Sustained delivery of vascular endothelial growth factor with alginate beads

A Green, Solvent- and Cation-Free Approach for Preparing 5-Fluorouracil-Loaded Alginate Nanoparticles Using Microfluidic Technology

Background/Objectives: Alginate nanoparticles (NPs) are commonly synthesised using either an emulsion technique that involves organic solvent use or ionotropic gelation utilising multivalent cations, e.g., Ca+2. However, the extensive use of organic solvents imposes detrimental effects on the ecosystem, and using multivalent cations as crosslinkers could eventually lead to the leakage of these cations, thus disrupting nanoparticle matrices. Therefore, this study aimed to overcome the limitations of these techniques by eliminating the usage of organic solvents and multivalent cations. Methods: In this research, alginate nanoparticles were synthesised using proton gelation by microfluidic technology through protonating alginate carboxylate groups to crosslink alginate chains through H-bond formation. Results: The prepared acid-gelled alginate nanoparticles demonstrated an MHD circa 200 nm and a PDI of less than 0.4 at pH 0.75. Moreover, 5-FU was successfully encapsulated into acid-gelled alginate nanoparticles and displayed a high EE% of around 30%, comparable to the EE% at high alginate concentration and molecular weight (0.4 H-ALG) achieved by Ca+2-crosslinked alginate nanoparticles; however, 5-FU NPs had superior characteristics, i.e., a lower MHD (around 500 nm) and PDI (<0.5). The optimum formula (0.4 H-ALG) was explored at various pH values, i.e., low pH of 4.5 and high pH of 10, and alginate NPs produced by acid gelation demonstrated high stability in terms of MHD and PDI, with slight changes at different pH values, indicating stable crosslinking of alginate matrices prepared by technology compared with Ca+2-crosslinked alginate NPs. Conclusions: In conclusion, this research has invented an ecologically friendly approach to producing acid-gelled alginate nanoparticles with superior characteristics compared with the conventional methods, and they could be harnessed as nanocarriers for therapeutics delivery (5-FU). Also, this research offers a promising approach for developing eco-friendly and biocompatible drug carriers. The produced nanoparticles have the potential to enhance drug stability, improve controlled release, and minimise toxic effects, making them suitable for pharmaceutical applications.

Actuation-Mediated Compression of a Mechanoresponsive Hydrogel by Soft Robotics to Control Release of Therapeutic Proteins

Therapeutic proteins, the fastest growing class of pharmaceuticals, are subject to rapid proteolytic degradation in vivo, rendering them inactive. Sophisticated drug delivery systems that maintain protein stability, prolong therapeutic effects, and reduce administration frequency are urgently required. Herein, a mechanoresponsive hydrogel is developed contained within a soft robotic drug delivery (SRDD) device. In a step-change from previously reported systems, pneumatic actuation of this system releases the cationic therapeutic protein Vascular Endothelial Growth Factor (VEGF) in a bioactive form which is required for therapeutic angiogenesis, the growth of new blood vessels, in numerous clinical conditions. The ability of the SRDD device to release bioactive VEGF in a spatiotemporal manner from the hydrogel is tested in diabetic rats - a model in which angiogenesis is difficult to stimulate. Daily actuation of the SRDD device in the diabetic rat model significantly increased cluster of differentiation 31+ (CD31+) blood vessel number (p = 0.0335) and the diameter of alpha-smooth muscle actin+ (α-SMA+) blood vessels (p = 0.0025) compared to passive release of VEGF from non-actuated devices. The SRDD device combined with the mechanoresponsive hydrogel offers the potential to deliver an array of bioactive therapeutics in a spatiotemporal manner to mimic their natural release in vivo.

Postmodification with Polycations Enhances Key Properties of Alginate-Based Multicomponent Microcapsules

Postmodification of alginate-based microspheres with polyelectrolytes (PEs) is commonly used in the cell encapsulation field to control microsphere stability and permeability. However, little is known about how different applied PEs shape the microsphere morphology and properties, particularly in vivo. Here, we addressed this question using model multicomponent alginate-based microcapsules postmodified with PEs of different charge and structure. We found that the postmodification can enhance or impair the mechanical resistance and biocompatibility of microcapsules implanted into a mouse model, with polycations surprisingly providing the best results. Confocal Raman microscopy and confocal laser scanning microscopy (CLSM) analyses revealed stable interpolyelectrolyte complex layers within the parent microcapsule, hindering the access of higher molar weight PEs into the microcapsule core. All microcapsules showed negative surface zeta potential, indicating that the postmodification PEs get hidden within the microcapsule membrane, which agrees with CLSM data. Human whole blood assay revealed complex behavior of microcapsules regarding their inflammatory and coagulation potential. Importantly, most of the postmodification PEs, including polycations, were found to be benign toward the encapsulated model cells.

Hydroxyapatite-loaded macroporous calcium alginate hydrogels: Preparation, characterization, and in vitro evaluation

Hydrogels from natural polysaccharides are of great interest for tissue engineering. This study aims (1) to prepare hydroxyapatite-loaded macroporous calcium alginate hydrogels by novel one-step technique using internal gelation in water-frozen solutions; (2) to evaluate their physicochemical properties; (3) to estimate their ability to support cell growth and proliferation in vitro. The structure of the hydrogel samples in a swollen state was studied by confocal laser scanning microscopy and was shown to represent a system of interconnected macropores with sizes of tens micron. The swelling behavior of the hydrogels, their mechanical properties (Young's moduli) in function of a hydroxyapatite content (5-30 mass%) were studied. All hydrogel samples loaded with hydroxyapatite were found to support growth and proliferation of mouse fibroblasts (L929) at long-term cultivation for 7 days. The obtained macroporous composite Ca-Alg-HA hydrogels could be promising for tissue engineering.

Vascular endothelial growth factor (VEGF) delivery approaches in regenerative medicine

The utilization of growth factors in the process of tissue regeneration has garnered significant interest and has been the subject of extensive research. However, despite the fervent efforts invested in recent clinical trials, a considerable number of these studies have produced outcomes that are deemed unsatisfactory. It is noteworthy that the trials that have yielded the most satisfactory outcomes have exhibited a shared characteristic, namely, the existence of a mechanism for the regulated administration of growth factors. Despite the extensive exploration of drug delivery vehicles and their efficacy in delivering certain growth factors, the development of a reliable predictive approach for the delivery of delicate growth factors like Vascular Endothelial Growth Factor (VEGF) remains elusive. VEGF plays a crucial role in promoting angiogenesis; however, the administration of VEGF demands a meticulous approach as it necessitates precise localization and transportation to a specific target tissue. This process requires prolonged and sustained exposure to a low concentration of VEGF. Inaccurate administration of drugs, either through off-target effects or inadequate delivery, may heighten the risk of adverse reactions and potentially result in tumorigenesis. At present, there is a scarcity of technologies available for the accurate encapsulation of VEGF and its subsequent sustained and controlled release. The objective of this review is to present and assess diverse categories of VEGF administration mechanisms. This paper examines various systems, including polymeric, liposomal, hydrogel, inorganic, polyplexes, and microfluidic, and evaluates the appropriate dosage of VEGF for multiple applications.

