Time-Separated Pulse Release-Activation of an Enzyme from Alginate-Polyethylenimine Hydrogels Using Electrochemically Generated Local pH Changes.

ß-Glucosidase (EC 3.2.1.21) from sweet almond was encapsulated into pH-responsive alginate-polyethylenimine (alginate-PEI) hydrogel. Then, electrochemically controlled cyclic local pH changes resulting from ascorbate oxidation (acidification) and oxygen reduction (basification) were used for the pulsatile release of the enzyme from the composite hydrogel. Activation of the enzyme was controlled by the very same pH changes used for ß-glucosidase release, separating these two processes in time. Importantly, the activity of the enzyme, which had not been released yet, was inhibited due to the buffering effect of PEI present in the gel. Thus, only a portion of the released enzyme was activated. Both enzymatic activity and release were monitored by confocal fluorescence microscopy and regular fluorescent spectroscopy. Namely, commercially available very little or nonfluorescent substrate 4-methylumbelliferyl-ß-d-glucopyranoside was hydrolyzed by ß-glucosidase to produce a highly fluorescent product 4-methylumbelliferone during the activation phase. At the same time, labeling of the enzyme with rhodamine B isothiocyanate was used for release observation. The proposed work represents an interesting smart release-activation system with potential applications in biomedical field.

Electrospray Nano-Micro Composite Sodium Alginate Microspheres with Shape-Adaptive, Antibacterial, and Angiogenic Abilities for Infected Wound Healing.

Nonhealing infectious wounds, characterized by bacterial colonization, wound microenvironment destruction, and shape complexity, present an intractable problem in clinical practice. Inspired by LEGOs, building-block toys that can be assembled into desired shapes, we proposed the use of electrospray nano-micro composite sodium alginate (SA) microspheres with antibacterial and angiogenic properties to fill irregularly shaped wounds instantly. Specifically, porous poly(lactic-co-glycolic acid) (PLGA) microspheres (MSs) encapsulating basic fibroblast growth factor (bFGF) were produced by a water-in-oil-in-water double-emulsion method. Then, bFGF@MSs were blended with the SA solution containing ZIF-8 nanoparticles. The resultant solution was electrosprayed to obtain nano-micro composite microspheres (bFGF@MS/ZIF-8@SAMSs). The composite MSs' size could be regulated by PLGA MS mass proportion and electrospray voltage. Moreover, bFGF, a potent angiogenic agent, and ZIF-8, bactericidal nanoparticles, were found to release from bFGF@MS/ZIF-8@SAMSs in a controlled and sustainable manner, which promoted cell proliferation, migration, and tube formation and killed bacteria. Through experimentation on rat models, bFGF@MS/ZIF-8@SAMSs were revealed to adapt to wound shapes and accelerate infected wound healing because of the synergistic effects of antibacterial and angiogenic abilities. In summation, this study developed a feasible approach to prepare bioactive nano-micro MSs as building blocks that can fill irregularly shaped infected wounds and improve healing.

Evaluation of alginate-coated ß-tricalcium phosphate fiber scaffold for cell culture.

Ex vivo tissue engineering is an effective therapeutic approach for the treatment of severe cartilage diseases that require tissue replenishment or replacement. This strategy demands scaffolds that are durable enough for long-term cell culture to form artificial tissue. Additionally, such scaffolds must be biocompatible to prevent the transplanted matrix from taking a toll on the patient's body. From the viewpoint of structure and bio-absorbability, a ß-tricalcium phosphate (ß-TCP) fiber scaffold (ßTFS) is expected to serve as a good scaffold for tissue engineering. However, the fragility and high solubility of ß-TCP fibers make this matrix unsuitable for long-term cell culture. To solve this problem, we developed an alginate-coated ß-TCP fiber scaffold (ßTFS-Alg). To assess cell proliferation and differentiation in the presence of ßTFS-Alg, we characterized ATDC5 cells, a chondrocyte-like cell line, when grown in this matrix. We found that alginate coated the surface of ßTFS fiber and suppressed the elution of Ca2+ from ß-TCP fibers. Due to the decreased solubility of ßTFS-Alg compared with ß-TCP, the former provided an improved scaffold for long-term cell culture. Additionally, we observed superior cell proliferation and upregulation of chondrogenesis marker genes in ATDC5 cells cultured in ßTFS-Alg. These results suggest that ßTFS-Alg is suitable for application in tissue culture.

