Alginate–chitosan systems: In vitro controlled release of triamcinolone and in vivo gastrointestinal transit

Orthogonal Gelations to Synthesize Core-Shell Hydrogels Loaded with Nanoemulsion-Templated Drug Nanoparticles for Versatile Oral Drug Delivery

Hydrophobic active pharmaceutical ingredients (APIs) are ubiquitous in the drug development pipeline, but their poor bioavailability often prevents their translation into drug products. Industrial processes to formulate hydrophobic APIs are expensive, difficult to optimize, and not flexible enough to incorporate customizable drug release profiles into drug products. Here, a novel, dual-responsive gelation process that exploits orthogonal thermo-responsive and ion-responsive gelations is introduced. This one-step "dual gelation" synthesizes core-shell (methylcellulose-alginate) hydrogel particles and encapsulates drug-laden nanoemulsions in the hydrogel matrices. In situ crystallization templates drug nanocrystals inside the polymeric core, while a kinetically stable amorphous solid dispersion is templated in the shell. Drug release is explored as a function of particle geometry, and programmable release is demonstrated for various therapeutic applications including delayed pulsatile release and sequential release of a model fixed-dose combination drug product of ibuprofen and fenofibrate. Independent control over drug loading between the shell and the core is demonstrated. This formulation approach is shown to be a flexible process to develop drug products with biocompatible materials, facile synthesis, and precise drug release performance. This work suggests and applies a novel method to leverage orthogonal gel chemistries to generate functional core-shell hydrogel particles.

Novel Zinc/Silver Ions-Loaded Alginate/Chitosan Microparticles Antifungal Activity against Botrytis cinerea

Addressing the growing need for environmentally friendly fungicides in agriculture, this study explored the potential of biopolymer microparticles loaded with metal ions as a novel approach to combat fungal pathogens. Novel alginate microspheres and chitosan/alginate microcapsules loaded with zinc or with zinc and silver ions were prepared and characterized (microparticle size, morphology, topography, encapsulation efficiency, loading capacity, and swelling behavior). Investigation of molecular interactions in microparticles using FTIR-ATR spectroscopy exhibited complex interactions between all constituents. Fitting to the simple Korsmeyer-Peppas empirical model revealed the rate-controlling mechanism of metal ions release from microparticles is Fickian diffusion. Lower values of the release constant k imply a slower release rate of Zn2+ or Ag+ ions from microcapsules compared to that of microspheres. The antimicrobial potential of the new formulations against the fungus Botrytis cinerea was evaluated. When subjected to tests against the fungus, microspheres exhibited superior antifungal activity especially those loaded with both zinc and silver ions, reducing fungal growth up to 98.9% and altering the hyphal structures. Due to the slower release of metal ions, the microcapsule formulations seem suitable for plant protection throughout the growing season. The results showed the potential of these novel microparticles as powerful fungicides in agriculture.

Alginate-based drug carrier systems to target inflammatory bowel disease: A review

Inflammatory bowel disease (IBD) is an inflammatory disorder that affects the gastrointestinal tract. IBD has become an increasingly common condition in both developed and developing nations over the last few decades, owing to a variety of factors like a rising population and diets packed with processed and junk foods. While the root pathophysiology of IBD is unknown, treatments are focused on medications aimed to mitigate symptoms. Alginate (AG), a marine-derived polysaccharide, is extensively studied for its biocompatibility, pH sensitivity, and crosslinking nature. This polymer is thoroughly researched in drug delivery systems for IBD treatment, as it is naturally available, non-toxic, cost effective, and can be easily and safely cross-linked with other polymers to form an interconnected network, which helps in controlling the release of drugs over an extended period. There are various types of drug delivery systems developed from AG to deliver therapeutic agents; among them, nanotechnology-based systems and hydrogels are popular due to their ability to facilitate targeted drug delivery, reduce dosage, and increase the therapeutic efficiency. AG-based carrier systems are not only used for the sustained release of drug, but also used in the delivery of siRNA, interleukins, and stem cells for site directed drug delivery and tissue regenerating ability respectively. This review is focussed on pathogenesis and currently studied medications for IBD, AG-based drug delivery systems and their properties for the alleviation of IBD. Moreover, future challenges are also be discoursed to improve the research of AG in the field of biopharmaceuticals and drug delivery.

