Zwitterionically modified alginates mitigate cellular overgrowth for cell encapsulation

Atelocollagen supports three-dimensional culture of human induced pluripotent stem cells

As autologous induced pluripotent stem cell (iPSC) therapy requires a custom-made small-lot cell production line, and the cell production method differs significantly from the existing processes for producing allogeneic iPSC stocks for clinical use. Specifically, mass culture to produce stock is no longer necessary; instead, a series of operations from iPSC production to induction of differentiation of therapeutic cells must be performed continuously. A three-dimensional (3D) culture method using small, closed-cell manufacturing devices is suitable for autologous iPSC therapy. The use of such devices avoids the need to handle many patient-derived specimens in a single clean room; handling of cell cultures in an open system in a cell processing facility increases the risk of infection. In this study, atelocollagen beads were evaluated as a 3D biomaterial to assist 3D culture in the establishment, expansion culture, and induction of differentiation of iPSCs. It was found that iPSCs can be handled in a closed-cell device with the same ease as use of a two-dimensional (2D) culture when laminin-511 is added to the medium. In conclusion, atelocollagen beads enable 3D culture of iPSCs, and the quality of the obtained cells is at the same level as those derived from 2D culture.

Pancreatic islet cells in microfluidic-spun hydrogel microfibers for the treatment of diabetes

Islet transplantation has been developed as an effective cell therapy strategy to treat the progressive life-threatening disease Type 1 diabetes (T1DM). To mimic the natural islets and achieve immune isolation, hydrogel encapsulation of multiple islet cell types is the current endeavor. Here, we present a microfiber loading with pancreatic α and β cells by microfluidic spinning for diabetes treatment. Benefiting from microfluidic technology, the cells could be controllably and continuously loaded in the alginate and methacrylated hyaluronic acid (Alg-HAMA) microfiber and maintained their high bioactivity. The resultant microfiber could then hold the capacity of dual-mode glucose responsiveness attributed to the glucagon and insulin secreted by the encapsulated pancreatic α and β cells. After transplantation into the brown adipose tissue (BAT), these cell-laden microfibers showed successful blood glucose control in rodents and avoided the occurrence of hypoglycemia. These results conceived that the multicellular microfibers are expected to provide new insight into artificial islet preparation, diabetes treatment, and regenerative medicine as well as tissue engineering. STATEMENT OF SIGNIFICANCE: The microfibers were generated with a double network of alginate and methacrylated hyaluronic acid. The microfibers could simultaneously encapsulate pancreatic α and β cells and showed dual-mode glucose responsiveness. The cell-laden microfibers maintained a long-term hormone-releasing function in vivo. Cell-laden microfibers transplanted into diabetic mice could achieve glycemic control for 6 weeks.

Immunocompatible elastomer with increased resistance to the foreign body response

Polymeric elastomers are extensively employed to fabricate implantable medical devices. However, implantation of the elastomers can induce a strong immune rejection known as the foreign body response (FBR), diminishing their efficacy. Herein, we present a group of immunocompatible elastomers, termed easy-to-synthesize vinyl-based anti-FBR dense elastomers (EVADE). EVADE materials effectively suppress the inflammation and capsule formation in subcutaneous models of rodents and non-human primates for at least one year and two months, respectively. Implantation of EVADE materials significantly reduces the expression of inflammation-related proteins S100A8/A9 in adjacent tissues compared to polydimethylsiloxane. We also show that inhibition or knockout of S100A8/A9 leads to substantial attenuation of fibrosis in mice, suggesting a target for fibrosis inhibition. Continuous subcutaneous insulin infusion (CSII) catheters constructed from EVADE elastomers demonstrate significantly improved longevity and performance compared to commercial catheters. The EVADE materials reported here may enhance and extend function in various medical devices by resisting the local immune responses.

Zwitterion-Lubricated Hydrogel Microspheres Encapsulated with Metformin Ameliorate Age-Associated Osteoarthritis

Chondrocyte senescence and reduced lubrication play pivotal roles in the pathogenesis of age-related osteoarthritis (OA). In the present study, highly lubricated and drug-loaded hydrogel microspheres are designed and fabricated through the radical polymerization of sulfobetaine (SB)-modified hyaluronic acid methacrylate using microfluidic technology. The copolymer contains a large number of SB and carboxyl groups that can provide a high degree of lubrication through hydration and form electrostatic loading interactions with metformin (Met@SBHA), producing a high drug load for anti-chondrocyte senescence. Mechanical, tribological, and drug release analyses demonstrated enhanced lubricative properties and prolonged drug dissemination of the Met@SBHA microspheres. RNA sequencing (RNA-seq) analysis, network pharmacology, and in vitro assays revealed the extraordinary capacity of Met@SBHA to combat chondrocyte senescence. Additionally, inducible nitric oxide synthase (iNOS) has been identified as a promising protein modulated by Met in senescent chondrocytes, thereby exerting a significant influence on the iNOS/ONOO-/P53 pathway. Notably, the intra-articular administration of Met@SBHA in aged mice ameliorated cartilage senescence and OA pathogenesis. Based on the findings of this study, Met@SBHA emerges as an innovative and promising strategy in tackling age-related OA serving the dual function of enhancing joint lubrication and mitigating cartilage senescence.

Mechanically reinforced hydrogel vehicle delivering angiogenic factor for beta cell therapy

Type 1 diabetes mellitus (T1DM) is a chronic disease affecting millions worldwide. Insulin therapy is currently the golden standard for treating T1DM; however, it does not restore the normal glycaemic balance entirely, which increases the risk of secondary complications. Beta-cell therapy may be a possible way of curing T1DM and has already shown promising results in the clinic. However, low retention rates, poor cell survival, and limited therapeutic potential are ongoing challenges, thus increasing the need for better cell encapsulation devices. This study aimed to develop a mechanically reinforced vascular endothelial growth factor (VEGF)-delivering encapsulation device suitable for beta cell encapsulation and transplantation. Poly(l-lactide-co-ε-caprolactone) (PLCL)/gelatin methacryloyl (GelMA)/alginate coaxial nanofibres were produced using electrospinning and embedded in an alginate hydrogel. The encapsulation device was physically and biologically characterised and was found to be suitable for INS-1E beta cell encapsulation, vascularization, and transplantation in terms of its biocompatibility, porosity, swelling ratio and mechanical properties. Lastly, VEGF was incorporated into the hydrogel and the release kinetics and functional studies revealed a sustained release of bioactive VEGF for at least 14 days, making the modified alginate system a promising candidate for improving the beta cell survival after transplantation.