The use of fluid-phase 3D printing to pattern alginate-gelatin hydrogel properties to guide cell growth and behaviourin vitro.

Three-dimensional (3D) (bio)printing technology has boosted the advancement of the biomedical field. However, tissue engineering is an evolving field and (bio)printing biomimetic constructions for tissue formation is still a challenge. As a new methodology to facilitate the construction of more complex structures, we suggest the use of the fluid-phase 3D printing to pattern the scaffold's properties. The methodology consists of an exchangeable fluid-phase printing medium in which the constructions are fabricated and patterned during the printing process. Using the fluid-phase methodology, the biological and mechanical properties can be tailored promoting cell behaviour guidance and compartmentalization. In this study, we first assessed different formulations of alginate/gelatin to create a stable substrate capable to promote massive cell colonizationin vitroover time. Overall, formulations with lower gelatin content and 2-(N-morpholino)ethanesulfonic acid (MES) buffer as a solvent showed better stability under cell culture conditions and enhanced U2OS cell growth. Next, the fluid-phase showed better printing fidelity and resolution in comparison to air printing as it diminished the collapsing and the spread of the hydrogel strand. In sequence, the fluid-phase methodology was used to create functionalized alginate-gelatin-arginylglycylaspartic acid peptide (RGD) hydrogels via carbodiimides chemistry. The alginate-gelatin-RGD hydrogels showed an increase of 2.97-fold in cell growth and more spread substrate colonization in comparison to alginate-gelatin hydrogel. Moreover, the fluid-phase methodology was used to add RGD molecules to pre-determined parts of the alginate-gelatin substrate during the printing process promoting U2OS cell compartmentalization. In addition, different substrate stiffnesses were also created via fluid-phase by crosslinking the hydrogel with different concentrations of CaCl2during the printing process. As a result, the U2OS cells were also compartmentalized on the stiffer parts of the printings. Finally, our results showed that by combining stiffer hydrogel with RGD increasing concentrations we can create a synergetic effect and boost cell metabolism by up to 3.17-fold. This work presents an idea of a new printing process for tailoring multiple parameters in hydrogel substrates by using fluid-phase to generate more faithful replication of thein vivoenvironment.

Physicochemical properties and fractal characterizations of the functionalized porous clinoptilolites for controlling alginate delivery in growing cauliflower and leaf mustard.

Using natural clinoptilolite (NCP) as a carrier and alginate (Alg)-calcium as an active species, the porous silicon calcium alginate nanocomposite (Alg-Ca-NCP) was successfully fabricated via adsorption-covalence-hydrogen bond. Its structural features and physicochemical properties were detailed investigated by various characterizations. The results indicated that Alg-Ca-NCP presented the disordered lamellar structures with approximately uniform particles in size of 300-500 nm. Specially, their surface fractal evolutions between the irregular roughness and dense structures were demonstrated via the SAXS patterns. The results elucidated that the abundant micropores of NCP were beneficial for unrestricted diffusing of Alg-Ca, which was conducive to facilitate a higher loading and sustainable releasing. The Ca content of leaf mustard treated with Alg-Ca-NCP-0.5 was 484.5 mg/100g on the 21st day, higher than that by water (CK) and CaCl2 solution treatments, respectively. Meanwhile, the prepared Alg-Ca-NCPs presented the obvious anti-aging effects on peroxidase drought stress of mustard leaves. These demonstrations provided a simple and effective method to synthesize Alg-Ca-NCPs as delivery nanocomposites, which is useful to improve the weak absorption and low utilization of calcium alginate by plants.

Transforming the Stability, Encapsulation, and Sustained Release Properties of Calcium Alginate Beads through Gel-Confined Coacervation.

