Sulfated alginate microspheres associate with factor H and dampen the inflammatory cytokine response

Chemically modified seaweed polysaccharides: Improved functional and biological properties and prospective in food applications

Seaweed polysaccharides are natural biomacromolecules with unique physicochemical properties (e.g., good gelling, emulsifying, and film-forming properties) and diverse biological activities (e.g., anticoagulant, antioxidant, immunoregulatory, and antitumor effects). Furthermore, they are nontoxic, biocompatible and biodegradable, and abundant in resources. Therefore, they have been widely utilized in food, cosmetics, and pharmaceutical industries. However, their properties and bioactivities sometimes are not satisfactory for some purposes. Modification of polysaccharides can impart the amphiphilicity and new functions to the biopolymers and change the structure and conformation, thus effectively improving their functional properties and biological activities so as to meet the requirement for targeted applications. This review outlined the modification methods of representative red algae polysaccharides (carrageenan and agar), brown algae polysaccharides (fucoidan, alginate, and laminaran), and green algae polysaccharides (ulvan) that have potential food applications, including etherification, esterification, degradation, sulfation, phosphorylation, selenylation, and so on. The improved functional properties and bioactivities of the modified seaweed polysaccharides and their potential food applications are also summarized.

A pH/enzyme dual responsive PMB spatiotemporal release hydrogel promoting chronic wound repair

Suppressing persistent multidrug-resistant (MDR) bacterial infections and excessive inflammation is the key for treating chronic wounds. Therefore, developing a microenvironment-responsive material with good biodegradability, drug-loading, anti-infection, and anti-inflammatory properties is desired to boost the chronic wounds healing process; however, using ordinary assembly remains a defect. Herein, we propose a pH/enzyme dual-responsive polymyxin B (PMB) spatiotemporal-release hydrogel (GelMA/OSSA/PMB), namely, the amount of OSSA and PMB released from GelMA/OSSA/PMB was closely related the wound pH and the enzyme concentration changing. The GelMA/OSSA/PMB showed better biosafety than equivalent free PMB, owing to the controlled release of PMB, which helped kill planktonic bacteria and inhibit biofilm activity in vitro. In addition, the GelMA/OSSA/PMB exhibited excellent antibacterial and anti-inflammatory properties. A MDR Pseudomonas aeruginosa caused infection was effectively resolved by the GelMA/OSSA/PMB hydrogel in vivo, thereby significantly boosting wound closure during the inflammatory phase. Furthermore, GelMA/OSSA/PMB accelerated the sequential phases of wound repair.

Mesenchymal stromal cell spheroids in sulfated alginate enhance muscle regeneration

The therapeutic efficacy of mesenchymal stromal cells (MSCs) for tissue regeneration is critically linked to the potency of the complex mixture of growth factors, cytokines, exosomes, and other biological cues that they secrete. The duration of cell-based approaches is limited by rapid loss of cells upon implantation, motivating the need to prolong cell viability and extend the therapeutic influence of the secretome. We and others demonstrated that the secretome is upregulated when MSCs are formed into spheroids. Although the efficacy of the MSC secretome has been characterized in the literature, no studies have reported the therapeutic benefit of in situ sequestration of the secretome within a wound site using engineered biomaterials. We previously demonstrated the capacity of sulfated alginate hydrogels to sequester components of the MSC secretome for prolonged presentation in vitro, yet the efficacy of this platform has not been evaluated in vivo. In this study, we used sulfated alginate hydrogels loaded with MSC spheroids to aid in the regeneration of a rat muscle crush injury. We hypothesized that the use of sulfated alginate to bind therapeutically relevant growth factors from the MSC spheroid secretome would enhance muscle regeneration by recruiting host cells into the tissue site. The combination of sulfated alginate and MSC spheroids resulted in decreased collagen deposition, improved myogenic marker expression, and increased neuromuscular junctions 2 weeks after injury. These data indicate that MSC spheroids delivered in sulfated alginate represent a promising approach for decreased fibrosis and increased functional regeneration of muscle. STATEMENT OF SIGNIFICANCE: The therapeutic efficacy of mesenchymal stromal cells (MSCs) for tissue regeneration is attributed to the complex diversity of the secretome. Cell-based approaches are limited by rapid cell death, motivating the need to extend the availability of the secretome. We previously demonstrated that sulfated alginate hydrogels sequester components of the MSC secretome for prolonged presentation in vitro, yet no studies have reported the in situ sequestration of the secretome. Herein, we transplanted MSC spheroids in sulfated alginate hydrogels to promote muscle regeneration. MSC spheroids in sulfated alginate decreased collagen deposition, improved myogenic marker expression, and increased neuromuscular junctions. These data indicate that MSC spheroids delivered in sulfated alginate represent a promising approach for decreasing fibrosis and increasing functional muscle regeneration.