Polyphenol Release and Antioxidant Activity of the Encapsulated Antioxidant Crude Extract from Cold Brew Spent Coffee Grounds under Simulated Food Processes and an In Vitro Static Gastrointestinal Model

An ionic gelation technique based on an alginate-calcium-based encapsulation process was prepared as the delivery matrix for antioxidant crude extracts from cold brew spent coffee grounds (350 mg/mL). All the encapsulated samples were treated with different simulated food processes, namely pH 3, pH 7, low-temperature long-time (LTLT) pasteurization, and high-temperature short-time (HTST) pasteurization, to evaluate the stability of the encapsulated matrices. The results showed that alginate (2%, w/v)/maltodextrin (2%, w/v) (CM), and alginate (2%, w/v)/inulin (5%, w/v) (CI) could enhance encapsulation efficiency (89.76 and 85.78%, respectively) and provide lower swelling behavior after being treated using the simulated food processes. Both CM and CI could control the release of antioxidants during the gastric phase (2.28-3.98 and 2.52-4.00%, respectively) and gradual release in the intestinal phase (6.80-11.78 and 4.16-12.72%, respectively) compared to pure alginate (CA). In addition, pasteurization treatment at pH 7.0 produced the highest accumulated release of total phenolic content (TPC) and antioxidant activity (DPPH) after digestion in the in vitro gastrointestinal system compared to the other simulated food processes. The thermal process resulted in a greater release of compounds from the encapsulated matrix during the gastric phase. On the other hand, the treatment with pH 3.0 resulted in the lowest accumulated release of TPC and DPPH (5.08 and 5.12%, respectively), which indicated phytochemical protection.

Sodium Alginate—Natural Microencapsulation Material of Polymeric Microparticles

From the multitude of materials currently available on the market that can be used in the development of microparticles, sodium alginate has become one of the most studied natural anionic polymers that can be included in controlled-release pharmaceutical systems alongside other polymers due to its low cost, low toxicity, biocompatibility, biodegradability and gelatinous die-forming capacity in the presence of Ca²⁺ ions. In this review, we have shown that through coacervation, the particulate systems for the dispensing of drugs consisting of natural polymers are nontoxic, allowing the repeated administration of medicinal substances and the protection of better the medicinal substances from degradation, which can increase the capture capacity of the drug and extend its release from the pharmaceutical form.

Nanocarriers for Active Ingredients of Chinese Medicine (AIFCM) Used in Gastrointestinal Cancer Therapy

Active ingredients of Chinese medicine (AIFCM) are pharmacological substances taken from traditional Chinese medicine that show promise in treating gastrointestinal cancer. Compared with traditional chemotherapeutic drugs, AIFCM have advantages such as multi-target and multi-level treatment of gastrointestinal cancer. Nanocarriers have the following advantages, better bioavailability, passive or active targeting of tumor sites and responsive release of drugs. The use of nanocarriers for delivery of AIFCM in treatment of gastrointestinal cancer, can overcome the disadvantages of some AIFCM, such as insolubility and low bioavailability. In this review, we first outline the background on gastrointestinal cancer, main curative factors and conventional therapeutic approaches. Then, the mechanisms for AIFCM in gastrointestinal cancer therapy are presented in the following four aspects: gene regulation, immune modulation, cellular pathway transduction, and alteration of intestinal flora. Thirdly, preparation of various nanocarriers and results when combining AIFCM in gastrointestinal cancer are presented. Fourth, application of novel targeted nanocarriers and responsive nanocarriers in gastrointestinal tumors is further introduced. Finally, the application of AIFCM in the treatment of gastrointestinal cancer is summarized and prospected, hoping to shed some light on the nanocarrier-bound AIFCM in the treatment of gastrointestinal cancer.

Alginate-based nanocarriers for the delivery and controlled-release of bioactive compounds

Alginate-based nanocarriers are propitious vehicles used for the delivery of bioactive compounds (bioactives). In this area, calcium alginate and sodium alginate are the most promising wall materials because they are nontoxic, comparatively cheap, simple in production, biocompatible and biodegradable. In this review, we have highlighted different alginate-based nanocarriers such as nanoparticles, nanofibers, nanoemulsions, nanocomplexes, and nanohydrogels; also entrapment of different bioactives within alginate nanocarriers and their bioavailability in the gastric environment has been comprehensively discussed. Being biopolymers, alginates can be exploited as emulsifiers/ encapsulants for entrapment and delivery of different bioactives such as vitamins, minerals, essential fatty acids, peptides, essential oils, bioactive oils, polyphenols and carotenoids. Furthermore, the use of alginate-based nanocarriers in combination with other polysaccharides/ emulsifiers was recognized as the most effective and favorable approach for the protection, delivery and sustained release of bioactives.