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.

An elastomer with in situ generated pure zwitterionic surfaces for fibrosis-resistant implants

Polymeric elastomers are widely utilized in implantable biomedical devices. Nevertheless, the implantation of these elastomers can provoke a robust foreign body response (FBR), leading to the rejection of foreign implants and consequently reducing their effectiveness in vivo. Building effective anti-FBR coatings on those implants remains challenging. Herein, we introduce a coating-free elastomer with superior immunocompatibility. A super-hydrophilic anti-fouling zwitterionic layer can be generated in situ on the surface of the elastomer through a simple chemical trigger. This elastomer can repel the adsorption of proteins, as well as the adhesion of cells, platelets, and diverse microbes. The elastomer elicited negligible inflammatory responses after subcutaneous implantation in rodents for 2 weeks. No apparent fibrotic capsule formation was observed surrounding the elastomer after 6 months in rodents. Continuous subcutaneous insulin infusion (CSII) catheters constructed from the elastomer demonstrated prolonged longevity and performance compared to commercial catheters, indicating its great potential for enhancing and extending the performance of various implantable biomedical devices by effectively attenuating local immune responses. STATEMENT OF SIGNIFICANCE: The foreign body response remains a significant challenge for implants. Complicated coating procedures are usually needed to construct anti-fibrotic coatings on implantable elastomers. Herein, a coating-free elastomer with superior immunocompatibility was achieved using a zwitterionic monomer derivative. A pure zwitterionic layer can be generated on the elastomer surface through a simple chemical trigger. This elastomer significantly reduces protein adsorption, cell and bacterial adhesion, and platelet activation, leading to minimal fibrotic capsule formation even after six months of subcutaneous implantation in rodents. CSII catheters constructed from the PQCBE-H elastomer demonstrated prolonged longevity and performance compared to commercial catheters, highlighting the significant potential of PQCBE-H elastomers for enhancing and extending the performance of various implantable biomedical devices.

Materials Strategies to Overcome the Foreign Body Response

The foreign body response (FBR) is an immune-mediated reaction that can occur with most biomaterials and biomedical devices. The FBR initiates a deterioration in the performance of implantable devices, representing a longstanding challenge that consistently hampers their optimal utilization. Over the last decade, significant strides are achieved based on either hydrogel design or surface modifications to mitigate the FBR. This review delves into recent material strategies aimed at mitigating the FBR. Further, the authors look forward to future novel anti-FBR materials from the perspective of clinical translation needs. Such prospective materials hold the potential to attenuate local immune responses, thereby significantly enhancing the overall performance of implantable devices.

Emerging Strategies for Beta Cell Encapsulation for Type 1 Diabetes Therapy

Diabetes is a prevalent chronic disease affecting millions of people globally. To address this health challenge, advanced beta cell therapy using biomaterials-based macroscale, microscale, and nanoscale encapsulation devices must tackle various obstacles. First, overcoming foreign body responses is a major focus of research. Strategies such as immunomodulatory materials and physical immunoshielding are investigated to reduce the immune response and improve the longevity of the encapsulated cells. Furthermore, oxygenating strategies, such as the use of oxygen-releasing biomaterials, are developed to improve oxygen diffusion and promote cell survival. Finally, yet importantly, promoting vascularization through the use of angiogenic growth factors and the incorporation of pre-vascularized materials are also explored to enhance nutrient and oxygen supply to the encapsulated cells. This review seeks to specifically highlight the emerging research strategies developed to overcome these challenges using micro and nanoscale biomaterial encapsulation devices. Continuously improving and refining these strategies make an advance toward realizing the improved therapeutic potential of the encapsulated beta cells.

Synergistic Effect of Multilayered Alginate/Poly(SBMA) Coatings on Marine Antifouling Property

Alginate (Alg) coatings have attracted attention as protective layers on solid surfaces for marine antifouling applications due to their strong water binding capability and environmentally friendly characteristics. However, the effectiveness of Alg coatings in preventing marine fouling diminishes upon interaction with divalent cations present in seawater. To address this issue, post-modification of the Alg coating is conducted. The carboxyl groups of Alg, which are susceptible sites for interaction with divalent cations, are conjugated with polymerization initiators through metal-mediated coordination bond formation. Subsequently, poly(sulfobetaine methacrylate) (poly(SBMA)) brushes are grown from the initiator-immobilized Alg coatings, resulting in the formation of multilayered Alg/poly(SBMA) coatings. In marine diatom adhesion assays using Amphora Coffeaeformis, multilayered Alg/poly(SBMA) coatings exhibited superior antifouling performance compared to single-layered Alg or poly(SBMA) coating controls.

Decoding the "Fingerprint" of Implant Materials: Insights into the Foreign Body Reaction

Foreign body reaction (FBR) is a prevalent yet often overlooked pathological phenomenon, particularly within the field of biomedical implantation. The presence of FBR poses a heavy burden on both the medical and socioeconomic systems. This review seeks to elucidate the protein "fingerprint" of implant materials, which is generated by the physiochemical properties of the implant materials themselves. In this review, the activity of macrophages, the formation of foreign body giant cells (FBGCs), and the development of fibrosis capsules in the context of FBR are introduced. Additionally, the relationship between various implant materials and FBR is elucidated in detail, as is an overview of the existing approaches and technologies employed to alleviate FBR. Finally, the significance of implant components (metallic materials and non-metallic materials), surface CHEMISTRY (charge and wettability), and physical characteristics (topography, roughness, and stiffness) in establishing the protein "fingerprint" of implant materials is also well documented. In conclusion, this review aims to emphasize the importance of FBR on implant materials and provides the current perspectives and approaches in developing implant materials with anti-FBR properties.

Emerging approaches for the development of artificial islets

The islet of Langerhans, functioning as a "mini organ", plays a vital role in regulating endocrine activities due to its intricate structure. Dysfunction in these islets is closely associated with the development of diabetes mellitus (DM). To offer valuable insights for DM research and treatment, various approaches have been proposed to create artificial islets or islet organoids with high similarity to natural islets, under the collaborative effort of biologists, clinical physicians, and biomedical engineers. This review investigates the design and fabrication of artificial islets considering both biological and tissue engineering aspects. It begins by examining the natural structures and functions of native islets and proceeds to analyze the protocols for generating islets from stem cells. The review also outlines various techniques used in crafting artificial islets, with a specific focus on hydrogel-based ones. Additionally, it provides a concise overview of the materials and devices employed in the clinical applications of artificial islets. Throughout, the primary goal is to develop artificial islets, thereby bridging the realms of developmental biology, clinical medicine, and tissue engineering.

