respect to the influence of microwave on the matrix. An in-depth understanding of their differences in drug release changes is attainable through investigating cross-linking agent-free alginate microspheres prepared by spray-drying technique.

OBJECTIVE

The behavior of MG and MC alginate in controlling drug release responses of spray-dried microspheres against microwave was investigated. Sodium diclofenac was used as a model water-soluble drug. The formed microspheres were subjected to drug release, drug content, size, shape, surface morphology, Fourier transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffractometry analysis.

RESULTS

MC microspheres required a shorter period of microwave irradiation to reduce drug release extent than MG microspheres. In response to microwave, the drug release profiles of 1:1 MG-MC microspheres resembled MC microspheres.

DISCUSSION

The state of polymer-polymer and drug-polymer interaction via O-H and/or N-H moiety of microspheres was affected by alginate chain flexibility under the influence of microwave. It then governed the drug release responses of microspheres.

CONCLUSION

The drug release property of alginate microspheres can be modified by microwave irradiation, and its changes are a function of alginate conformation.

Synthesis of multilayered alginate microcapsules for the sustained release of fibroblast growth factor-1

Alginate microcapsules coated with a permselective poly-L-ornithine (PLO) membrane have been investigated for the encapsulation and transplantation of islets as a treatment for type 1 diabetes. The therapeutic potential of this approach could be improved through local stimulation of microvascular networks to meet mass transport demands of the encapsulated cells. Fibroblast growth factor-1 (FGF-1) is a potent angiogenic factor with optimal effect occurring when it is delivered in a sustained manner. In this article, a technique is described for the generation of multilayered alginate microcapsules with an outer alginate layer that can be used for the delivery of FGF-1. The influence of alginate concentration and composition (high mannuronic acid (M) or guluronic acid (G) content) on outer layer size and stability, protein encapsulation efficiency, and release kinetics was investigated. The technique results in a stable outer layer of alginate with a mean thickness between 113 and 164 μm, increasing with alginate concentration and G-content. The outer layer was able to encapsulate and release FGF-1 for up to 30 days, with 1.25% of high G alginate displaying the most sustained release. The released FGF-1 retained its biologic activity in the presence of heparin, and the addition of the outer layer did not alter the permselectivity of the PLO coat. This technique could be used to generate encapsulation systems that deliver proteins to stimulate local neovascularization around encapsulated islets.

Design of in situ dispersible and calcium cross-linked alginate pellets as intestinal-specific drug carrier by melt pelletization technique

Conventional alginate pellets underwent rapid drug dissolution and loss of multiparticulate characteristics such as aggregation in acidic medium, thereby promoting oral dose dumping. This study aimed to design sustained-release dispersible alginate pellets through rapid in situ matrix dispersion and cross-linking by calcium salts during dissolution. Pellets made of alginate and calcium salts were prepared using a solvent-free melt pelletization technique that prevented reaction between processing materials during agglomeration and allowed such a reaction to occur only in dissolution phase. Drug release was remarkably retarded in acidic medium when pellets were formulated with water-soluble calcium acetate instead of acid-soluble calcium carbonate. Different from calcium salt-free and calcium carbonate-loaded matrices that aggregated or underwent gradual erosion, rapid in situ solvation of calcium acetate in pellets during dissolution resulted in burst of gas bubbles, fast pellet breakup, and dispersion. The dispersed fragments, though exhibiting a larger specific surface area for drug dissolution than intact matrix, were rapidly cross-linked by Ca(2+) from calcium acetate and had drug release retarded till a change in medium pH from 1.2 to 6.8. Being dispersible and pH-dependent in drug dissolution, these pellets are useful as multiparticulate intestinal-specific drug carrier without exhibiting dose dumping tendency of a "single-unit-like" system via pellet aggregation.

Oral insulin

Oral insulin is an exciting area of research and development in the field of diabetology. This brief review covers the various approaches used in the development of oral insulin, and highlights some of the recent data related to novel oral insulin preparation.

Bile salt-reinforced alginate-chitosan beads

A polymeric delayed release protein delivery system was investigated with albumin as the model drug. The polysaccharide chitosan was reacted with sodium alginate in the presence of calcium chloride to form beads with a polyelectrolyte. In this study, attempts were made to extend albumin release in the phosphate buffer at pH 6.8 from the alginate-chitosan beads by reinforcing the matrix with bile salts. Sodium taurocholate was able to prevent albumin release at pH 1.2, protecting the protein from the acidic environment and extending the total albumin release at pH 6.8. This effect was explained by an interaction between the permanent negatively charged sulfonic acid of sodium taurocholate with the amino groups of chitosan. Mild formulation conditions, high bovine serum albumin (BSA) entrapment efficiency, and resistance to gastrointestinal release seem to be synergic and promising factors toward the development of an oral protein delivery form.