Calcium alginate (Ca2+/alginate) gel beads find use in diverse applications, ranging from drug delivery and tissue engineering to bioprocessing, food formulation, and agriculture. Unless modified, however, these gels have limited stability in alkaline media (including phosphate buffers), and their high solute permeability limits their ability to efficiently encapsulate and slowly release water-soluble small molecules. Here, we show how these limitations can be addressed by mixing the alginate solutions used in the bead preparation with the nontoxic anionic polymer polyphosphate (PP). Upon complexing Ca2+ ions, PP undergoes complex coacervation (i.e., liquid/liquid phase separation into a Ca2+/PP-rich coacervate phase and a dilute supernatant phase). At lower PP concentrations, the Ca2+/PP coacervate appears to simply remain dispersed within the beads. Though its presence makes the beads more stable in alkaline media (phosphate-buffered saline and seawater), it has little impact on the bead stiffness, morphology, and (at least in the absence of substantial payload/coacervate association) encapsulation and release properties. When the PP concentrations exceed a critical value, however, Ca2+/PP coacervation within the gelling Ca2+/alginate beads collapses the resulting beads into more compact, interpenetrating polymer networks. Besides their enhanced stability to alkaline environments, these hybrid beads exhibit irregular morphologies with wrinkled and dimpled surface structures and macroscopic (closed) internal pores, and their collapse into these polymer-rich networks also makes them significantly stiffer than their PP-free counterparts. Crucially, these beads also exhibit a much lower solute permeability, which enables highly efficient encapsulation and multiday release of water-soluble small molecules (with the beads encapsulating >90% of the added model payload and sustaining its release over 3-5 d). Collectively, these findings provide a mild and simple (single-step) pathway to generating ionically cross-linked alginate beads with significantly enhanced stability, encapsulation efficiency, and sustained release.

Self-Assembly Reinforced Alginate Fibers for Enhanced Strength, Toughness, and Bone Regeneration.

Material reinforcement commonly exists in a contradiction between strength and toughness enhancement. Herein, a reinforced strategy through self-assembly is proposed for alginate fibers. Sodium alginate (SA) microstructures with regulated secondary structures are assembled in acidic and ethanol as reinforcing units for alginate fibers. Acidity increases the flexibility of the helix and contributes to enhanced extendibility. Ethanol is responsible for formation of a stiff ß-sheet, which enhances the modulus and strength. The structurally engineered SA assembly exhibits robust mechanical compatibility, and thus reinforced alginate fibers possess an improved tensile strength of 2.1 times, a prolonged elongation of 1.5 times, and an enhanced toughness of 3.0 times compared with SA fibers without reinforcement. The reinforcement through self-assembly provides an understanding of strengthening and toughening mechanism based on secondary structures. Due to a similar modulus with bones, reinforced alginate fibers exhibit good efficacy in accelerating bone regeneration in vivo.

Rational design of PspAlgL to improve its thermostability and anti-biofilm activity against Pseudomonas aeruginosa.

Pseudomonas aeruginosa biofilm enhances tolerance to antimicrobials and immune system defenses. Alginate is an important component of biofilm and a virulence factor of P. aeruginosa. The degradation of alginate by alginate lyases has come to serve as an adjunctive therapeutic strategy against P. aeruginosa biofilm, but poor stability of the enzyme limited this application. Thus, PspAlgL, an alginate lyase, can degrade acetylated alginate but has poor thermostability. The 3D structure of PspAlgL was predicted, and the thermostability of PspAlgL was rationally designed by GRAPE strategy, resulting in two variants with better stability. These variants, PspAlgLS270F/E311P and PspAlgLG291S/E311P, effectively degraded the alginate in biofilm. In addition, compared with PspAlgL, these variants were more efficient in inhibiting biofilm formation and degrading the established biofilm of P. aeruginosa PAO1, and they were also able to destroy the biofilm attached to catheters and to increase the sensitivity of P. aeruginosa to the antibiotic amikacin. This study provides one potential anti-biofilm agent for P. aeruginosa infection.

Bioremediation of 2,4,6-trichlorophenol by extracellular enzymes of white rot fungi immobilized with sodium alginate/hydroxyapatite/chitosan microspheres.