Bacterial Viability in Self-Healing Concrete: A Case Study of Non-Ureolytic Bacillus Species

Cracking is an inevitable feature of concrete, typically leading to corrosion of the embedded steel reinforcement and massive deterioration because of the freezing-thawing cycles. Different means have been proposed to increase the serviceability performance of cracked concrete structures. This case study deals with bacteria encapsulated in cementitious materials to "heal" cracks. Such a biological self-healing system requires preserving the bacteria's viability in the cement matrix. Many embedded bacterial spores are damaged during concrete curing, drastically reducing efficiency. This study investigates the viability of commonly used non-ureolytic bacterial spores when immobilized in calcium alginate microcapsules within self-healing cementitious composites. Three Bacillus species were used in this study, i.e., B. pseudofirmus, B. cohnii, and B. halodurans. B. pseudofirmus demonstrated the best mineralization activity; a sufficient number of bacterial spores remained viable after the encapsulation. B. pseudofirmus and B. halodurans spores retained the highest viability after incorporating the microcapsules into the cement paste, while B. halodurans spores retained the highest viability in the mortar. Cracks with a width of about 0.13 mm were filled with bacterial calcium carbonate within 14 to 28 days, depending on the type of bacteria. Larger cracks were not healed entirely. B. pseudofirmus had the highest efficiency, with a healing coefficient of 0.497 after 56 days. This study also revealed the essential role of the cement hydration temperature on bacterial viability. Thus, further studies should optimize the content of bacteria and nutrients in the microcapsule structure.

Advances in Skin Tissue Engineering and Regenerative Medicine

There are an estimated 500,000 patients treated with full-thickness wounds in the United States every year. Fire-related burn injuries are among the most common and devastating types of wounds that require advanced clinical treatment. Autologous split-thickness skin grafting is the clinical gold standard for the treatment of large burn wounds. However, skin grafting has several limitations, particularly in large burn wounds, where there may be a limited area of non-wounded skin to use for grafting. Non-cellular dermal substitutes have been developed but have their own challenges; they are expensive to produce, may require immunosuppression depending on design and allogenic cell inclusion. There is a need for more advanced treatments for devastating burns and wounds. This manuscript provides a brief overview of some recent advances in wound care, including the use of advanced biomaterials, cell-based therapies for wound healing, biological skin substitutes, biological scaffolds, spray on skin and skin bioprinting. Finally, we provide insight into the future of wound care and technological areas that need to be addressed to support the development and incorporation of these technologies.

Development of chondrocyte-laden alginate hydrogels with modulated microstructure and properties for cartilage regeneration

Alginate hydrogel is an attractive biomaterial for cell microencapsulation. The microarchitecture of hydrogels can regulate cellular functions. This study aims to investigate the applicability of sodium citrate buffer (SCB) as a culture medium supplement for modulating the microstructure of alginate microbeads to provide a favorable microenvironment for chondrogenic induction. The chondrocyte-laden microbeads, with and without TGF-β3 incorporation, were produced through an encapsulator. The obtained small-sized microbeads (~300 μm) were exposed to a treatment medium containing SCB, composed of varied concentrations of sodium citrate (1.10-1.57 mM), sodium chloride (3.00-4.29 mM), and ethylenediaminetetraacetic acid (0.60-0.86 mM) to partially degrade their crosslinked structure for 3 days, followed by culture in a normal medium until day 21. Scanning electron microscope micrographs demonstrated a loose hydrogel network with an enhanced pore size in the SCB-treated microbeads. Increasing the concentration of SCB in the treatment medium reduced the calcium content of the microbeads via a Na⁺ /Ca²⁺ exchange process and improved the water absorption of the microbeads, resulting in a higher swelling ratio. All the tested SCB concentrations were non-cytotoxic. Increases in aggrecan and type II collagen gene expression and their corresponding extracellular matrix accumulation, glycosaminoglycans, and type II collagen were vividly detected in the TGF-β3-containing microbeads with increasing SCB concentrations in the treatment medium. Our findings highlighted that the combination of SCB treatment and TGF-β3 incorporation in the chondrocyte-laden microbeads is a promising strategy for enhancing cartilage regeneration, which may contribute to a versatile application in cell delivery and tissue engineering.

Embedded 3D printing of dilute particle suspensions into dense complex tissue fibers using shear thinning xanthan baths

In order to fabricate functional organoids and microtissues, a high cell density is generally required. As such, the placement of cell suspensions in molds or microwells to allow for cell concentration by sedimentation is the current standard for the production of organoids and microtissues. Even though molds offer some level of control over the shape of the resulting microtissue, this control is limited as microtissues tend to compact towards a sphere after sedimentation of the cells. 3D bioprinting on the other hand offers complete control over the shape of the resulting structure. Even though the printing of dense cell suspensions in the ink has been reported, extruding dense cellular suspensions is challenging and generally results in high shear stresses on the cells and a poor shape fidelity of the print. As such, additional materials such as hydrogels are added in the bioink to limit shear stresses, and to improve shape fidelity and resolution. The maximum cell concentration that can be incorporated in a hydrogel-based ink before the ink's rheological properties are compromised, is significantly lower than the concentration in a tissue equivalent. Additionally, the hydrogel components often interfere with cellular self-assembly processes. To circumvent these limitations, we report a simple and inexpensive xanthan bath based embedded printing method to 3D print dense functional linear tissues using dilute particle suspensions consisting of cells, spheroids, hydrogel beads, or combinations thereof. Using this method, we demonstrated the self-organization of functional cardiac tissue fibers with a layer of epicardial cells surrounding a body of cardiomyocytes.