Budding Multi-matrix Technology-a Retrospective Approach, Deep Insights, and Future Perspectives

The human race is consistently striving for achieving good health and eliminate disease-causing factors. For the last few decades, scientists have been endeavoring to invent and innovate technologies that can substitute the conventional dosage forms and enable targeted and prolonged drug release at a particular site. The novel multi-matrix technology is a type of matrix formulation where the formulation is embraced to have a matrix system with multiple number of matrices. The MMX technology embraces with a combination of outer hydrophilic layer and amphiphilic/lipophilic core layer, within which drug is encapsulated followed by enteric coating for extended/targeted release at the required site. In comparison to conventional oral drug delivery systems and other drug delivery systems, multi-matrix (MMX) technology formulations afford many advantages. Additionally, it attributes for targeting strategy aimed at the colon and offers modified prolonged drug release. Thus, it has emerged rapidly as a potential alternative option in targeted oral drug delivery. However, the development of this MMX technology formulations is a exigent task and also has its own set of limitations. Due to its promising advantages and colon targeting strategy over the other colon targeted drug delivery systems, premier global companies are exploiting its potential. This article review deep insights into the formulation procedures, drug delivery mechanism, advantages, limitations, safety and efficacy studies of various marketed drug formulations of MMX technology including regulatory perspectives and future perspectives.

Electro-hydrodynamic assisted synthesis of lecithin-stabilized peppermint oil-loaded alginate microbeads for intestinal drug delivery

Peppermint oil (PO) is the most prominent oil using in pharmaceutical formulations with its significant therapeutic value. In this sense, this oil is attracting considerable attention from the scientific community due to its traditional therapeutic claim, biological and pharmacological potential in recent research. An organic solvent-free and environment-friendly electrohydrodynamic assisted (EHDA) technique was employed to prepared PO-loaded alginate microbeads. The current study deals with the development, optimization, in vitro characterization, in vivo gastrointestinal tract drug distribution and ex-vivo mucoadhesive properties, antioxidant, and anti-inflammatory effects of PO-loaded alginate microbeads. The optimization results indicated the voltage and flow rate have a significant influence on microbeads size and sphericity factor and encapsulation efficiency. All these optimized microbeads showed a better drug release profile in simulated intestinal fluid (pH 6.8) at 2 h. However, a minor release was found in acidic media (pH 1.2) at 2 h. The optimized formulation showed excellent mucoadhesive properties in ex-vivo and good swelling characterization in intestine media. The microbeads were found to be well distributed in various parts of the intestine in in vivo study. PO-loaded alginate microbeads similarly showed potential antioxidant effects with drug release. The formulation exhibited possible improvement of irritable bowel syndrome (IBS) in MO-induced rats. It significantly suppressed proinflammatory cytokines, i.e., interleukin- IL-1β, and upregulated anti-inflammatory cytokine expression, i.e., IL-10. It would be a promising approach for targeted drug release after oral administration and could be considered an anti-inflammatory therapeutic strategy for treating IBS.

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

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

Recent Development of Alginate-Based Materials and Their Versatile Functions in Biomedicine, Flexible Electronics, and Environmental Uses

Alginate is a natural polysaccharide that is easily chemically modified or compounded with other components for various types of functionalities. The alginate derivatives are appealing not only because they are biocompatible so that they can be used in biomedicine or tissue engineering but also because of the prospering bioelectronics that require various biomaterials to interface between human tissues and electronics or to serve as electronic components themselves. The study of alginate-based materials, especially hydrogels, have repeatedly found new frontiers over recent years. In this Review, we document the basic properties of alginate, their chemical modification strategies, and the recent development of alginate-based functional composite materials. The newly thrived functions such as ionically conductive hydrogel or 3D or 4D cell culturing matrix are emphasized among other appealing potential applications. We expect that the documentation of relevant information will stimulate scientific efforts to further develop biocompatible electronics or smart materials and to help the research domain better address the medicine, energy, and environmental challenges faced by human societies.