In Situ Sprayed Exosome-Cross-Linked Gel as Artificial Lymph Nodes for Postoperative Glioblastoma Immunotherapy

One key challenge in postoperative glioblastoma immunotherapy is to guarantee a potent and durable T-cell response, which is restricted by the immunosuppressive microenvironment within the lymph nodes (LNs). Here, we develop an in situ sprayed exosome-cross-linked gel that acts as an artificial LN structure to directly activate the tumor-infiltrating T cells for prevention of glioma recurrence. Briefly, this gel is generated by a bio-orthogonal reaction between azide-modified chimeric exosomes and alkyne-modified alginate polymers. Particularly, these chimeric exosomes are generated from dendritic cell (DC)-tumor hybrid cells, allowing for direct and robust T-cell activation. The gel structure with chimeric exosomes as cross-linking points avoids the quick clearance by the immune system and thus prolongs the durability of antitumor T-cell immunity. Importantly, this exosome-containing immunotherapeutic gel provides chances for ameliorating functions of antigen-presenting cells (APCs) through accommodating different intracellular-acting adjuvants, such as stimulator of interferon genes (STING) agonists. This further enhances the antitumor T-cell response, resulting in the almost complete elimination of residual lesions after surgery. Our findings provide a promising strategy for postsurgical glioma immunotherapy that warrants further exploration in the clinical arena.

Advances and challenges of the cell-based therapies among diabetic patients

Diabetes mellitus is a significant global public health challenge, with a rising prevalence and associated morbidity and mortality. Cell therapy has evolved over time and holds great potential in diabetes treatment. In the present review, we discussed the recent progresses in cell-based therapies for diabetes that provides an overview of islet and stem cell transplantation technologies used in clinical settings, highlighting their strengths and limitations. We also discussed immunomodulatory strategies employed in cell therapies. Therefore, this review highlights key progresses that pave the way to design transformative treatments to improve the life quality among diabetic patients.

Macrophage Polarization Dynamics in Biomaterials: Implications for in Vitro Wound Healing

The interaction between biomaterials and the immune system plays a pivotal role in determining the success or failure of implantable devices. Macrophages, as key orchestrators of immune responses, exhibit diverse reactions that influence tissue integration or lead to implant failure. This study focuses on unraveling the intricate relationship between macrophage phenotypes and biomaterials, specifically hydrogels, by employing THP-1 cells as a model. Through a comprehensive investigation using polysaccharide, polymer, and protein-based hydrogels, our research sheds light on how the properties of hydrogels influence macrophage polarization. Phenotypic observations, biochemical assays, surface marker expression, and gene expression profiles collectively demonstrate the differential macrophage polarization abilities of polysaccharide-, polymer-, and protein-based hydrogels. Moreover, our indirect coculture studies reveal that hydrogels fostering M2 polarization exhibit exceptional wound-healing capabilities. These findings highlight the crucial role of the hydrogel microenvironment in adjusting macrophage polarization, offering a fresh avenue for refining biomaterials to bolster advantageous immune responses and improve tissue integration. This research contributes valuable insights for designing biomaterials with tailored properties that can guide macrophage behavior, ultimately improving the overall success of implantable devices.

Silicone cryogel skeletons enhance the survival and mechanical integrity of hydrogel-encapsulated cell therapies

The transplantation of engineered cells that secrete therapeutic proteins presents a promising method for addressing a range of chronic diseases. However, hydrogels used to encase and protect non-autologous cells from immune rejection often suffer from poor mechanical properties, insufficient oxygenation, and fibrotic encapsulation. Here, we introduce a composite encapsulation system comprising an oxygen-permeable silicone cryogel skeleton, a hydrogel matrix, and a fibrosis-resistant polymer coating. Cryogel skeletons enhance the fracture toughness of conventional alginate hydrogels by 23-fold and oxygen diffusion by 2.8-fold, effectively mitigating both implant fracture and hypoxia of encapsulated cells. Composite implants containing xenogeneic cells engineered to secrete erythropoietin significantly outperform unsupported alginate implants in therapeutic delivery over 8 weeks in immunocompetent mice. By improving mechanical resiliency and sustaining denser cell populations, silicone cryogel skeletons enable more durable and miniaturized therapeutic implants.

Poly(Glutamic Acid-Lysine) Hydrogels with Alternating Sequence Resist the Foreign Body Response in Rodents and Non-Human Primates

The foreign body response (FBR) to implanted biomaterials and biomedical devices can severely impede their functionality and even lead to failure. The discovery of effective anti-FBR materials remains a formidable challenge. Inspire by the enrichment of glutamic acid (E) and lysine (K) residues on human protein surfaces, a class of zwitterionic polypeptide (ZIP) hydrogels with alternating E and K sequences to mitigate the FBR is prepared. When subcutaneously implanted, the ZIP hydrogels caused minimal inflammation after 2 weeks and no obvious collagen capsulation after 6 months in mice. Importantly, these hydrogels effectively resisted the FBR in non-human primate models for at least 2 months. In addition, the enzymatic degradability of the gel can be controlled by adjusting the crosslinking degree or the optical isomerism of amino acid monomers. The long-term FBR resistance and controlled degradability of ZIP hydrogels open up new possibilities for a broad range of biomedical applications.

Medical, pharmaceutical, and nutritional applications of 3D-printing technology in diabetes

AIMS

Despite numerous studies covering the various features of three-dimensional printing (3D printing) technology, and its applications in food science and disease treatment, no study has yet been conducted to investigate applying 3D printing in diabetes. Therefore, the present study centers on the utilization and impact of 3D printing technology in relation to the nutritional, pharmaceutical, and medicinal facets of diabetes management. It highlights the latest advancements, and challenges in this field.

METHODS

In this review, the articles focusing on the application and effect of 3D printing technology on medical, pharmaceutical, and nutritional aspects of diabetes management were collected from different databases.

RESULT

High precision of 3D printing in the placement of cells led to accurate anatomic control, and the possibility of bio-printing pancreas and β-cells. Transdermal drug delivery via 3D-printed microneedle (MN) patches was beneficial for the management of diabetes disease. 3D printing supported personalized medicine for Diabetes Mellitus (DM). For instance, it made it possible for pharmaceutical companies to manufacture unique doses of medications for every diabetic patient. Moreover, 3D printing allowed the food industry to produce high-fiber and sugar-free products for the individuals with DM.