Investigating the effect of graphene oxide in chitosan/alginate-based foams on the release and antifungal activity of clotrimazole in vitro

Polyelectrolyte complexes (PECs) have been used as the matrix of solid foams for drug delivery. This study aimed at investigating the effect of graphene oxide (GO) and the composition of excipients in chitosan/alginate-based buccal foams on the clotrimazole release and antifungal activities. The investigation has been focused on the interactions of the drug with excipients in the foams, and the changes of ionization degree upon exposure to various media are discussed. The solid foams were prepared by mixing the excipients and clotrimazole via probe sonication, followed by a freeze-drying method. The pH values of the formulations were measured during the foam preparation process to estimate the ionization degree of clotrimazole and the other excipients. The foam matrix was the PECs between the cationic chitosan and anionic alginate. The mechanical strength of clotrimazole-loaded foams was lower than that of drug-free foams due to the positively charged clotrimazole interacting with the anionic alginate and interfering the PECs between chitosan and alginate. Addition of GO in the clotrimazole-loaded matrix made the foams mechanically stronger and contributed to a faster release of clotrimazole from the buccal foams by disrupting the electrostatic interactions between alginate and clotrimazole. However, addition of 1 wt% GO in the formulations didn't affect the antifungal activity of clotrimazole-loaded foams significantly. A lower amount GO in the formulation may be required for enhancing the antifungal effect, which should be further investigated in future.

Advancements in the Delivery of Growth Factors and Cytokines for the Treatment of Cutaneous Wound Indications

Significance: Wound healing involves the phasic production of growth factors (GFs) and cytokines to progress an acute wound to a resolved scar. Dysregulation of these proteins contributes to both wound chronicity and excessive scarring. Direct supplementation of GFs and cytokines for treatment of healing and scarring complications has, however, been disappointing. Failings likely relate to an inability to deliver recombinant proteins at physiologically relevant levels to an environment conducive to healing. Recent Advances: Inspired by the extracellular matrix, natural biomaterials have been developed that resemble human skin, and are capable of delivering bioactives. Hybrid biomaterials made using multiple polymers, fabrication methods, and proteins are proving efficacious in animal models of acute and impaired wound healing. Critical Issues: For clinical translation, these delivery systems must be tailored for specific wound indications and the correct phase of healing. GFs and cytokines must be delivered in a controlled manner that will target specific healing or scarring impairments. Preclinical assessment in clinically relevant animal models of impaired or excessive healing is critical. Future Directions: Clinical success will likely depend on the GF or cytokine selected, their compatibility with the chosen biomaterial(s), degradation rate of the fabricated system, and the degree of control over release kinetics. Further testing is essential to assess which wound indications are most suited to specific delivery systems and to prove whether they provide superior efficacy over direct protein therapies.

Complexation of CXCL12, FGF-2 and VEGF with Heparin Modulates the Protein Release from Alginate Microbeads

Long-term delivery of growth factors and immunomodulatory agents is highly required to support the integrity of tissue in engineering constructs, e.g., formation of vasculature, and to minimize immune response in a recipient. However, for proteins with a net positive charge at the physiological pH, controlled delivery from negatively charged alginate (Alg) platforms is challenging due to electrostatic interactions that can hamper the protein release. In order to regulate such interactions between proteins and the Alg matrix, we propose to complex proteins of interest in this study - CXCL12, FGF-2, VEGF - with polyanionic heparin prior to their encapsulation into Alg microbeads of high content of α-L-guluronic acid units (high-G). This strategy effectively reduced protein interactions with Alg (as shown by model ITC and SPR experiments) and, depending on the protein type, afforded control over the protein release for at least one month. The released proteins retained their in vitro bioactivity: CXCL12 stimulated the migration of Jurkat cells, and FGF-2 and VEGF induced proliferation and maturation of HUVECs. The presence of heparin also intensified protein biological efficiency. The proposed approach for encapsulation of proteins with a positive net charge into high-G Alg hydrogels is promising for controlled long-term protein delivery under in vivo conditions.

Sustained Release of Bone Morphogenetic Protein-2 through Alginate Microbeads Enhances Bone Regeneration in Rabbit Tibial Metaphyseal Defect Model

Bone morphogenetic protein-2 (BMP-2) is widely used to enhance bone regeneration. However, because of its short half-life and rapid disappearance, large amounts of BMP-2 are needed, leading to unintended side effects. In this study, BMP-2-encapsulated alginate microbeads (AM) were used to enhance bone regeneration. Enzyme-linked immunosorbent assay confirmed the sustained release of BMP-2 from AM. Vascular endothelial growth factor (VEGF)-adsorbing aptamer-conjugated hydroxyapatite (Apt-HA) was used for osteoconduction and dual delivery of VEGF and BMP-2. For in vivo bone regeneration evaluation, the grafts (1) Apt-HA + phosphate-buffered saline (PBS), (2) Apt-HA + AM without BMP-2, (3) Apt-HA + BMP-2, and (4) Apt-HA + AM encapsulated with BMP-2 were implanted into rabbit tibial metaphyseal defects. After four weeks, micro-computed tomography (CT), histological, and histomorphometric analyses were performed to evaluate bone regeneration. The Apt-HA + AM with BMP-2 group revealed a significantly higher new bone volume and bone volume/total volume (BV/TV) in both cortical and trabecular bone than the others. Furthermore, as evaluated by histomorphometric analysis, BMP-2 AM exhibited a significantly higher bone formation area than the others, indicating that AM could be used to efficiently deliver BMP-2 through sustained release. Moreover, the combined application of BMP-2-encapsulated Apt-HA + AM may effectively promote bone regeneration.

Property modelling of lysozyme-crosslinker-alginate complexes using latent variable methods

Statistical methods were used to provide insight into a polymer complex system composed of lysozyme and alginate to quantify the effects of such parameters as pH, and ionic composition of the mixing solution on the properties of the complexes including composition, particle diameter, and zeta potential. Various crosslinkers (calcium, barium, iron[III], and bovine serum albumin), were used with lysozyme for complex formation to investigate the effect of crosslinker charge density on protein release kinetics, modelled using ktⁿ . Multivariate statistical analysis showed that the kinetic parameters associated with the release were, not surprisingly highly dependent on the ionic strength of the release media, with higher ionic strength leading to faster release. The release parameter k was also shown to depend on the protein properties (size, ionic strength) while n was slightly, but not statistically dependent on the charge density of the crosslinker demonstrating that the nature of the crosslinker had minimal impact on drug release. The multivariate statistical has the potential to be used for optimization of the complexes and prediction of physical properties and degradation rates.