Hydroxyapatite, a calcium phosphate biomass material known for its excellent biocompatibility, holds promising applications in water, soil, and air treatment. Sodium alginate/hydroxyapatite/chitosan (SA-HA-CS) microspheres were synthesized by cross-linking sodium alginate with calcium chloride. These microspheres were carriers for immobilizing extracellular crude enzymes from white rot fungi through adsorption, facilitating the degradation of 2,4,6-trichlorophenol (2,4,6-TCP) in water and soil. At 50 °C, the immobilized enzyme retained 87.2% of its maximum activity, while the free enzyme activity dropped to 68.86%. Furthermore, the immobilized enzyme maintained 68.09% of its maximum activity at pH 7, surpassing the 51.16% observed for the free enzyme. Under optimal conditions (pH 5, 24 h), the immobilized enzymes demonstrated a remarkable 94.7% removal rate for 160 mg/L 2,4,6-TCP, outperforming the 62.1% achieved by free crude enzymes. The degradation of 2,4,6-TCP by immobilized and free enzymes adhered to quasi-first-order degradation kinetics. Based on LC-MS, the plausible biodegradation mechanism and reaction pathway of 2,4,6-TCP were proposed, with the primary degradation product identified as 1,2,4-trihydroxybenzene. The immobilized enzyme effectively removed 72.9% of 2,4,6-TCP from the soil within 24 h. The degradation efficiency of the immobilized enzyme varied among different soil types, exhibiting a negative correlation with soil organic matter content. These findings offer valuable insights for advancing the application of immobilized extracellular crude enzymes in 2,4,6-TCP remediation.

Technique for Rapidly Forming Networks of Microvessel-Like Structures.

Modeling organ-blood barriers through the inclusion of microvessel networks within in vitro tissue models could lead to more physiologically accurate results, especially since organ-blood barriers are crucial to the normal function, drug transport, and disease states of vascularized organs. Microvessel networks are difficult to form, since they push the practical limits of most fabrication methods, and it is difficult to coax vascular cells to self-assemble into structures larger than capillaries. Here, we present a method for rapidly forming networks of microvessel-like structures using sacrificial alginate structures. Specifically, we encapsulated endothelial cells within short alginate threads, and then embedded them in collagen gel. Following enzymatic degradation of the alginate, the collagen gel contained a network of hollow channels seeded with cells, all surrounding a perfusable central channel. This method uses a 3D-printed coaxial extruder and syringe pumps to generate short threads in a way that is repeatable and easily transferrable to other labs. The cell-laden, sacrificial alginate threads can be frozen after fabrication and thawed before embedding without significant loss of cell viability. The ability to freeze the threads enables future scale-up and ease of use. Within millifluidic devices that restrict access to media, the threads enhance cell survival under static conditions. These results indicate the potential for use of this method in a range of tissue engineering applications.

Interpenetrating gelatin/alginate mixed hydrogel: The simplest method to prepare an autoclavable scaffold.

The choice of sterilization method for hydrogels used for cell culture influences the ease of preparing the gel. We prepared interpenetrating gelatin/calcium alginate hydrogels containing 1% (w/v) alginate and 1-16% (w/v) gelatin by molding with the mixture of gelatin/sodium alginate solution, followed by the addition of calcium ions by incubation in calcium chloride solution. It is the simplest method to prepare autoclavable gelatin/sodium hydrogel. We measured various properties of the hydrogels including volume, Young's modulus in the compression test, storage modulus, and loss modulus in the dynamic viscoelasticity measurement. The gelatin/alginate hydrogel can be easily fabricated into any shape by this method. After autoclave treatment, the hydrogel was shrunk to smaller than the original shape in similar figures. The shape of the gelatin/alginate hydrogel can be designed into any shape with the reduction ratio of the volume. Human osteosarcoma (HOS) cells adhered to the gelatin/alginate hydrogel and then proliferated. Gelatin/calcium alginate hydrogels with a high concentration are considered to be autoclavable culture substrates because of their low deformation and gelatin elution rate after autoclaving and the high amount of cells attached to the hydrogels.

A novel, microfluidic high-throughput single-cell encapsulation of human bone marrow mesenchymal stromal cells.