CONCLUSIONS

In summary, applying 3D printing technology for diabetes management is in its early stages, and needs to be matured and developed to be safely used for humans. However, its rapid progress in recent years showed a bright future for the treatment of diabetes.

Recent Advances in Alginate-Based Hydrogels for Cell Transplantation Applications

With its exceptional biocompatibility, alginate emerged as a highly promising biomaterial for a large range of applications in regenerative medicine. Whether in the form of microparticles, injectable hydrogels, rigid scaffolds, or bioinks, alginate provides a versatile platform for encapsulating cells and fostering an optimal environment to enhance cell viability. This review aims to highlight recent studies utilizing alginate in diverse formulations for cell transplantation, offering insights into its efficacy in treating various diseases and injuries within the field of regenerative medicine.

Ionically annealed zwitterionic microgels for bioprinting of cartilaginous constructs

Foreign body response (FBR) is a pervasive problem for biomaterials used in tissue engineering. Zwitterionic hydrogels have emerged as an effective solution to this problem, due to their ultra-low fouling properties, which enable them to effectively inhibit FBRin vivo. However, no versatile zwitterionic bioink that allows for high resolution extrusion bioprinting of tissue implants has thus far been reported. In this work, we introduce a simple, novel method for producing zwitterionic microgel bioink, using alginate methacrylate (AlgMA) as crosslinker and mechanical fragmentation as a microgel fabrication method. Photocrosslinked hydrogels made of zwitterionic carboxybetaine acrylamide (CBAA) and sulfobetaine methacrylate (SBMA) are mechanically fragmented through meshes with aperture diameters of 50 and 90µm to produce microgel bioink. The bioinks made with both microgel sizes showed excellent rheological properties and were used for high-resolution printing of objects with overhanging features without requiring a support structure or support bath. The AlgMA crosslinker has a dual role, allowing for both primary photocrosslinking of the bulk hydrogel as well as secondary ionic crosslinking of produced microgels, to quickly stabilize the printed construct in a calcium bath and to produce a microporous scaffold. Scaffolds showed ∼20% porosity, and they supported viability and chondrogenesis of encapsulated human primary chondrocytes. Finally, a meniscus model was bioprinted, to demonstrate the bioink's versatility at printing large, cell-laden constructs which are stable for furtherin vitroculture to promote cartilaginous tissue production. This easy and scalable strategy of producing zwitterionic microgel bioink for high resolution extrusion bioprinting allows for direct cell encapsulation in a microporous scaffold and has potential forin vivobiocompatibility due to the zwitterionic nature of the bioink.

Fibrous capsule-resistant, controllably degradable and functionalizable zwitterion-albumin hybrid hydrogels

Foreign body response (FBR) represents an immune-mediated cascade reaction capable of inducing the rejection of foreign implants, thereby compromising their in vivo performance. Pure zwitterionic hydrogels have demonstrated the ability to resist long-term FBR, owing to their outstanding antifouling capabilities. However, achieving such a robust anti-FBR effect necessitates stringent requirements concerning the purity of zwitterionic materials, which constrains their broader functional applications. Herein, we present a biocompatible, controllably degradable, and functionalizable zwitterion-albumin hybrid hydrogel. The zwitterionic hydrogel crosslinked with serum albumin exhibits controllable degradation and excels in preventing the adsorption of various proteins and adhesion of cells and bacteria. Moreover, the hydrogel significantly alleviates the host's FBR compared with PEG hydrogels and particularly outperforms PEG-based cross-linker crosslinked zwitterionic hydrogels in reducing collagen encapsulation when subcutaneously implanted into mice. The zwitterion-albumin hybrid hydrogel shows potential as a functionalizable anti-FBR material in the context of implantable materials and biomedical devices.

Inflammation-induced subcutaneous neovascularization for the long-term survival of encapsulated islets without immunosuppression

Cellular therapies for type-1 diabetes can leverage cell encapsulation to dispense with immunosuppression. However, encapsulated islet cells do not survive long, particularly when implanted in poorly vascularized subcutaneous sites. Here we show that the induction of neovascularization via temporary controlled inflammation through the implantation of a nylon catheter can be used to create a subcutaneous cavity that supports the transplantation and optimal function of a geometrically matching islet-encapsulation device consisting of a twisted nylon surgical thread coated with an islet-seeded alginate hydrogel. The neovascularized cavity led to the sustained reversal of diabetes, as we show in immunocompetent syngeneic, allogeneic and xenogeneic mouse models of diabetes, owing to increased oxygenation, physiological glucose responsiveness and islet survival, as indicated by a computational model of mass transport. The cavity also allowed for the in situ replacement of impaired devices, with prompt return to normoglycemia. Controlled inflammation-induced neovascularization is a scalable approach, as we show with a minipig model, and may facilitate the clinical translation of immunosuppression-free subcutaneous islet transplantation.

A composite capsule strategy to support longevity of microencapsulated pancreatic β cells

Pancreatic islet microencapsulation allows transplantation of insulin producing cells in absence of systemic immunosuppression, but graft survival is still limited. In vivo studies have demonstrated that many islet-cells die in the immediate period after transplantation. Here we test whether intracapsular inclusion of ECM components (collagen IV and RGD) with necrostatin-1 (Nec-1), as well as amino acids (AA) have protective effects on islet survival. Also, the inclusion of pectin was tested as it enhances the mitochondrial health of β-cells. To enhance the longevity of encapsulated islets, we studied the impact of the incorporation of the mentioned components into the alginate-based microcapsules in vitro. The efficacy of the different composite microcapsules on MIN6 β-cell or human islet-cell survival and function, as well as suppression of DAMP-induced immune activation, were determined. Finally, we examined the mitochondrial dynamic genes. This was done in the absence and presence of a cytokine cocktail. Here, we found that composite microcapsules of APENAA improved insulin secretion and enhanced the mitochondrial activity of β-cells. Under cytokine exposure, they prevented the cytokine-induced decrease of mitochondrial activity as well as viability till day 5. The rescuing effects of the composite capsules were accompanied by alleviated mitochondrial dynamic gene expression. The composite capsule strategy of APENAA might support the longevity of microencapsulated β-cells by lowering susceptibility to inflammatory stress. Our data demonstrate that combining strategies to support β-cells by changing the intracapsular microenvironment might be an effective way to preserve islet graft longevity in the immediate period after transplantation.