A co-delivery platform for synergistic promotion of angiogenesis based on biodegradable, therapeutic and self-reporting luminescent porous silicon microparticles

Insufficient angiogenesis happened in body defects such as ulceration, coronary heart disease, and chronic wounds constitutes a major challenge in tissue regeneration engineering. Owing to the poor bioactivity and maintenance of pro-angiogenic cells and factors during transplantation, new bioactive materials to tackle the barrier are highly desirable. Herein, we demonstrate a co-delivery platform for synergistic promotion of angiogenesis based on biodegradable, therapeutic, and self-reporting luminescent porous silicon (PSi) microparticles. The biodegradable and biocompatible PSi microparticles could quickly release therapeutic Si ions, which is bioactive to promote cell migration, tube formation, and angiogenic gene expression in vitro. To construct a highly efficient angiogenesis treatment platform, vascular endothelial growth factor (VEGF) was electrostatically adsorbed by PSi microparticles for effective drug loading and delivery. The dual therapeutic components (Si ions and VEGF) could release with the dissolution of Si skeleton, accompanying by the decay of photoluminescence (PL) intensity and blue shift of the maximum PL wavelength. Therefore, real-time drug release could be self-reported and assessed with the two-dimensional PL signal. The co-delivery of Si ions and VEGF displayed synergistic effect and highly efficient angiogenesis, which was evidenced by the enhancement of endothelial cell migration and tube formation in vitro with approximately 1.5-5 times higher than control. The blood vessel formation in vivo was also significantly improved as shown by the chick chorioallantoic membrane (CAM) model, in which the total length, size and junctions exhibited 2.1 ± 0.4, 4 ± 0.4, and 3.9 ± 0.3 times in comparison to control, respectively. The PSi and VEGF co-delivery system display great potential in tissue engineering as a biodegradable and self-reporting theranostic platform to promote angiogenesis.

Coaxial Alginate Hydrogels: From Self-Assembled 3D Cellular Constructs to Long-Term Storage

Alginate as a versatile naturally occurring biomaterial has found widespread use in the biomedical field due to its unique features such as biocompatibility and biodegradability. The ability of its semipermeable hydrogels to provide a favourable microenvironment for clinically relevant cells made alginate encapsulation a leading technology for immunoisolation, 3D culture, cryopreservation as well as cell and drug delivery. The aim of this work is the evaluation of structural properties and swelling behaviour of the core-shell capsules for the encapsulation of multipotent stromal cells (MSCs), their 3D culture and cryopreservation using slow freezing. The cells were encapsulated in core-shell capsules using coaxial electrospraying, cultured for 35 days and cryopreserved. Cell viability, metabolic activity and cell-cell interactions were analysed. Cryopreservation of MSCs-laden core-shell capsules was performed according to parameters pre-selected on cell-free capsules. The results suggest that core-shell capsules produced from the low viscosity high-G alginate are superior to high-M ones in terms of stability during in vitro culture, as well as to solid beads in terms of promoting formation of viable self-assembled cellular structures and maintenance of MSCs functionality on a long-term basis. The application of 0.3 M sucrose demonstrated a beneficial effect on the integrity of capsules and viability of formed 3D cell assemblies, as compared to 10% dimethyl sulfoxide (DMSO) alone. The proposed workflow from the preparation of core-shell capsules with self-assembled cellular structures to the cryopreservation appears to be a promising strategy for their off-the-shelf availability.

Assessing the Angiogenic Efficacy of Pleiotrophin Released from Injectable Heparin-Alginate Gels

With this work, we design alginate-based hydrogels for therapeutically directing revascularization and repair processes in vivo. We immobilize pleiotrophin (PTN) in injectable hydrogel formulations as the target factor to stimulate proangiogenic responses in endothelial cells. The optimized heparin-alginate/chitosan hydrogels, produced by internal crosslinking with calcium carbonate, show good biocompatibility and injectability and allow controlling the release of immobilized proteins in the subcutaneous tissue over a period of 7 days. In vitro assays, performed with translational human induced pluripotent stem cell-derived endothelial cells, and the in vivo Matrigel plug assay are conducted to demonstrate the angiogenic effects of PTN on endothelial cells. Our results indicate that PTN stimulates endothelial cell morphogenesis in vitro and the migration of endothelial cells and macrophages as soon as 4 days after injections of the developed hydrogels, promoting the formation of structures similar to the healthy granulation tissue, which is an indicator of healing in ischemic wounds. These studies provide the rationale for further investigating this novel therapeutic for pursuing increased vascular density for efficient regeneration of ischemic tissues, by leveraging the host endothelial cell population to initiate angiogenic and reparative processes in vivo. Impact statement Localized, sustained, and controlled delivery of angiogenic factors is crucial for enabling the formation of novel vascular networks in ischemic tissues. This study describes the development of an injectable heparin-alginate/collagen hydrogel for controlling the in vivo release and bioactivity of pleiotrophin (PTN), a heparin-binding factor with significant angiogenic activity. We demonstrate that PTN promotes angiogenesis in an in vitro model of hypoxia and in preclinical subcutaneous models. These results advance our understanding of PTN function in guiding therapeutic angiogenesis and are critical to inform the development of novel translational strategies for ischemic tissue repair and regeneration.

A Novel Alginate-Based Delivery System for the Prevention and Treatment of Pressure-Overload Induced Heart Failure

Background: α-CGRP (alpha-calcitonin gene related peptide) is a cardioprotective neuropeptide. Our recent study demonstrated that the administration of native α-CGRP, using osmotic mini-pumps, protected against transverse aortic constriction (TAC) pressure-induced heart failure in mice. However, the short half-life of peptides and the non-applicability of osmotic pumps in humans limits the use of α-CGRP as a therapeutic agent for heart failure (HF). Here, we sought to comprehensively study a novel α-CGRP delivery system using alginate microcapsules to determine its bioavailability in vivo and to test for cardioprotective effects in HF mice.

Methods: Native α-CGRP filled alginate microcapsules (200 µm diameter) were prepared using an electrospray method. The prepared alginate-α-CGRP microcapsules were incubated with rat cardiac H9c2 cells, mouse cardiac HL-1 cells, and human umbilical vein endothelial cells (HUVECs), and the cytotoxicity of the alginate-α-CGRP microcapsules was measured by a trypan-blue cell viability assay and a calcium dye fluorescent based assay. The efficacy of the alginate-α-CGRP microcapsules was tested in a TAC-pressure overload mouse model of heart failure. Male C57BL6 mice were divided into four groups: sham, sham-alginate-α-CGRP, TAC-only, and TAC-alginate-α-CGRP, and the TAC procedure was performed in the TAC-only and TAC-alginate-α-CGRP groups of mice to induce pressure-overload heart failure. After 2 or 15 days post-TAC, alginate-α-CGRP microcapsules (containing an α-CGRP dose of 6 mg/kg/mouse) were administered subcutaneously on alternate days, for 28 days, and echocardiography was performed weekly. After 28 days of peptide delivery, the mice were sacrificed and their hearts were collected for histological and biochemical analyses.

Results: Our in vitro cell culture assays showed that alginate-α-CGRP microcapsules did not affect the viability of the cell lines tested. The alginate-α-CGRP microcapsules released their peptides for an extended period of time. Our echocardiography, biochemical, and histology data from HF mice demonstrated that the administration of alginate-α-CGRP microcapsules significantly improved all cardiac parameters examined in TAC-mice. When compared to sham mice, TAC significantly decreased cardiac functions (as determined by fraction shortening and ejection fraction) and markedly increased heart and lung weight, left ventricle (LV) cardiac cell size, cardiac apoptosis, and oxidative stress. In contrast, the administration of alginate-α-CGRP microcapsules significantly attenuated the increased heart and lung weight, LV cardiac cell size, apoptosis, and oxidative stress in TAC mice.