The efficacy of stem-cell therapy depends on the ability of the transplanted cells to escape early immunological reactions and to be retained at the site of transplantation. The use of tissue engineering scaffolds or injectable biomaterials as carriers has been proposed, but they still present limitations linked to a reliable manufacturing process, surgical practice and clinical outcomes. Alginate microbeads are potential candidates for the encapsulation of mesenchymal stromal cells with the aim of providing a delivery carrier suitable for minimally-invasive and scaffold-free transplantation, tissue-adhesive properties and protection from the immune response. However, the formation of stable microbeads relies on the cross-linking of alginate with divalent calcium ions at concentrations that are toxic for the cells, making control over the beads' size and a single-cell encapsulation unreliable. The present work demonstrates the efficiency of an innovative, high throughput, and reproducible microfluidic system to produce single-cell, calcium-free alginate coatings of human mesenchymal stromal cells. Among the various conditions tested, visible light and confocal microscopy following staining of the cell nuclei by DAPI showed that the microfluidic system yielded an optimal single-cell encapsulation of 2000 cells/min in 2% w/v alginate microcapsules of reproducible morphology and an average size of 28.2 ± 3.7 µm. The adhesive properties of the alginate microcapsules, the viability of the encapsulated cells and their ability to escape the alginate microcapsule were demonstrated by the relatively rapid adherence of the beads onto tissue culture plastic and the cells' ability to gradually disrupt the microcapsule shell after 24 h and proliferate. To mimic the early inflammatory response upon transplantation, the encapsulated cells were exposed to proliferating macrophages at different cell seeding densities for up to 2 days and the protection effect of the microcapsule on the cells assessed by time-lapse microscopy showing a shielding effect for up to 48 h. This work underscores the potential of microfluidic systems to precisely encapsulate cells by good manufacturing practice standards while favouring cell retention on substrates, viability and proliferation upon transplantation.

Charge neutralization and ß-elimination cleavage mechanism of family 42 L-rhamnose-α-1,4-D-glucuronate lyase revealed using neutron crystallography.

Gum arabic (GA) is widely used as an emulsion stabilizer and edible coating and consists of a complex carbohydrate moiety with a rhamnosyl-glucuronate group capping the non-reducing ends. Enzymes that can specifically cleave the glycosidic chains of GA and modify their properties are valuable for structural analysis and industrial application. Cryogenic X-ray crystal structure of GA-specific L-rhamnose-α-1,4-D-glucuronate lyase from Fusarium oxysporum (FoRham1), belonging to the polysaccharide lyase (PL) family 42, has been previously reported. To determine the specific reaction mechanism based on its hydrogen-containing enzyme structure, we performed joint X-ray/neutron crystallography of FoRham1. Large crystals were grown in the presence of L-rhamnose (a reaction product), and neutron and X-ray diffraction datasets were collected at room temperature at 1.80 and 1.25 Å resolutions, respectively. The active site contained L-rhamnose and acetate, the latter being a partial analog of glucuronate. Incomplete H/D exchange between Arg166 and acetate suggested that a strong salt-bridge interaction was maintained. Doubly deuterated His105 and deuterated Tyr150 supported the interaction between Arg166 and the acetate. The unique hydrogen-rich environment functions as a charge neutralizer for glucuronate and stabilizes the oxyanion intermediate. The NE2 atom of His85 was deprotonated and formed a hydrogen bond with the deuterated O1 hydroxy of L-rhamnose, indicating the function of His85 as the base/acid catalyst for bond cleavage via ß-elimination. Asp83 functions as a pivot between the two catalytic histidine residues by bridging them. This His-His-Asp structural motif is conserved in the PL 24, 25, and 42 families.

Simultaneous adsorption of chromate and arsenate onto ferrihydrite/alginate composite beads: Competition and mechanism.

Ferrihydrite is an effective adsorbent of chromate and arsenate. In order to gain insight into the application of ferrihydrite in water treatment, macroporous alginate/ferrihydrite beads, synthesized using two different methods (internal and encapsulation processes), were used in this work. The properties of the ferrihydrite were assessed using various techniques, including X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) theory, and zetametry. The results showed that the specific surface area of the ferrihydrite was 242 m2/g, and the PZC was pH8. The kinetic and isotherm adsorption properties of the ferrihydrite were evaluated in this study. The results indicate that the pseudo second-order and Freundlich models accurately describe the kinetic and isotherm adsorption properties of chromates and arsenates. For chromate removal, ferrihydrite exhibited a relatively high adsorption capacity (40.7 mgCr/g) compared to other adsorbents. However, the arsenate adsorption capacity of MFHB-SI (140.8 mgAs/g) was shown to be the most optimal. The internal synthesis process was suitable for arsenate retention due to the resulting arsenate precipitation. The competitive adsorption analyses indicated that the presence of chromate does not limit the adsorption of arsenate. However, the presence of arsenate almost completely inhibits the adsorption of chromate when the arsenate concentration is above 50 mg/L, due to the precipitation reaction of arsenate.