Injectable spontaneously formed asymmetric adhesive hydrogel with controllable removal for wound healing

Healing large-scale wounds has been a long-standing challenge in the field of biomedicine. Herein, we propose an injectable oxidated sodium alginate/gelatin/3,3'-dithiobis(propionic hydrazide)-aurum (Alg-CHO/gelatin/DTPH-Au) hydrogel filler with asymmetric adhesion ability and removability, which is formed by the Schiff-base reaction between aldehyde-based sodium alginate and multi-amino crosslinkers (gelatin and DTPH), combined with the coordination interaction between Au nanoparticles and disulfide bond of DTPH. Consequently, the prepared Alg-CHO/gelatin/DTPH-Au hydrogel exhibits high mechanical properties and injectable behaviors owing to its multiple-crosslinked interactions. Moreover, because various types of interaction bonding form on the contact side with the tissue, denser crosslinking of the upper layer relative to the lower layer occurs. Combined with the temperature difference between the upper and lower surfaces, this results in asymmetric adhesive properties. Owing to the photothermal effect, the reversible coordination interaction between Au nanoparticles and DTPH and the change in the triple helix structure of gelatin to a coil structure impart the filler-phased removability and antibacterial ability. The choice of all natural polymers also allows for favorable degradability of the wound filler and outstanding biocompatibility. Based on these features, this versatile wound filler can achieve a wide range of applications in the field of all-skin wound repair.

Antifouling Properties of Amine-Oxide-Containing Zwitterionic Polymers

Biofouling due to nonspecific proteins or cells on the material surfaces is a major challenge in a range of applications such as biosensors, medical devices, and implants. Even though poly(ethylene glycol) (PEG) has become the most widely used stealth material in medical and pharmaceutical products, the number of reported cases of PEG-triggered rare allergic responses continues to increase in the past decades. Herein, a new type of antifouling material poly(amine oxide) (PAO) has been evaluated as an alternative to overcome nonspecific foulant adsorption and impart comparable biocompatibility. Alkyl-substituted PAO containing diethyl, dibutyl, and dihexyl substituents are prepared, and their solution properties are studied. Photoreactive copolymers containing benzophenone as the photo-cross-linker are prepared by reversible addition-fragmentation chain-transfer polymerization and fully characterized by gel permeation chromatography and dynamic light scattering. Then, these water-soluble polymers are anchored onto a silicon wafer with the aid of UV irradiation. By evaluating the fouling resistance properties of these modified surfaces against various types of foulants, protein adsorption and bacterial attachment assays show that the cross-linked PAO-modified surface can efficiently inhibit biofouling. Furthermore, human blood cell adhesion experiments demonstrate that our PAO polymer could be used as a novel surface modifier for biomedical devices.

Natural Polysaccharide Delivery Platforms with Multiscale Structure Used for Cancer Chemoimmunotherapy

Chemoimmunotherapy is an effective cancer treatment method. Drugs are always combined and used in treating cancer. However, the characteristic of drugs varies, making it challenging to control their release kinetics utilizing delivery devices with a single microstructure. In this study, we attempted to uniformly size drugs of varying molecular weights and confine them in a compartment where immune cells may be recruited and moved freely. Dextran microgels were created as modular drug libraries to address the cryogel burst release of small molecule drugs. Then, modular drug libraries and granulocyte-macrophage colony-stimulating factor (GM-CSF) were integrated into cryogels for a combined treatment. Herein, alginate was zwitterion modified to avoid the immune reaction generated by the material. Because of its macroporous structure, the cryogel could be injected into the body, eliminating invasive surgical procedures. Results demonstrated that multiscale delivery platforms could improve the synergistic effect of various medications on tumor treatment.

An injectable and biodegradable zwitterionic gel for extending the longevity and performance of insulin infusion catheters

Continuous subcutaneous insulin infusion (CSII) is an essential insulin replacement therapy in the management of diabetes. However, the longevity of clinical CSII is limited by skin complications, by impaired insulin absorption and by occlusions associated with the subcutaneous insertion of CSII catheters, which require replacement and rotation of the insertion site every few days. Here we show that a biodegradable zwitterionic gel covering the tip end of commercial off-the-shelf CSII catheters fully resolves early skin irritations, extends the longevity of catheters and improves the rate of insulin absorption (also with respect to conventional syringe-based subcutaneous injection) for longer than 6 months in diabetic mice, and by 11 days in diabetic minipigs (from 2 to 13 days, under standard CSII-wearing conditions of insulin pump therapy and in a continuous basal-plus-bolus-infusion setting). The implanted gel displayed anti-inflammatory and anti-foreign-body-reaction properties and promoted the local formation of new blood vessels. The gel is subcutaneously injected before the tip of catheter is inserted into it, and should be generally applicable to CSII catheters and other implantable devices.

Towards single cell encapsulation for precision biology and medicine

The primary impetus of therapeutic cell encapsulation in the past several decades has been to broaden the options for donor cell sources by countering against immune-mediated rejection. However, another significant advantage of encapsulation is to provide donor cells with physiologically relevant cues that become compromised in disease. The advances in biomaterial design have led to the fundamental insight that cells sense and respond to various signals encoded in materials, ranging from biochemical to mechanical cues. The biomaterial design for cell encapsulation is becoming more sophisticated in controlling specific aspects of cellular phenotypes and more precise down to the single cell level. This recent progress offers a paradigm shift by designing single cell-encapsulating materials with predefined cues to precisely control donor cells after transplantation.

Emerging strategies to bypass transplant rejection via biomaterial-assisted immunoengineering: Insights from islets and beyond

Novel transplantation techniques are currently under development to preserve the function of impaired tissues or organs. While current technologies can enhance the survival of recipients, they have remained elusive to date due to graft rejection by undesired in vivo immune responses despite systemic prescription of immunosuppressants. The need for life-long immunomodulation and serious adverse effects of current medicines, the development of novel biomaterial-based immunoengineering strategies has attracted much attention lately. Immunomodulatory 3D platforms can alter immune responses locally and/or prevent transplant rejection through the protection of the graft from the attack of immune system. These new approaches aim to overcome the complexity of the long-term administration of systemic immunosuppressants, including the risks of infection, cancer incidence, and systemic toxicity. In addition, they can decrease the effective dose of the delivered drugs via direct delivery at the transplantation site. In this review, we comprehensively address the immune rejection mechanisms, followed by recent developments in biomaterial-based immunoengineering strategies to prolong transplant survival. We also compare the efficacy and safety of these new platforms with conventional agents. Finally, challenges and barriers for the clinical translation of the biomaterial-based immunoengineering transplants and prospects are discussed.