Conclusion: Our results demonstrate that the encapsulation of α-CGRP in an alginate polymer is an effective strategy to improve peptide bioavailability in plasma and increase the duration of the therapeutic effect of the peptide throughout the treatment period. Furthermore, alginate mediates α-CGRP delivery, either prior to the onset or after the initiation of the symptom progression of pressure-overload, improves cardiac function, and protects hearts against pressure-induced HF.

Hyaluronic Acid and Poly-l-Lysine Layers on Calcium Alginate Microspheres to Modulate the Release of Encapsulated FITC-Dextran

Alginate solutions crosslink into microspheres in calcium alginate, enabling the encapsulation and subsequent release of biological macromolecules and drugs. However, release from calcium alginate into PBS is relatively fast because it will decrosslink the gel relatively quickly. In this research, FITC-dextran (MW 10 kDa) was encapsulated in 2% (w/v) calcium alginate microspheres by electrospraying. The resulting microspheres (diameter = 247 ± 13 μm) were then layered with thin polyelectrolyte films of hyaluronic acid (HA) and poly-l-lysine (PLL) to attempt to slow the diffusion of FITC-dextran out of the microspheres and the coating parameters were modified to modulate diffusion and release. Increasing the concentration of FITC-dextran encapsulated in the microspheres resulted in an increase in its release over time into PBS. Crosslinking PLL/HA layers on the microspheres did not decrease the in vitro release rates of encapsulated FITC-dextran into PBS. Increasing the number of layers on the microspheres from 3 to 5 layers significantly decreased the amount of encapsulated FITC-dextran released. However, increasing the number of layers to 7 did not further sustain the release of FITC-dextran, likely because these microspheres collapsed to a smaller size during the coating procedure, resulting in release controlled by both diffusion and swelling. Multiple layers of PLL and HA provided a robust mechanism to sustain and control release of large molecules from calcium alginate.

Rheological Investigation of Thermoresponsive Alginate-Methylcellulose Gels for Epidermal Growth Factor Formulation

Epidermal growth factors (EGF) serve as promising candidates for skin regeneration and rejuvenation products, but their instability hinders them from widespread use. Protective immobilization and directed release can be achieved through implementing a hydrogel delivery system. Alginate and methylcellulose are both natural polymers offering biocompatibility and environmental sensitivity. This blended gel system was investigated rheologically to understand its performance in topical applications. Alginate and methylcellulose were found to form a synergistic gel system that resulted in superior viscosity and thermoresponsiveness compared to the individual components. Increasing methylcellulose concentration directly enhanced gel elasticity, and higher viscosities provided better thermal protection of EGF. The addition of EGF at 3.33 mg/mL resulted in a decrease of viscosity but an increase in viscoelastic modulus. EGF concentration also played a large role in shear viscosity and thermoresponsiveness of the ternary system. An alginate-methylcellulose system presents promising rheological tunability, which may provide EGF thermal protection in a topical delivery format.

Engineered biomaterial strategies for controlling growth factors in tissue engineering

Growth factors are multi-functional signaling molecules that coordinate multi-stage process of wound healing. During wound healing, growth factors are transmitted to wound environment in a positive and physiologically related way, therefore, there is a broad prospect for studying the mediated healing process through growth factors. However, growth factors (GFs) themselves have disadvantages of instability, short life, rapid inactivation of physiological conditions, low safety and easy degradation, which hinder the clinical use of GFs. Rapid development of delivery strategies for GFs has been trying to solve the instability and insecurity of GFs. Particularly, in recent years, GFs delivered by scaffolds based on biomaterials have become a hotspot in this filed. This review introduces various delivery strategies for growth factors based on new biodegradable materials, especially polysaccharides, which could provide guidance for the development of the delivery strategies for growth factors in clinic.

Immobilization of Growth Factors for Cell Therapy Manufacturing

Cell therapy products exhibit great therapeutic potential but come with a deterring price tag partly caused by their costly manufacturing processes. The development of strategies that lead to cost-effective cell production is key to expand the reach of cell therapies. Growth factors are critical culture media components required for the maintenance and differentiation of cells in culture and are widely employed in cell therapy manufacturing. However, they are expensive, and their common use in soluble form is often associated with decreased stability and bioactivity. Immobilization has emerged as a possible strategy to optimize growth factor use in cell culture. To date, several immobilization techniques have been reported for attaching growth factors onto a variety of biomaterials, but these have been focused on tissue engineering. This review briefly summarizes the current landscape of cell therapy manufacturing, before describing the types of chemistry that can be used to immobilize growth factors for cell culture. Emphasis is placed to identify strategies that could reduce growth factor usage and enhance bioactivity. Finally, we describe a case study for stem cell factor.

Research on alginate-polyacrylamide enhanced amnion hydrogel, a potential vascular substitute material

Although traditional synthetic vascular grafts have good mechanical stability, stenosis and even thrombus can be easily caused at the beginning of transplantation due to the material's procoagulant and low cell adhesion rate. In order to address these problems, by combining acellular amnion gel and polyacrylamide-alginate gel, we gained a composite hydrogel with high elasticity, mechanical stability, high bioactivity and low swelling ratio. The results showed that the composite gel had excellent mechanical strength, resistance to enzymatic degradation and anti-calcification ability. Also, it could significantly inhibit the adhesion, aggregation and activation of platelet and hemolysis. What is more, this composite hydrogel could significantly promote the adhesion and proliferation of ECs, as well as inducing the migration of ECs to the surface of the hydrogel. It could also stimulate the secretion of NO and PGI₂ from seeded HUVECs, which were important factors involved in vascular remodelling and repair. All the results indicated that prepared AlgSr/PAM-AM hydrogel was an excellent biomaterial with properties for potential use in vascular repair.