Biomedical Applications of Bacteria-Derived Polymers

Plastics have found widespread use in the fields of cosmetic, engineering, and medical sciences due to their wide-ranging mechanical and physical properties, as well as suitability in biomedical applications. However, in the light of the environmental cost of further upscaling current methods of synthesizing many plastics, work has recently focused on the manufacture of these polymers using biological methods (often bacterial fermentation), which brings with them the advantages of both low temperature synthesis and a reduced reliance on potentially toxic and non-eco-friendly compounds. This can be seen as a boon in the biomaterials industry, where there is a need for highly bespoke, biocompatible, processable polymers with unique biological properties, for the regeneration and replacement of a large number of tissue types, following disease. However, barriers still remain to the mass-production of some of these polymers, necessitating new research. This review attempts a critical analysis of the contemporary literature concerning the use of a number of bacteria-derived polymers in the context of biomedical applications, including the biosynthetic pathways and organisms involved, as well as the challenges surrounding their mass production. This review will also consider the unique properties of these bacteria-derived polymers, contributing to bioactivity, including antibacterial properties, oxygen permittivity, and properties pertaining to cell adhesion, proliferation, and differentiation. Finally, the review will select notable examples in literature to indicate future directions, should the aforementioned barriers be addressed, as well as improvements to current bacterial fermentation methods that could help to address these barriers.

Encapsulation of Synthesized Plant Growth Regulator Based on Copper(II) Complex in Chitosan/Alginate Microcapsules

A new copper complex, trans-diaqua-trans-bis [1-hydroxy-1,2-di (methoxycarbonyl) ethenato] copper (abbreviation Cu(II) complex), was synthesized and its plant growth regulation properties were investigated. The results show a sharp dependence of growth regulation activity of the Cu(II) complex on the type of culture and its concentration. New plant growth regulator accelerated the development of the corn root system (the increase in both length and weight) but showed a smaller effect on the development of the wheat and barley root systems. Stimulation of corn growth decreased with increasing Cu(II) complex concentration from 0.0001% to 0.01% (inhibition at high concentrations-0.01%). The development of corn stems was also accelerated but to a lesser extent. Chitosan-coated calcium alginate microcapsules suitable for delivery of Cu(II) complex to plants were prepared and characterized. Analysis of the FTIR spectrum showed that complex molecular interactions between functional groups of microcapsule constituents include mainly electrostatic interactions and hydrogen bonds. Microcapsules surface exhibits a soft granular surface structure with substructures consisting of abundant smaller particles with reduced surface roughness. Release profile analysis showed Fickian diffusion is the rate-controlling mechanism of Cu(II) complex releasing. The obtained results give new insights into the complexity of the interaction between the Cu(II) complex and microcapsule formulation constituents, which can be of great help in accelerating product development for the application in agriculture.

Technologies and Formulation Design of Polysaccharide-Based Hydrogels for Drug Delivery

Polysaccharide-based hydrogel particles (PbHPs) are very promising carriers aiming to control and target the release of drugs with different physico-chemical properties. Such delivery systems can offer benefits through the proper encapsulation of many drugs (non-steroidal and steroidal anti-inflammatory drugs, antibiotics, etc) ensuring their proper release and targeting. This review discusses the different phases involved in the production of PbHPs in pharmaceutical technology, such as droplet formation (SOL phase), sol-gel transition of the droplets (GEL phase) and drying, as well as the different methods available for droplet production with a special focus on prilling technique. In addition, an overview of the various droplet gelation methods with particular emphasis on ionic cross-linking of several polysaccharides enabling the formation of particles with inner highly porous network or nanofibrillar structure is given. Moreover, a detailed survey of the different inner texture, in xerogels, cryogels or aerogels, each with specific arrangement and properties, which can be obtained with different drying methods, is presented. Various case studies are reported to highlight the most appropriate application of such systems in pharmaceutical field. We also describe the challenges to be faced for the breakthrough towards clinic studies and, finally, the market, focusing on the useful approach of safety-by-design (SbD).

The impact of a hygroscopic chitosan coating on the controlled release behaviour of zinc hydroxide nitrate–sodium dodecylsulphate–imidacloprid nanocomposites

The hydrophilic and hygroscopic nature of chitosan creates gel layer that slowed the ion exchange process between intercalated imidacloprid and incoming anion.