Microfluidic Generation of Thin-Shelled Polyethylene Glycol-Tyramine Microgels for Non-Invasive Delivery of Immunoprotected β-Cells

Transplantation of microencapsulated pancreatic cells is emerging as a promising therapy to replenish β-cell mass lost from auto-immune nature of type I diabetes mellitus (T1DM). This strategy intends to use micrometer-sized microgels to provide immunoprotection to transplanted cells to avoid chronic application of immunosuppression. Clinical application of encapsulation has remained elusive due to often limited production throughputs and body's immunological reactions to implanted materials. This article presents a high-throughput fabrication of monodisperse, non-immunogenic, non-degradable, immunoprotective, semi-permeable, enzymatically-crosslinkable polyethylene glycol-tyramine (PEG-TA) microgels for β-cell microencapsulation. Monodisperse β-cell laden microgels of ≈120 µm, with a shell thickness of 20 µm are produced using an outside-in crosslinking strategy. Microencapsulated β-cells rapidly self-assemble into islet-sized spheroids. Immunoprotection of the microencapsulated is demonstrated by inability of FITC-IgG antibodies to diffuse into cell-laden microgels and NK-cell inability to kill microencapsulated β-cells. Multiplexed ELISA analysis on live blood immune reactivity confirms limited immunogenicity. Microencapsulated MIN6β1 spheroids remain glucose responsive for 28 days in vitro, and able to restore normoglycemia 5 days post-implantation in diabetic mice without notable amounts of cell death. In short, PEG-TA microgels effectively protect implanted cells from the host's immune system while being viable and functional, validating this strategy for the treatment of T1DM.

Recent advances in endocrine organoids for therapeutic application

The endocrine system, consisting of the hypothalamus, pituitary, endocrine glands, and hormones, plays a critical role in hormone metabolic interactions. The complexity of the endocrine system is a significant obstacle to understanding and treating endocrine disorders. Notably, advances in endocrine organoid generation allow a deeper understanding of the endocrine system by providing better comprehension of molecular mechanisms of pathogenesis. Here, we highlight recent advances in endocrine organoids for a wide range of therapeutic applications, from cell transplantation therapy to drug toxicity screening, combined with development in stem cell differentiation and gene editing technologies. In particular, we provide insights into the transplantation of endocrine organoids to reverse endocrine dysfunctions and progress in developing strategies for better engraftments. We also discuss the gap between preclinical and clinical research. Finally, we provide future perspectives for research on endocrine organoids for the development of more effective treatments for endocrine disorders.

Enhancing longevity of immunoisolated pancreatic islet grafts by modifying both the intracapsular and extracapsular environment

Type 1 diabetes mellitus (T1DM) is a chronic metabolic disease characterized by autoimmune destruction of pancreatic β cells. Transplantation of immunoisolated pancreatic islets might treat T1DM in the absence of chronic immunosuppression. Important advances have been made in the past decade as capsules can be produced that provoke minimal to no foreign body response after implantation. However, graft survival is still limited as islet dysfunction may occur due to chronic damage to islets during islet isolation, immune responses induced by inflammatory cells, and nutritional issues for encapsulated cells. This review summarizes the current challenges for promoting longevity of grafts. Possible strategies for improving islet graft longevity are also discussed, including supplementation of the intracapsular milieu with essential survival factors, promotion of vascularization and oxygenation near capsules, modulation of biomaterials, and co-transplantation of accessory cells. Current insight is that both the intracapsular as well as the extracapsular properties should be improved to achieve long-term survival of islet-tissue. Some of these approaches reproducibly induce normoglycemia for more than a year in rodents. Further development of the technology requires collective research efforts in material science, immunology, and endocrinology. STATEMENT OF SIGNIFICANCE: Islet immunoisolation allows for transplantation of insulin producing cells in absence of immunosuppression and might facilitate the use of xenogeneic cell sources or grafting of cells obtained from replenishable cell sources. However, a major challenge to date is to create a microenvironment that supports long-term graft survival. This review provides a comprehensive overview of the currently identified factors that have been demonstrated to be involved in either stimulating or reducing islet graft survival in immunoisolating devices and discussed current strategies to enhance the longevity of encapsulated islet grafts as treatment for type 1 diabetes. Although significant challenges remain, interdisciplinary collaboration across fields may overcome obstacles and facilitate the translation of encapsulated cell therapy from the laboratory to clinical application.

Algal Phycocolloids: Bioactivities and Pharmaceutical Applications

Seaweeds are abundant sources of diverse bioactive compounds with various properties and mechanisms of action. These compounds offer protective effects, high nutritional value, and numerous health benefits. Seaweeds are versatile natural sources of metabolites applicable in the production of healthy food, pharmaceuticals, cosmetics, and fertilizers. Their biological compounds make them promising sources for biotechnological applications. In nature, hydrocolloids are substances which form a gel in the presence of water. They are employed as gelling agents in food, coatings and dressings in pharmaceuticals, stabilizers in biotechnology, and ingredients in cosmetics. Seaweed hydrocolloids are identified in carrageenan, alginate, and agar. Carrageenan has gained significant attention in pharmaceutical formulations and exhibits diverse pharmaceutical properties. Incorporating carrageenan and natural polymers such as chitosan, starch, cellulose, chitin, and alginate. It holds promise for creating biodegradable materials with biomedical applications. Alginate, a natural polysaccharide, is highly valued for wound dressings due to its unique characteristics, including low toxicity, biodegradability, hydrogel formation, prevention of bacterial infections, and maintenance of a moist environment. Agar is widely used in the biomedical field. This review focuses on analysing the therapeutic applications of carrageenan, alginate, and agar based on research highlighting their potential in developing innovative drug delivery systems using seaweed phycocolloids.

Developments in stem cell-derived islet replacement therapy for treating type 1 diabetes

The generation of islet-like endocrine clusters from human pluripotent stem cells (hPSCs) has the potential to provide an unlimited source of insulin-producing β cells for the treatment of diabetes. In order for this cell therapy to become widely adopted, highly functional and well-characterized stem cell-derived islets (SC-islets) need to be manufactured at scale. Furthermore, successful SC-islet replacement strategies should prevent significant cell loss immediately following transplantation and avoid long-term immune rejection. This review highlights the most recent advances in the generation and characterization of highly functional SC-islets as well as strategies to ensure graft viability and safety after transplantation.