Enhanced Biocompatibility of Multi-Layered, 3D Bio-Printed Artificial Vessels Composed of Autologous Mesenchymal Stem Cells

Artificial vessels capable of long-term patency are essential clinical tools in vascular surgery that involves small vessels. On-going attempts to develop artificial vessels that complements restenosis have not been entirely successful. Here, we report on the fabrication of small-sized artificial vessels using a three-dimensional bio-printer. The fabrication employed biodegradable polycaprolactone and autologous MSCs harvested from the bone-marrow of canines. The MSCs were cultured and differentiated into endothelial-like cells. After confirming differentiation, artificial vessels comprising three-layers were constructed and implanted into the arteries of canines. The autologous MSCs printed on artificial vessels (cell-derived group) maintained a 64.3% patency (9 of 14 grafts) compared with artificial vessels without cells (control group, 54.5% patency (6 of 11 grafts)). The cell-derived vessels (61.9 cells/mm² ± 14.3) had more endothelial cells on their inner surfaces than the control vessels (21 cells/mm² ± 11.3). Moreover, the control vessels showed acute inflammation on the porous structures of the implanted artificial vessels, whereas the cell-derived vessels exhibited fibrinous clots with little to no inflammation. We concluded that the minimal rejection of these artificial vessels by the immune system was due to the use of autologous MSCs. We anticipate that this study will be of value in the field of tissue-engineering in clinical practice.

Orthogonal test design for the optimization of superparamagnetic chitosan plasmid gelatin microspheres that promote vascularization of artificial bone

The optimal conditions for the preparation of superparamagnetic chitosan plasmid (pReceiver‐M29‐VEGF165/DH5a) gelatin microspheres (SPCPGMs) were determined. Then, the performance of the SPCPGMs during neovascularization was evaluated in vivo. The SPCPGMs were prepared through a cross‐linking curing method and then filled into the hollow scaffold of an artificial bone. Neovascularization at the bone defect position was histologically examined in samples collected 2, 4, 6, and 8 weeks after the operation. The cellular magnetofection rate of superparamagnetic chitosan nanoparticles/plasmid (pReceiver‐M29‐VEGF165/DH5a) complexes reached 1–3% under static magnetic field (SMF). Meanwhile, the optimal conditions for SPCPGM fabrication were 20% Fe₃O₄ (w/v), 4 mg of plasmid, 5.3 mg of glutaraldehyde, and 500 rpm of emulsification rotate speed. Under oscillating magnetic fields (OMFs), 4–6 μg of plasmids was released daily for 21 days. Under the combined application of SMF and OMF, evident neovascularization occurred at the bone defect position 6 weeks after the operation. This result is expected to provide a new type of angiogenesis strategy for the research of bone tissue engineering.

Enhanced angiogenesis by the hyaluronic acid hydrogels immobilized with a VEGF mimetic peptide in a traumatic brain injury model in rats

Angiogenesis plays an important role in brain injury repair, which contributes to the reconstruction of regenerative neurovascular niche for promoting axonal regeneration in the lesion area. As a major component of developing brain extracellular matrix, hyaluronic acid (HA) has attracted more attention as a supporting matrix for brain repair. In the present study, HA-KLT hydrogel was developed via modifying HA with a VEGF mimetic peptide of KLT (KLTWQELYQLKYKGI). The characterization of the hydrogel shows that it could provide a porous, three-dimensional scaffold structure, which has a large specific surface area available for cell adhesion and interaction. Compared with the unmodified HA hydrogel, the HA-KLT hydrogel could effectively promote the attachment, spreading and proliferation of endothelial cells in vitro. Furthermore, the pro-angiogenic ability of hydrogels in vivo was evaluated by implanting them into the lesion cavities in the injured rat brain. Our results showed that the hydrogels could form a permissive interface with the host tissues at 4 weeks after implantation. Moreover, they could efficiently inhibit the formation of glial scars at the injured sites. The HA-KLT hydrogel could significantly increase the expression of endoglin/CD105 and promote the formation of blood vessels, suggesting that HA-KLT hydrogel promoted angiogenesis in vivo. Collectively, the HA-KLT hydrogel has the potential to repair brain defects by promoting angiogenesis and inhibiting the formation of glial-derived scar tissue.

Acellular and cellular approaches to improve diabetic wound healing

Chronic diabetic wounds represent a huge socioeconomic burden for both affected individuals and the entire healthcare system. Although the number of available treatment options as well as our understanding of wound healing mechanisms associated with diabetes has vastly improved over the past decades, there still remains a great need for additional therapeutic options. Tissue engineering and regenerative medicine approaches provide great advantages over conventional treatment options, which are mainly aimed at wound closure rather than addressing the underlying pathophysiology of diabetic wounds. Recent advances in biomaterials and stem cell research presented in this review provide novel ways to tackle different molecular and cellular culprits responsible for chronic and nonhealing wounds by delivering therapeutic agents in direct or indirect ways. Careful integration of different approaches presented in the current article could lead to the development of new therapeutic platforms that can address multiple pathophysiologic abnormalities and facilitate wound healing in patients with diabetes.

Chemically modified alginate bead matrix for efficient adsorptive recovery of trypsin from fresh bovine pancreas

The adsorption of commercial trypsin (Try) onto epichlorohydrin cross-linked alginate-guar gum matrix has been studied at equilibrium in batch and in fixed bed column. Experiments were conducted to study the effect of ionic strength, temperature and to obtain a thermodynamic characterization of the adsorption process. The resulting adsorption isotherm fitted the Hill equation. Experimental breakthrough curve profiles were compared with the theoretical breakthrough profiles obtained from the mathematical model, bed depth service time. At pH 5.0, 1.0 g hydrated matrix adsorbed 480.0 milligram of Try per gram of dried bed. The desorption process showed 80% of Try recovery in 50 mM phosphate buffer, pH 7.00-500 mM NaCl-20% propylene glycol. The obtained results were applied to an adsorption/washing/desorption process with fresh pancreas homogenate yielded 20% of recovery and 5.7 purification factor of Try. The matrix remained functional until the fifth cycle of repeated batch enzyme adsorption. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 2018.

Alginate Matrices for Protein Delivery – a Short Review

Growth factors are powerful molecules that regulate cellular growth, proliferation, healing, and cellular differentiation. A delivery matrix that incorporates growth factors with high loading efficiencies, controls their release, and maintains bioactivity would be a powerful tool for regenerative medicine. Alginate has several unique properties that make it an excellent platform for the delivery of proteins. Mild gelling conditions can minimize the risk of protein denaturation; moreover, alginate can serve as protection from degradation until protein release. Various modifications have been proposed to tune alginate binding and release proteins, simultaneously adjusting alginate degradability, mechanical stiffness, swelling, gelation properties and cell affinity. The primary objective of this article is to review the literature related to recent advances in the application of alginate matrices in protein delivery in regenerative medicine. A special emphasis is put on the relevance of delivery of growth factors and chemokine.