Influence of surface morphology and structure of alginate microparticles on the bioactive agents release behavior

The structure-property relationship in alginate microparticles (microspheres and microcapsules prepared with or without Trichoderma viride spores (Tv) was investigated. Surface morphology, structure and release behavior from alginate microparticles strongly depend on calcium concentration and presence of Tv and chitosan layer. All microparticles exhibited a granular surface structure with substructures consisting of abundant smaller particles. In vitro active agents release study revealed that the increase in calcium cation concentration reduced the release rate of Tv (˜84% for microspheres; ˜57% for microcapsules) and calcium cations (˜20% for microspheres; ˜23% for microcapsules). The average decrease in k values due to chitosan layer addition is 41% for Tv and 93% for calcium ions, respectively. The underlying Tv release mechanism from microspheres is anomalous transport kinetics, whereas from microcapsules is controlled by Type II transport. The differences in microparticle surface properties did not affect the mechanism controlling calcium ions release detected as diffusion through microparticles.

Dexamethasone-Loaded Chitosan Beads Coated with a pH-Dependent Interpolymer Complex for Colon-Specific Drug Delivery

Chitosan (CS) microparticles loaded with dexamethasone were prepared by spray drying, followed by coating with a pH-dependent interpolymer complex based on poly(acrylic acid)/poly(vinyl pyrrolidone) using an water-in-oil emulsion technique. The aim of this research was to evaluate the influence of PAA/PVP coating on the release of dexamethasone from loaded chitosan microparticles, in simulated gastric fluid (SGF, pH=1.2) and simulated intestinal fluid (SIF, pH=6.8). The release of dexamethasone from uncoated loaded CS microparticles was similar in both fluids, and almost complete release of the drug was achieved in 5 hours. In the coated loaded CS microparticles, the release of dexamethasone in SGF was reduced considerably, very close to zero, due to the interpolymer complex formation at low pH, demonstrating that this system applied as pH-dependent coating has a potential as a site-specific delivery system.

Promising Chitosan-Coated Alginate-Tween 80 Nanoparticles as Rifampicin Coadministered Ascorbic Acid Delivery Carrier Against Mycobacterium tuberculosis

The aim of this study was to design a nanocarrier system for inhalation delivery of rifampicin (RIF) in combination with ascorbic acid (ASC), namely constituted of sodium alginate coated with chitosan and Tween 80 (RIF/ASC NPs) as a platform for the treatment of pulmonary tuberculosis infection. A Box-Behnken experimental design and response surface methodology (RSM) were applied to elucidate and evaluate the effects of several factors on the nanoparticle properties. On the other hand, it was found that RIF/ASC NPs were less cytotoxic than the free RIF, showing a significantly improved activity against nine clinical strains of Mycobacterium tuberculosis (M. tb) in comparison with the free drug. RIF/ASC NPs had an average particle size of 324.0 ± 40.7 nm, a polydispersity index of 0.226 ± 0.030, and a zeta potential of - 28.52 ± 0.47 mV and the surface was hydrophilic. The addition of sucrose (1% w/v) to the nanosuspension resulted in the formation of a solid pellet easily redispersible after lyophilization. RIF/ASC NPs were found to be stable at different physiological pH values. In summary, findings of this work highlight the potential of the RIF/ASC NP-based formulation development herein to deliver RIF in combination with ASC through pulmonary route by exploring a non-invasive route of administration of this antibiotic, increasing the local drug concentrations in lung tissues, the primary infection site, as well as reducing the risk of systemic toxicity and hence improving the patient compliance.

Evaluation of glycerol encapsulated with alginate and alginate-chitosan polymers in gut environment and its resistance to rumen microbial degradation

OBJECTIVE

To determine the effect of gut pH and rumen microbial fermentation on glycerol encapsulated in alginate and alginate-chitosan polymers.

METHODS

Glycerol was encapsulated at 2.5%, 5%, 7.5%, or 10% (w/w) with sodium alginate (A) and alginate-chitosan (AC) polymers. Surface morphology and chemical modifications of the beads were evaluated using scanning electron microscopy and Fourier transform infrared (FTIR) spectra. Encapsulation efficiency was determined at the 5% glycerol inclusion level in two experiments. In experiment 1, 0.5 g of alginate-glycerol (AG) and alginate-chitosan glycerol (ACG) beads were incubated for 2 h at 39°C in pH 2 buffer followed by 24 h in pH 8 buffer to simulate gastric and intestinal conditions, respectively. In experiment 2, 0.5 g of AG and ACG beads were incubated in pH 6 buffer at 39°C for 8 h to simulate rumen conditions. All incubations were replicated four times. Free glycerol content was determined using a spectrophotometer and used to assess loading capacity and encapsulation efficiency. An in vitro experiment with mixed cultures of rumen microbes was conducted to determine effect of encapsulation on microbial fermentation. Data were analyzed according to a complete block design using the MIXED procedure of SAS (SAS Institute, Cary, NC, USA).