Adeno-Associated Virus-Encapsulated Alginate Microspheres Loaded in Collagen Gel Carriers for Localized Gene Transfer.

This work reports localized in vivo gene transfer by biodegradation of the adeno-associated virus-encapsulating alginate microspheres (AAV-AMs) loaded in collagen gel carriers. AAV-AMs are centrifugally synthesized by ejecting a mixed pre-gel solution of alginate and AAV to CaCl2 solution to form an ionically cross-linked hydrogel microsphere immediately. The AAV-AMs are able to preserve the AAV without diffusing out even after spreading them on the cells, and the AAV is released and transfected by the degradation of the alginate microsphere. In addition, AAV-AMs can be stored by cryopreservation until use. By implanting this highly convenient AAV-encapsulated hydrogel, AAV-AMs can be loaded into collagen gel carriers to fix the position of the implanted AAV-AMs and achieve localized gene transfer in vivo. In vivo experiments show that the AAV-AMs loaded in collagen gel carriers are demonstrated to release the encapsulated AAV for gene transfer in the buttocks muscles of mice. While conventional injections caused gene transfer to the entire surrounding tissue, the biodegradation of AAV-AMs shows that gene transfer is achieved locally to the muscles. This means that the proposed AAV-loaded system is shown to be a superior method for selective gene transfer.

Multichannel Multijunction Droplet Microfluidic Device to Synthesize Hydrogel Microcapsules with Different Core-Shell Structures and Adjustable Core Positions.

Core-shell hydrogel microcapsules have sparked great interest due to their unique characteristics and prospective applications in the medical, pharmaceutical, and cosmetic fields. However, complex synthetic procedures and expensive costs have limited their practical application. Herein, we designed and prepared several multichannel and multijunctional droplet microfluidic devices based on soft lithography for the effective synthesis of core-shell hydrogel microcapsules for different purposes. Additionally, two different cross-linking processes (ultraviolet (UV) exposure and interfacial polymerization) were used to synthesize different types of core-shell structured hydrogel microcapsules. Hydrogel microcapsules with gelatin methacryloyl (GelMA) as the core and polyacrylamide (PAM) as the thin shell were synthesized using UV cross-linking. Using an interfacial polymerization process, another core-shell structured microcapsule with GelMA as the core and Ca2+ cross-linked alginate with polyethylenimine (PEI) as the shell was constructed, and the core diameter and total droplet diameter were flexibly controlled by carving. Noteworthy, these hydrogel microcapsules exhibit stimuli-responsiveness and controlled release ability. Overall, a novel technique was developed to successfully synthesize various hydrogel microcapsules with core-shell microstructures. The hydrogel microcapsules possess a multilayered structure that facilitates the coassembly of cells and drugs, as well as the layered assembly of multiple drugs, to develop synergistic therapeutic regimens. These adaptable and controllable hydrogel microdroplets shall held great promise for multicell or multidrug administration as well as for high-throughput drug screening.

Assessment of calcium alginate gels as wall materials for encapsulation systems.

BACKGROUND: Calcium alginate gels are widely used to encapsulate active compounds. Some characteristic parameters of these gels are necessary to describe the release of active compounds through mechanistic mathematical models. In this work, transport and kinetics properties of calcium alginate gels were determined through simple experimental techniques. RESULTS: The weight-average molecular weight ( M ¯ w = 192 × 103 Da) and the fraction of residues of α-l-guluronic acid ( F G = 0.356) of sodium alginate were determined by capillary viscometry and 1 H-nuclear magnetic resonance at 25 °C, respectively. Considering the half egg-box model, both values were used to estimate the molecular weight of calcium alginate as M g = 2.02 × 105 Da. An effective diffusion coefficient of water ( D eff , w = 2.256 × 10-9 m2 s-1 ) in calcium alginate was determined using a diffusion cell at 37 °C. Finally, a kinetics constant of depolymerization ( k m = 9.72 × 10-9 m3 mol-1 s-1 ) of calcium alginate was obtained considering dissolution of calcium to a medium under intestinal conditions. CONCLUSION: The experimental techniques used are simple and easily reproducible. The obtained values may be useful in the design, production, and optimization of the alginate-based delivery systems that require specific release kinetics of the encapsulated active compounds. © 2023 Society of Chemical Industry.