Sulfated Alginate Reduces Pericapsular Fibrotic Overgrowth on Encapsulated cGMP-Compliant hPSC-Hepatocytes in Mice

Intra-peritoneal placement of alginate encapsulated human induced pluripotent stem cell-derived hepatocytes (hPSC-Heps) represents a potential new bridging therapy for acute liver failure. One of the rate-limiting steps that needs to be overcome to make such a procedure more efficacious and safer is to reduce the accumulation of fibrotic tissue around the encapsulated cells to allow the free passage of relevant molecules in and out for metabolism. Novel chemical compositions of alginate afford the possibility of achieving this aim. We accordingly used sulfated alginate and demonstrated that this material reduced fibrotic overgrowth whilst not impeding the process of encapsulation nor cell function. Cumulatively, this suggests sulfated alginate could be a more suitable material to encapsulate hPSC-hepatocyte prior to human use.

Pericapsular fibrotic overgrowth mitigated in immunocompetent mice through microbead formulations based on sulfated or intermediate G alginates

Cell encapsulation in alginate microbeads is a promising approach to provide immune isolation in cell therapy without immunosuppression. However, the efficacy is hampered by pericapsular fibrotic overgrowth (PFO), causing encapsulated cells to lose function. Stability of the microbeads is important to maintain immune isolation in the long-term. Here, we report alginate microbeads with minimal PFO in immunocompetent C57BL/6JRj mice. Microbead formulations included either alginate with an intermediate (47 %) guluronate (G) content (IntG) or sulfated alginate (SA), gelled in Ca²⁺/Ba²⁺ or Sr²⁺. A screening panel of eleven microbead formulations were evaluated for PFO, yielding multiple promising microbeads. Two candidate formulations were evaluated for 112 days in vivo, exhibiting maintained stability and minimal PFO. Microbeads investigated in a human whole blood assay revealed low cytokine and complement responses, while SA microbeads activated coagulation. Protein deposition on microbeads explanted from mice investigated by confocal laser scanning microscopy (CLSM) showed minimal deposition of complement C3. Fibrinogen was positively associated with PFO, with a high deposition on microbeads of high G (68 %) alginate compared to IntG and SA microbeads. Overall, stable microbeads containing IntG or SA may serve in long-term therapeutic applications of cell encapsulation. STATEMENT OF SIGNIFICANCE: Alginate-based hydrogels in the format of micrometer size beads is a promising approach for the immunoisolation of cells in cell therapy. Clinical trials in type 1 diabetes have so far had limited success due to fibrotic responses that hinder the diffusion of nutrients and oxygen to the encapsulated cells, resulting in graft failure. In this study, minimal fibrotic response towards micrometer size alginate beads was achieved by chemical modification of alginate with sulfate groups. Also, the use of alginate with intermediate guluronic acid content resulted in minimally fibrotic microbeads. Fibrinogen deposition was revealed to be a good indicator of fibrosis. This study points to both new microsphere developments and novel insight in the mechanisms behind the fibrotic responses.