Engineered collagen polymeric materials create noninflammatory regenerative microenvironments that avoid classical foreign body responses

The efficacy and longevity of medical implants and devices is largely determined by the host immune response, which extends along a continuum from pro-inflammatory/pro-fibrotic to anti-inflammatory/pro-regenerative. Using a rat subcutaneous implantation model, along with histological and transcriptomics analyses, we characterized the tissue response to a collagen polymeric scaffold fabricated from polymerizable type I oligomeric collagen (Oligomer) in comparison to commercial synthetic and collagen-based products. In contrast to commercial biomaterials, no evidence of an immune-mediated foreign body reaction, fibrosis, or bioresorption was observed with Oligomer scaffolds for beyond 60 days. Oligomer scaffolds were noninflammatory, eliciting minimal innate inflammation and immune cell accumulation similar to sham surgical controls. Genes associated with Th2 and regulatory T cells were instead upregulated, implying a novel pathway to immune tolerance and regenerative remodeling for biomaterials.

Sulfobetaine-based ultrathin coatings as effective antifouling layers for implantable neuroprosthetic devices

Foreign body response (FBR), inflammation, and fibrotic encapsulation of neural implants remain major problems affecting the impedance of the electrode-tissue interface and altering the device performance. Adhesion of proteins and cells (e.g., pro-inflammatory macrophages, and fibroblasts) triggers the FBR cascade and can be diminished by applying antifouling coatings onto the implanted devices. In this paper, we report the deposition and characterization of a thin (±6 nm) sulfobetaine-based coating onto microfabricated platinum electrodes and cochlear implant (CI) electrode arrays. We found that this coating has stable cell and protein-repellent properties, for at least 31 days in vitro, not affected by electrical stimulation protocols. Additionally, its effect on the electrochemical properties relevant to stimulation (i.e., impedance, charge injection capacity) was negligible. When applied to clinical CI electrode arrays, the film was successful at inhibiting fibroblast adhesion on both the silicone packaging and the platinum/iridium electrodes. In vitro, in fibroblast cultures, coated CI electrode arrays maintained impedance values up to five times lower compared to non-coated devices. Our studies demonstrate that such thin sulfobetaine containing layers are stable and prevent protein and cell adhesion in vitro and are compatible for use on CI electrode arrays. Future in vivo studies should be conducted to investigate its ability to mitigate biofouling, fibrosis, and the resulting impedance changes upon long-term implantation in vivo.

Zwitterion and N-halamine functionalized cotton wound dressing with enhanced antifouling, antibacterial, and hemostatic properties

With emerging needs of wound care management, a multi-functional wound dressing is needed. To prevent infection and reduce patient suffering, antibacterial efficacy against a broad-spectrum of bacteria plus robust antifouling are among the most preferred properties. In this study, a wound dressing was created with antibacterial and anti-fouling capabilities is presented. The approaches used a synthesized tri-functional copolymer comprised of an N-halamine precursor moiety, a marine-inspired surface binding dopamine moiety, and a zwitterionic anti-adhesion moiety bonded onto a commercial cotton gauze. The resulting HaloCare™ wound dressing demonstrated >99.99 % inactivation within 5 min against E. coli and a panel of ESKAPE pathogens plus achieved 98.77 % reduction of non-specific protein binding. HaloCare was also shown to be compatible with hemostatic agents without impacting hemostatic efficacy. HaloCare shows great potential particularly in traumatic injury events as an infection preventing and hemostatic wound management system.

Orthogonally crosslinked alginate conjugate thermogels with potential for cell encapsulation

Hydrogels with more than one mode of crosslinking have gained interest due to improved control over hydrogel properties such as mechanical strength using multiple stimuli. In this work, sodium alginate was covalently conjugated onto thermoresponsive polyurethanes to prepare hybrid polymers (EPC-Alg) that are responsive to both temperature and Ca²⁺, forming orthogonally crosslinked hydrogels which are non-toxic to cells. Notably, the crosslinks are fully reversible, allowing for gel strength to be modulated via selective removal of either stimulus, or complete deconstruction of the hydrogel network by removing both stimuli. Higher alginate fractions increased the hydrophilicity and Ca²⁺ response of the EPC-Alg hydrogel, enabling tunable modulation of the thermal stability, stiffness and gelation temperatures. The EPC-Alg hydrogel could sustain protein release for a month and encapsulate neural spheroids with high cell viability after 7-day culture, demonstrating feasibility towards 3D cell encapsulation in cell-based biomedical applications such as cell encapsulation and cell therapy.

Chemically engineering cells for precision medicine

Cell-based therapy holds great potential to address unmet medical needs and revolutionize the healthcare industry, as demonstrated by several therapeutics such as CAR-T cell therapy and stem cell transplantation that have achieved great success clinically. Nevertheless, natural cells are often restricted by their unsatisfactory in vivo trafficking and lack of therapeutic payloads. Chemical engineering offers a cost-effective, easy-to-implement engineering tool that allows for strengthening the inherent favorable features of cells and confers them new functionalities. Moreover, in accordance with the trend of precision medicine, leveraging chemical engineering tools to tailor cells to accommodate patients individual needs has become important for the development of cell-based treatment modalities. This review presents a comprehensive summary of the currently available chemically engineered tools, introduces their application in advanced diagnosis and precision therapy, and discusses the current challenges and future opportunities.

Novel hydrogel comprising non-ionic copolymer with various concentrations of pharmacologically active bile acids for cellular injectable gel

Deoxycholic acid (DCA) is a bile acid capable of forming micelles and modifying the properties of hydrogels. We incorporated DCA in sodium alginate (SA) and poloxamer 407 matrices creating novel DCA-copolymer hydrogel for therapeutic delivery. Hydrogels were assessed for common rheological properties. Biocompatibility and biological effect were examined on various cell lines. Cell viability was determent in normal and various hypoxic conditions, and full mitochondrial bioenergetic parameters were assessed in cell lines in order to illustrate hydrogel effects on survival, and cell metabolic profile within the hydrogels. Obtained data suggest that a low dose of DCA in permeable, biocompatible hydrogels can be beneficial for cells to combat hypoxic conditions.