Enhanced cellular response elicited by addition of amniotic fluid to alginate hydrogel-electrospun silk fibroin fibers for potential wound dressing application

This study aimed to evaluate a novel bioactive wound dressing from alginate hydrogel-electrospun silk fibroin (SF) fibers with the ability to deliver amniotic fluid (AF) to the wound site. AF is highly enriched with multiple therapeutic agents that can promote cellular response and wound healing. In this study, electrospun SF fibers were first fabricated by electrospinning method and then combined with the alginate hydrogel (ALG) containing AF. Different dressings were made by changing the alginate to AF ratio. The scanning electron microscopy images revealed that SF fibers were fully covered with alginate hydrogel. In addition, the modulus of the dressing decreased by lowering ALG/AF ratios, while a reverse trend was observed for the elongation-at-break. In vitro AF release profiles indicated that an increase in the concentration of ALG leads to a reduction in the AF amount. Fibroblast culturing on the fabricated dressings demonstrated that cellular proliferation, spreading, and secretion of collagen enhanced with increasing AF. Taken together, our results provide a novel bioactive dressing with great potentials for speeding up the healing process in severe wounds.

A rapid method for determining protein diffusion through hydrogels for regenerative medicine applications

Hydrogels present versatile platforms for the encapsulation and delivery of proteins and cells for regenerative medicine applications. However, differences in hydrogel cross-linking density, polymer weight content, and affinity for proteins all contribute to diverse diffusion rates of proteins through hydrogel networks. Here, we describe a simple method to accurately measure protein diffusion through hydrogels, within a few hours and without the use of large amounts of protein. We tracked the diffusion of several proteins of varying molecular weights along the axial direction of capillary tubes filled with alginate, collagen, or poly(ethylene glycol) hydrogels. The rate of protein diffusion decreased with increasing molecular weight. A computational model of protein diffusion through capillary tubes was also created to predict and verify experimental protein diffusion coefficients. This in vitro capillary tube-based method of measuring protein diffusion represents a simple strategy to interrogate protein diffusion through natural and synthetic hydrogels and aid in the design of better biomaterial-based delivery vehicles that can effectively modulate protein release.

Three dimensional cell printing with sulfated alginate for improved bone morphogenetic protein-2 delivery and osteogenesis in bone tissue engineering

Three-dimensional (3D) cell printing is a unique technique that enables free-form fabrication of cell-laden hydrogel scaffolds with controllable features and interconnected pores for tissue engineering applications. To this end, bioink materials able to offer good printability and favorable cellular interaction are highly required. Herein, we synthesized alginate sulfate, which is a structural mimic of heparin that can strongly bind with growth factors to prolong their activities, and studied its feasibility for cell printing applications. Several bio-inks composed of alginate and alginate-sulfate were studied to characterize their material properties and their utilities in 3D printing. The inclusion of alginate-sulfate in bio-inks (alginate/alginate-sulfate) did not significantly influence their rheological properties and allowed for a good 3D printing processibility with distinct pores and features. Moreover, alginate/alginate-sulfate bio-inks exhibited an improved retention of bone morphogenetic protein 2 in 3D-printed scaffolds. Osteoblastic proliferation and differentiation in vitro were promoted by alginate/alginate-sulfate 3D-printed constructs with an optimal composition of 3% alginate and 2% alginate-sulfate. We envision that bio-inks displaying prolonged interactions with growth factors will be useful for tissue engineering applications including bone regeneration.

A novel dressing for the combined delivery of platelet lysate and vancomycin hydrochloride to chronic skin ulcers: Hyaluronic acid particles in alginate matrices

The aim of the present work was to develop a medication allowing for the combined delivery of platelet lysate (PL) and an anti-infective model drug, vancomycin hydrochloride (VCM), to chronic skin ulcers. A simple method was set up for the preparation of hyaluronic acid (HA) core-shell particles, loaded with PL and coated with calcium alginate, embedded in a VCM containing alginate matrix. Two different CaCl₂ concentrations were investigated to allow for HA/PL core-shell particle formation. The resulting dressings were characterized for mechanical and hydration properties and tested in vitro (on fibroblasts) and ex-vivo (on skin biopsies) for biological activity. They were found of sufficient mechanical strength to withstand packaging and handling stress and able to absorb a high amount of wound exudate and to form a protective gel on the lesion area. The CaCl₂ concentration used for shell formation did not affect VCM release from the alginate matrix, but strongly modified the release of PGFAB (chosen as representative of growth factors present in PL) from HA particles. In vitro and ex vivo tests provided sufficient proof of concept of the ability of dressings to improve skin ulcers healing.

Embryonic Stem Cell Sphere: A Controlled Method for Production of Mouse Embryonic Stem Cell Aggregates for Differentiation

Objectives

Embryonic stem cells (ESCs) are of significant interest as a renewable source of nonproliferating cells. Differentiation of ESCs is initiated by the formation of embryoid bodies (EBs). Standard methods of EB formation are limited in their production capacity, in any variations in EB size and formation of EBs through frequent passages. Here we have reported the utility of a microencapsulation technique for overcoming these limitations by mass production of mouse ESCs in alginate beads called ESC spheres.

Methods

The mouse ESCs were encapsulated in 1.2% alginate solution and cocultured on a feeder layer. The cells were evaluated by flow cytometry, in vitro differentiation, immunofluorescence, and reverse transcriptase polymerase chain reaction (RT-PCR).

Results

Analysis of encapsulated ESC spheres by flow cytometry showed similar percentages of Oct-4 and stage-specific embryonic antigen-1 (SSEA-1) expression in comparison with routine culture of ESCs. Moreover, the ESC spheres maintained a pluripotency potential which was comparable with ESCs cultured on feeder cells directly, as demonstrated by immunofluorescence and RT-PCR.

Conclusions

The results demonstrated that alginate encapsulation as a simple bioreactor, provides a scalable system for mass undifferentiated ESC sphere production with similar sizes and without the need for frequent passages for differentiation and clinical and pharmaceutical applications.

Coating Matters: Review on Colloidal Stability of Nanoparticles with Biocompatible Coatings in Biological Media, Living Cells and Organisms

Within the last two decades, the field of nanomedicine has not developed as successfully as has widely been hoped for. The main reason for this is the immense complexity of the biological systems, including the physico-chemical properties of the biological fluids as well as the biochemistry and the physiology of living systems. The nanoparticles' physicochemical properties are also highly important. These differ profoundly from those of freshly synthesized particles when applied in biological/living systems as recent research in this field reveals. The physico-chemical properties of nanoparticles are predefined by their structural and functional design (core and coating material) and are highly affected by their interaction with the environment (temperature, pH, salt, proteins, cells). Since the coating material is the first part of the particle to come in contact with the environment, it does not only provide biocompatibility, but also defines the behavior (e.g. colloidal stability) and the fate (degradation, excretion, accumulation) of nanoparticles in the living systems. Hence, the coating matters, particularly for a nanoparticle system for biomedical applications, which has to fulfill its task in the complex environment of biological fluids, cells and organisms. In this review, we evaluate the performance of different coating materials for nanoparticles concerning their ability to provide colloidal stability in biological media and living systems.