Immunomodulatory effects of polysaccharides from marine algae for treating cancer, infectious disease, and inflammation

A significant rise in the occurrence and severity of adverse reactions to several synthetic drugs has fueled considerable interest in natural product-based therapeutics. In humans and animals, polysaccharides from marine microalgae and seaweeds have immunomodulatory effects. In addition, these polysaccharides may possess antiviral, anticancer, hypoglycemic, anticoagulant, and antioxidant properties. During inflammatory diseases, such as autoimmune diseases and sepsis, immunosuppressive molecules can serve as therapeutic agents. Similarly, molecules that participate in immune activation can induce immune responses against cancer and infectious diseases. We aim to discuss the chemical composition of the algal polysaccharides, namely alginate, fucoidan, ascophyllan, and porphyran. We also summarize their applications in the treatment of cancer, infectious disease, and inflammation. Recent applications of nanoparticles that are based on algal polysaccharides for the treatment of cancer and inflammatory diseases have also been addressed. In conclusion, these applications of marine algal polysaccharides could provide novel therapeutic alternatives for several diseases.

Sulfated Alginate Hydrogels Prolong the Therapeutic Potential of MSC Spheroids by Sequestering the Secretome

Cell-based approaches to tissue repair suffer from rapid cell death upon implantation, limiting the window for therapeutic intervention. Despite robust lineage-specific differentiation potential in vitro, the function of transplanted mesenchymal stromal cells (MSCs) in vivo is largely attributed to their potent secretome comprising a variety of growth factors (GFs). Furthermore, GF secretion is markedly increased when MSCs are formed into spheroids. Native GFs are sequestered within the extracellular matrix (ECM) via sulfated glycosaminoglycans, increasing the potency of GF signaling compared to their unbound form. To address the critical need to prolong the efficacy of transplanted cells, alginate hydrogels are modified with sulfate groups to sequester endogenous heparin-binding GFs secreted by MSC spheroids. The influence of crosslinking method and alginate modification is assessed on mechanical properties, degradation rate, and degree of sulfate modification. Sulfated alginate hydrogels sequester a mixture of MSC-secreted endogenous biomolecules, thereby prolonging the therapeutic effect of MSC spheroids for tissue regeneration. GFs are sequestered for longer durations within sulfated hydrogels and retain their bioactivity to regulate endothelial cell tubulogenesis and myoblast infiltration. This platform has the potential to prolong the therapeutic benefit of the MSC secretome and serve as a valuable tool for investigating GF sequestration.

Heparin-modified alginate microspheres enhance neovessel formation in hiPSC-derived endothelial cells and heterocellular in vitro models by controlled release of vascular endothelial growth factor

A formidable challenge in regenerative medicine is the development of stable microvascular networks to restore adequate blood flow or to sustain graft viability and long-term function in implanted or ischemic tissues. In this work, we develop a biomimetic approach to increase the binding affinity of the extracellular matrix for the class of heparin-binding growth factors to localize and control the release of proangiogenic cues while maintaining their bioactivity. Sulfate and heparin moieties are covalently coupled to alginate, and alginate microspheres are produced and used as local delivery depots for vascular endothelial growth factor (VEGF). Release of VEGF from sulfate-alginate and heparin-alginate bulk hydrogels and microspheres was sustained over 14 days. In vitro evaluation with human induced pluripotent stem cell (hiPSC)-derived endothelial cells and aortic ring assay in a chemically defined hydrogel demonstrates development of primitive three-dimensional vessel-like networks in the presence of VEGF released from the chemically modified alginate microspheres. Furthermore, our results suggest that the sulfate groups available on the chemically modified alginate microspheres promote some new vessel formation even in VEGF-free samples. Based on this evidence, we conclude that sulfate- and heparin-alginate hydrogels are adaptive and bioactive delivery systems for revascularization therapy and translational vascular tissue engineering.