Development of alginate beads for precise environmental release applications: A design of experiment based approach and analysis.

Controlled release of active ingredients are important for drug delivery and more recently environmental applications including modulated dosing of chemical and biological controls. This study demonstrates the importance of investigating various material science factors that can influence the diffusion rates of alginate beads to improve and tune their performance for marine environmental applications. This investigation aimed to design a rational workflow to aid in leveraging alginate bead use as a carrier matrix for releasing a specific active agent into water. Experiments were conducted to focus on the narrow a large list of relevant material formulation parameters, which included chitosan molecular weight, chitosan concentration, calcium concentration, drop height, and bead size. Once the most relevant material preparation methods were screened, a more robust statistic Design of Experiments approach was performed and results determined the important (and unimportant) factors for increasing dye release kinetics in marine water. The process was further streamlined by narrowing the critical experimental factors to a three-level based on the prior analysis: chitosan MW, chitosan concentration, and bead size. Analysis of the collected data indicated that while chitosan MW had a negligible impact (Fstatistic = 0.22), bead size (Fstatistic = 60.33) significantly influenced the diffusion rates based on surface area. However, chitosan MW had minor effects where lower chitosan MW enabled higher product release rates. This case investigation was a novel application of the design of experiment approach towards environmental applications to understand differences in release rates to marine waters for the first time and the workflow provided also serve as the basis for researchers to optimize other environmental applications requiring optimization when it is unknown how a large number of formulation variables will impact performance in different environmental scenarios.

Ions-Induced Alginate Gelation According to Elemental Analysis and a Combinatorial Approach.

This study considers the potential of elemental analysis of polysaccharide ionotropic gels in elucidating the junction zones for different divalent cations. The developed algorithm ensures the correct separation of contributions from physically adsorbed and structure-forming ionic compounds, with the obtained results scaled to alginate C12 block. Possible versions of chain association into dimers and their subsequent integration into flat junction zones were analyzed within the framework of the "egg-box" model. The application of combinatorial analysis made it possible to derive theoretical relations to find the probability of various types of egg-box cell occurrences for alginate chains with arbitrary monomeric units ratio µ = M/G, which makes it possible to compare experimental data for alginates of different origins. Based on literature data and obtained chemical formulas, the possible correspondence of concrete biopolymer cells to those most preferable for filling by alkaline earth cations was established. The identified features of elemental composition suggest the formation of composite hydrated complexes with the participation of transition metal cations. The possibility of quantitatively assessing ordered secondary structures formed due to the physical sorption of ions and molecules from environment, correlating with the sorption capabilities of Me2+ alginate, was established.

Development and characterization of letrozole-encapsulated polymeric beads for sustained release.

The study aimed to prepare and characterize biodegradable sustained-release beads of letrozole (LTZ) for treating cancerous disease. The ionotropic gelation method was used for the preparation and calcium chloride (CaCl2) was used as a gelating agent, while chitosan (CTS) and sodium alginate (NaAlg) as biodegradable polymeric matrices in the blend hydrogel beads. The beads were characterized for their size, surface morphology, drug entrapment efficiency, drug-polymer interaction and crystallinity using different analytic techniques, including optical microscopy, Scanning Electron Microscopy (SEM), UV-spectroscopy, Fourier-transform Infrared Spectroscopy (FTIR), Thermo gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and X-ray Diffraction Analysis (XRD) respectively. In vitro swelling studies were also applied to observe the response of these polymeric networks against different pH (at 1.2, 6.8 and 7.4 pH). The results from TGA and DSC exhibited that the components in the formulation possess better thermal stability. The XRD of polymeric networks displays a minor crystalline and significant amorphous nature. The SEM micrographs revealed that polymeric networks have uneven surfaces and grooves. Better swelling and in vitro outcomes were achieved at a high pH (6.8,7.4), which endorsed the pH-responsive characteristics of the prepared beads. Hence, beads based on chitosan and sodium alginate were successfully synthesized and can be used for the controlled release of letrozole.