Platelet-rich fibrin-based matrices to improve angiogenesis in an in vitro co-culture model for bone tissue engineering

In the context of prevascularization strategies for tissue‐engineering purposes, co‐culture systems consisting of outgrowth endothelial cells (OECs) and primary osteoblasts (pOBs) have been established as a promising in vitro tool to study regeneration mechanisms and to identify factors that might positively influence repair processes such as wound healing or angiogenesis. The development of autologous injectable platelet‐rich fibrin (PRF), which can be generated from peripheral blood in a minimal invasive procedure, fulfils several requirements for clinically applicable cell‐based tissue‐engineering strategies. During this study, the established co‐culture system of OECs and pOBs was mixed with injectable PRF and was cultivated in vitro for 24 h or 7 days. The aim of this study was to analyse whether PRF might have a positive effect on wound healing processes and angiogenic activation of OECs in the co‐culture with regard to proinflammatory factors, adhesion molecules and proangiogenic growth factor expression. Histological cell detection revealed the formation of lumina and microvessel‐like structures in the PRF/co‐culture complexes after 7 days of complex cultivation. Interestingly, the angiogenic activation of OECs was accompanied by an upregulation of wound healing‐associated factors, as well as by a higher expression of the proangiogenic factor vascular endothelial growth factor, which was evaluated both on the mRNA level as well as on the protein level. Thus, PRF might positively influence wound healing processes, in particular angiogenesis, in the in vitro co‐culture, making autologous PRF‐based matrices a beneficial therapeutic tool for tissue‐engineering purposes by simply profiting from the PRF, which contains blood plasma, platelets and leukocytes.

VEGF-loaded microsphere patch for local protein delivery to the ischemic heart

BACKGROUND

Revascularization of the heart after myocardial infarction (MI) using growth factors delivered by hydrogel-based microspheres represents a promising therapeutic approach for cardiac regeneration. Microspheres have tuneable degradation properties and support the prolonged release of soluble factors. Cardiac patches provide mechanical restraint, preventing dilatation associated with ventricular remodelling.

METHODS

We combined these approaches and produced a compacted calcium-alginate microsphere patch, restrained by a chitosan sheet, to deliver vascular endothelial growth factor (VEGF) to the heart after myocardial injury in rats.

RESULTS

Microspheres had an average diameter of 3.2μm, were nonporous, and characterized by a smooth dimpled surface. Microsphere patches demonstrated prolonged in vitro release characteristics compared to non-compacted microspheres and VEGF supernatants obtained from patches maintained their bioactivity for the 5day duration of the study in vitro. In vivo, patches were assessed with magnetic resonance imaging following MI, and demonstrated 50% degradation 25.6days after implantation. Both VEGF^(-) and VEGF⁽⁺⁾ microsphere patch-treated hearts had better cardiac function than unpatched (chitosan sheet only) controls. However, VEGF⁽⁺⁾ microsphere-patched hearts had thicker scars characterized by higher capillary density in the border zone than did those treated with VEGF^(-) patches. VEGF was detected in the patches 4weeks post-implantation.

CONCLUSION

The condensed microsphere patch represents a new therapeutic platform for cytokine delivery and could be used as an adjuvant to current biomaterial and cell-based therapies to promote localized angiogenesis in the infarcted heart.

STATEMENT OF SIGNIFICANCE

Following a heart attack, a lack of blood flow to the heart results in loss of heart cells. Growth factors may facilitate growth of blood vessels and heart tissue repair and prevent the onset of heart failure. Determining a way to deliver these growth factors directly to the heart is vital. Here, we combined two biomaterial-based approaches to deliver vascular endothelial growth factor (VEGF) to rat hearts after heart attack: a microsphere for prolonged release of VEGF, and a cardiac patch for mechanical restraint to prevent heart dysfunction. The feasibility of this microsphere patch was demonstrated by surgically implanting it over the infarct region of the heart post-injury. VEGF-patched hearts had better blood vessel growth, tissue repair, and heart function.

Heme Iron Release from Alginate Beads at In Vitro Simulated Gastrointestinal Conditions

Heme iron (Fe) release from alginate beads at in vitro simulated gastrointestinal conditions for potential use as oral heme Fe supplement was studied. Five beads at different ratios of sodium alginate (SA)-to-spray-dried bovine blood cells (SDBC) with weight ratios of 1:1.25, 1:2.5, 1:5, 1:10, and 1:15 (w/w) were prepared. Release characteristics of these beads were investigated at in vitro simulated gastrointestinal conditions. Release media pH strongly influenced the controlled Fe release from the beads. The heme Fe-beads in simulated gastric fluid (pH 2) remained in a shrinkage state and Fe release was low: 25.8, 21.1, 11.6, 12.1, and 12.0 % for 1:1.25, 1:2.5, 1:5, 1:10, and 1:15 ratios, respectively. Proportion and amount of Fe released by 1:1.25 and 1:2.5 ratios was higher than the other ratios. The heme Fe-beads swelled and dissociated in simulated intestinal fluid (pH 6), releasing three-fourths of the Fe in 200 min. The morphology studies showed that Fe release followed formation of pores in the alginate matrix, generating erosion of the beads and complete disintegration after 75 and 200 min of gastric and intestinal incubation, respectively. These results indicate that heme Fe-beads may be useful for oral delivery of heme Fe supplement.

Encapsulation of anti-carbonic anhydrase IX antibody in hydrogel microspheres for tumor targeting

Encapsulation is a well-established method of biomaterial protection, controlled release, and efficient delivery. Here we evaluated encapsulation of monoclonal antibody M75 directed to tumor biomarker carbonic anhydrase IX (CA IX) into alginate microbeads (SA-beads) or microcapsules made of sodium alginate, cellulose sulfate, and poly(methylene-co-guanidine) (PMCG). M75 antibody release was quantified using ELISA and its binding properties were assessed by immunodetection methods. SA-beads showed rapid M75 antibody release in the first hour, followed by steady release during the whole experiment of 7 days. In contrast, the M75 release from PMCG capsules was gradual, reaching the maximum concentration on the 7th day. The release was more efficient at pH 6.8 compared to pH 7.4. The released antibody could recognize CA IX, and target the CA IX-positive cells in 3D spheroids. In conclusion, SA-beads and PMCG microcapsules can be considered as promising antibody reservoirs for targeting of cancer cells.

Formation of pH-responsive drug-delivery systems by electrospinning of vesicle-templated nanocapsule solutions

A novel nanofibrous membrane, which contains chitosan/sodium alginate nanocapsules constructed by vesicle systems, has been fabricated via an electrospinning process as a drug-delivery system.