Cell microencapsulation technologies for sustained drug delivery: Latest advances in efficacy and biosafety

The development of cell microencapsulation systems began several decades ago. However, today few systems have been tested in clinical trials. For this reason, in the last years, researchers have directed efforts towards trying to solve some of the key aspects that still limit efficacy and biosafety, the two major criteria that must be satisfied to reach the clinical practice. Regarding the efficacy, which is closely related to biocompatibility, substantial improvements have been made, such as the purification or chemical modification of the alginates that normally form the microspheres. Each of the components that make up the microcapsules has been carefully selected to avoid toxicities that can damage the encapsulated cells or generate an immune response leading to pericapsular fibrosis. As for the biosafety, researchers have developed biological circuits capable of actively responding to the needs of the patients to precisely and accurately release the demanded drug dose. Furthermore, the structure of the devices has been subject of study to adequately protect the encapsulated cells and prevent their spread in the body. The objective of this review is to describe the latest advances made by scientist to improve the efficacy and biosafety of cell microencapsulation systems for sustained drug delivery, also highlighting those points that still need to be optimized.

Anti-Tumor Effects of Biomimetic Sulfated Glycosaminoglycans on Lung Adenocarcinoma Cells in 2D and 3D In Vitro Models

Lung cancer development relies on cell proliferation and migration, which in turn requires interaction with extracellular matrix (ECM) components such as glycosaminoglycans (GAGs). The mechanisms through which GAGs regulate cancer cell functions are not fully understood but they are, in part, mediated by controlled interactions with cytokines and growth factors (GFs). In order to mechanistically understand the effect of the degree of sulfation (DS) of GAGs on lung adenocarcinoma (LUAD) cells, we synthesized sulfated alginate (AlgSulf) as sulfated GAG mimics with DS = 0.0, 0.8, 2.0, and 2.7. Human (H1792) and mouse (MDA-F471) LUAD cell lines were treated with AlgSulf of various DSs at two concentrations 10 and 100 µg/mL and their anti-tumor properties were assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), trypan blue exclusion, and wound healing assays for 2D models and sphere formation assay for the 3D model. The proliferation and number of live MDA-F471 cells at the concentration of 100 µg/mL decreased significantly with the increase in the DS of biomimetic GAGs. In addition, the increase in the DS of biomimetic GAGs decreased cell migration (p < 0.001 for DS = 2.0 and 2.7 compared to control) and decreased the diameter and number of spheres formed (p < 0.001). The increased DS of biomimetic GAGs attenuated the expression of cancer stem cell (CSC)/progenitor markers in the 3D cultures. In conclusion, GAG-mimetic AlgSulf with increased DS exhibit enhanced anti-proliferative and migratory properties while also reducing growth of KRAS-mutant LUAD spheres in vitro. We suggest that these anti-tumor effects by GAG-mimetic AlgSulf are possibly due to differential binding to GFs and consequential decreased cell stemness. AlgSulf may be suitable for applications in cancer therapy after further in vivo validation.

Effects of Sulfated Fucans from Laminaria hyperborea Regarding VEGF Secretion, Cell Viability, and Oxidative Stress and Correlation with Molecular Weight

BACKGROUND

Sulfated fucans show interesting effects in the treatment of ocular diseases (e.g., age-related macular degeneration), depending on their chemical structure. Here, we compared three purified sulfated fucans from Laminaria hyperborea (LH) regarding cell viability, oxidative stress protection, and vascular endothelial growth factor (VEGF) secretion in ocular cells.

METHODS

High-molecular-weight sulfated fucan (Mw = 1548.6 kDa, Fuc1) was extracted with warm water and purified through ultrafiltration. Lower-molecular-weight samples (Mw = 499 kDa, Fuc2; 26.9 kDa, Fuc3) were obtained by mild acid hydrolysis of ultrapurified sulfated fucan and analyzed (SEC-MALS (Size-exclusion chromatography-Multi-Angle Light Scattering), ICP-MS, and GC). Concentrations between 1 and 100 µg/mL were tested. Cell viability was measured after 24 h (uveal melanoma cell line (OMM-1), retinal pigment epithelium (RPE) cell line ARPE-19, primary RPE cells) via MTT/MTS (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide/3-(4,5-Dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay. Oxidative stress protection was determined after 24 h (OMM-1, ARPE-19). VEGF secretion was analyzed via ELISA after three days (ARPE-19, RPE).