RESULTS

For AG and ACG, loading capacity and efficiency were 64.7%, 74.7%, 70.3%, and 78.1%, respectively. Based on the FTIR spectra and scanning electron microscopy, ACG treatment demonstrated more intense and stronger ionic bonds. At pH 6, 36.1% and 29.7% of glycerol was released from AG and ACG, respectively. At pH 2 minimal glycerol was released but pH 8 resulted in 95.7% and 93.9% of glycerol released from AG and ACG, respectively. In vitro microbial data show reduced (p<0.05) fermentation of encapsulated glycerol after 24 h of incubation.

CONCLUSION

The AC polymer provided greater protection in acidic pH with a gradual release of intact glycerol when exposed to an alkaline pH.

Kinetics and Mechanisms of Chemical and Biological Agents Release from Biopolymeric Microcapsules

Kinetics and mechanisms of copper cations and Trichoderma viride spores release from uncoated and chitosan coated alginate microcapsules were investigated. The gelation of a fixed amount of sodium alginate at different concentrations of copper ion solutions resulted in distinct kinetics and release mechanisms. The increase in copper cation concentration promoted, but the presence of the chitosan layer on the microcapsule surface and the increase in microcapsule size reduced the rate of active agent release. Fitting to simple Korsmeyer-Peppas empirical model revealed that the underlying release mechanism (Fickian diffusion or a combination of the diffusion and erosion mechanisms) depends on the copper cation concentration and presence of T. viride spores. The investigation pointed out that the proper selection of formulation variables helps in designing microcapsules with the desirable release of copper ions and T. viride for plant protection and nutrition.

Effects of pH on the Shape of Alginate Particles and Its Release Behavior

A vast majority of alginate particles exist as spheres in most practical uses, and both the particle shape and size are the key factors dominating the applications and performance of alginate gels. Therefore, it becomes an issue of great interest to investigate the aspheric alginate particles. As the first step, various shaped alginate particles were formed due to various pH values in gelation solutions. It was experimentally demonstrated that a low pH brought about an oblate shape, and particularly lower concentrations of both alginate and divalent cations resulted in a flattened oblate shape. Ba2+acting as a cross-linker had a less impact on the particle shape than Ca2+due to a higher affinity in alginate intermolecular cross-linking. With a larger surface area, an oblate particle offered a higher release rate than a spheric one.

Alginate: properties and biomedical applications

Alginate is a biomaterial that has found numerous applications in biomedical science and engineering due to its favorable properties, including biocompatibility and ease of gelation. Alginate hydrogels have been particularly attractive in wound healing, drug delivery, and tissue engineering applications to date, as these gels retain structural similarity to the extracellular matrices in tissues and can be manipulated to play several critical roles. This review will provide a comprehensive overview of general properties of alginate and its hydrogels, their biomedical applications, and suggest new perspectives for future studies with these polymers.

The effect of chitosan as internal or external coating on the 5-ASA release from calcium alginate microparticles

The effect of chitosan as internal or external coating on the mesalamine (5-ASA) release from calcium alginate microparticles (CaAl) was studied, and a delayed release of 5-ASA system intended for colonic drug delivery was developed. The external chitosan coating was developed by immersion of wetted CaAl in chitosan solution and the internal coating by mixing 5-ASA with chitosan solution and drying before the preparation of CaAl. Both systems were coated with Acryl-EZE® using combined fluid bed coating and immersion procedure. The results showed that in phosphate medium (pH 7.5), chitosan as 5-ASA coating promotes a quick erosion process accelerating drug release, but chitosan as external coating (CaAlCS) does not increase the T (50) value compared with the microparticles without chitosan (CaAl). Chitosan as internal or external coating was not effective to avoid the quick 5-ASA release in acidic medium (pH 1.2). The presence of β-glucosidase enzymes increases significantly the 5-ASA release for CaAl, while no effect was observed with chitosan as internal or external coating. Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray data revealed that 5-ASA did not form a solid solution but was dispersed in the microparticles. The Acryl-EZE® coating of microparticles was effective because all the formulations showed a low release, less than 15%, of 5-ASA in acid medium at pH 1.2. Significant differences in the percentage of 5-ASA released between formulations were observed in phosphate buffer at pH 6.0. In phosphate buffer at pH 7.2, all the formulations released 100% of 5-ASA.