RESULTS

Fuc2 and Fuc3 were antiproliferative for OMM-1, but not for ARPE. Fuc1 protected OMM-1. VEGF secretion was lowered with all fucans except Fuc3 in ARPE-19 and RPE. The results suggest a correlation between molecular weight and biological activity, with efficiency increasing with size.

CONCLUSION

The LH sulfated fucan Fuc1 showed promising results regarding VEGF inhibition and protection, encouraging further medical research.

Polysaccharide matrices used in 3D in vitro cell culture systems

Polysaccharides comprise a diverse class of polymeric materials with a history of proven biocompatibility and continual use as biomaterials. Recent focus on new matrices appropriate for three-dimensional (3D) cell culture offers new opportunities to apply polysaccharides as extracellular matrix mimics. However, chemical and structural bases for specific cell-polysaccharide interactions essential for their utility as 3-D cell matrices are not well defined. This review describes how these naturally sourced biomaterials satisfy several key properties for current 3D cell culture needs and can also be synthetically modified or blended with additional components to tailor their cell engagement properties. Beyond their benign interactions with many cell types in cultures, their economical and high quality sourcing, optical clarity for ex situ analytical interrogation and in situ gelation represent important properties of these polymers for 3D cell culture applications. Continued diversification of their versatile glycan chemistry, new bio-synthetic sourcing strategies and elucidation of new cell-specific properties are attractive to expand the polysaccharide polymer utility for cell culture needs. Many 3D cell culture priorities are addressed with the portfolio of polysaccharide materials available and under development. This review provides a critical analysis of their properties, capabilities and challenges in 3D cell culture applications.

Sulfated Alginates as Heparin Analogues: A Review of Chemical and Functional Properties

Heparin is widely recognized for its potent anticoagulating effects, but has an additional wide range of biological properties due to its high negative charge and heterogeneous molecular structure. This heterogeneity has been one of the factors in motivating the exploration of functional analogues with a more predictable modification pattern and monosaccharide sequence, that can aid in elucidating structure-function relationships and further be structurally customized to fine-tune physical and biological properties toward novel therapeutic applications and biomaterials. Alginates have been of great interest in biomedicine due to their inherent biocompatibility, gentle gelling conditions, and structural versatility from chemo-enzymatic engineering, but display limited interactions with cells and biomolecules that are characteristic of heparin and the other glycosaminoglycans (GAGs) of the extracellular environment. Here, we review the chemistry and physical and biological properties of sulfated alginates as structural and functional heparin analogues, and discuss how they may be utilized in applications where the use of heparin and other sulfated GAGs is challenging and limited.

Anti-oxidant and immune-modulatory properties of sulfated alginate derivatives on human chondrocytes and macrophages

A sulfated biopolymer was found to have anti-oxidant and immunemodulatory properties. This class of materials has promise for treatment of joint disease.

Alginate: Current Use and Future Perspectives in Pharmaceutical and Biomedical Applications

Over the last decades, alginates, natural multifunctional polymers, have increasingly drawn attention as attractive compounds in the biomedical and pharmaceutical fields due to their unique physicochemical properties and versatile biological activities. The focus of the paper is to describe biological and pharmacological activity of alginates and to discuss the present use and future possibilities of alginates as a tool in drug formulation. The recent technological advancements with using alginates, issues related to alginates suitability as matrix for three-dimensional tissue cultures, adjuvants of antibiotics, and antiviral agents in cell transplantation in diabetes or neurodegenerative diseases treatment, and an update on the antimicrobial and antiviral therapy of the alginate based drugs are also highlighted.