A porcine islet-encapsulation device that enables long-term discordant xenotransplantation in immunocompetent diabetic mice

Islet transplantation is an effective treatment for type 1 diabetes (T1D). However, a shortage of donors and the need for immunosuppressants are major issues. The ideal solution is to develop a source of insulin-secreting cells and an immunoprotective method. No bioartificial pancreas (BAP) devices currently meet all of the functions of long-term glycemic control, islet survival, immunoprotection, discordant xenotransplantation feasibility, and biocompatibility. We developed a device in which porcine islets were encapsulated in a highly stable and permeable hydrogel and a biocompatible immunoisolation membrane. Discordant xenotransplantation of the device into diabetic mice improved glycemic control for more than 200 days. Glycemic control was also improved in new diabetic mice "relay-transplanted" with the device after its retrieval. The easily retrieved devices exhibited almost no adhesion or fibrosis and showed sustained insulin secretion even after the two xenotransplantations. This device has the potential to be a useful BAP for T1D.

Zwitterionic Biomaterials

The term "zwitterionic polymers" refers to polymers that bear a pair of oppositely charged groups in their repeating units. When these oppositely charged groups are equally distributed at the molecular level, the molecules exhibit an overall neutral charge with a strong hydration effect via ionic solvation. The strong hydration effect constitutes the foundation of a series of exceptional properties of zwitterionic materials, including resistance to protein adsorption, lubrication at interfaces, promotion of protein stabilities, antifreezing in solutions, etc. As a result, zwitterionic materials have drawn great attention in biomedical and engineering applications in recent years. In this review, we give a comprehensive and panoramic overview of zwitterionic materials, covering the fundamentals of hydration and nonfouling behaviors, different types of zwitterionic surfaces and polymers, and their biomedical applications.

Alginate microfibers as therapeutic delivery scaffolds and tissue mimics

Alginate, a naturally occurring polysaccharide, has been widely used in cell encapsulation, 3D culture, cell therapy, tissue engineering, and regenerative medicine. Alginate's frequent use comes from its biocompatibility and ability to easily form hydrogel in a variety of forms (e.g. microcapsules, microfibers, and porous scaffolds), which can provide immunoprotection for cell therapy and mimic the extracellular matrix for tissue engineering. During the past 15 years, alginate hydrogel microfibers have attracted more and more attention due to its continuous thin tubular structures (diameter or shell thickness ⩽ 200 µm), high-density cell growth, high handleability and retrievability, and scalability. This review article provides a concise overview of alginate and its resultant hydrogel microfibers for the purpose of promoting multidisciplinary, collaborative, and convergent research in the field. It starts with a historical review of alginate as biomaterials and provides basics about alginate structure, properties, and mechanisms of hydrogel formation, followed by current challenges in effective cell delivery and functional tissue engineering. In particular, this work discusses how alginate microfiber technology could provide solutions to unmet needs with a focus on the current state of the art of alginate microfiber technology and its applications in 3D cell culture, cell delivery, and tissue engineering. At last, we discuss future directions in the perspective of alginate-based advanced technology development in biology and medicine.

Polyzwitterionic Coating of Porous Adsorbents for Therapeutic Apheresis

Adsorbents for whole blood apheresis need to be highly blood compatible to minimize the activation of blood cells on the biomaterial surface. Here, we developed blood-compatible matrices by surface modification with polyzwitterionic polysulfobetainic and polycarboxybetainic coatings. Photoreactive zwitterionic terpolymers were synthesized by free-radical polymerization of zwitterionic, photoreactive, and fluorescent monomers. Upon UV irradiation, the terpolymers were photodeposited and mutually crosslinked on the surface of hydrophobic polystyrene-co-divinylbenzene and hydrophilic polyacrylamide-co-polyacrylate (DALI) beads. Fluorescent microscopy revealed coatings with an average thickness of 5 µm, which were limited to the bead surface. Blood compatibility was assessed based on polymer-induced hemolysis, coagulation parameters, and in vitro tests. The maintenance of the adsorption capacity after coating was studied in human whole blood with cytokines for polystyrene beads (remained capacity 25-67%) and with low-density lipoprotein (remained capacity 80%) for polyacrylate beads. Coating enhanced the blood compatibility of hydrophobic, but not of hydrophilic adsorbents. The most prominent effect was observed on coagulation parameters (e.g., PT, aPTT, TT, and protein C) and neutrophil count. Polycarboxybetaine with a charge spacer of five carbons was the most promising polyzwitterion for the coating of adsorbents for whole blood apheresis.

Type 1 diabetes and engineering enhanced islet transplantation

The development of new therapeutic approaches to treat type 1 diabetes mellitus (T1D) relies on the precise understanding and deciphering of insulin-secreting β-cell biology, as well as the mechanisms responsible for their autoimmune destruction. β-cell or islet transplantation is viewed as a potential long-term therapy for the millions of patients with diabetes. To advance the field of insulin-secreting cell transplantation, two main research areas are currently investigated by the scientific community: (1) the identification of the developmental pathways that drive the differentiation of stem cells into insulin-producing cells, providing an inexhaustible source of cells; and (2) transplantation strategies and engineered transplants to provide protection and enhance the functionality of transplanted cells. In this review, we discuss the biology of pancreatic β-cells, pathology of T1D and current state of β-cell differentiation. We give a comprehensive view and discuss the different possibilities to engineer enhanced insulin-secreting cell/islet transplantation from a translational perspective.

The gut microbiota regulates acute foreign body reaction and tissue repair after biomaterial implantation

We hypothesized that the host microbiome may influence foreign body responses following biomaterial implantation. To test this, we implanted a variety of clinically relevant biomaterials into germ-free or antibiotic-treated mice. Surprisingly, these mice displayed less fibrous tissue deposition, reduced host cell recruitment to the implant site, and differential expression of angiogenic and inflammatory markers. These observations were reversed upon fecal microbiome reconstitution, confirming a causal role of the host microbiome. In a clinically relevant disease model, microbiome-depleted mice cleared hyaluronic acid and bone marrow mononuclear cells from ischemic hind limb tissues more slowly, resulting in an improved therapeutic response. Findings were confirmed in pigs which showed reduced fibrotic responses to a variety of implanted materials. Lastly, we profiled changes in the host microbiome following material implantation, implicating several key bacteria phyla.

Engineering the next generation of cell-based therapeutics

Cell-based therapeutics are an emerging modality with the potential to treat many currently intractable diseases through uniquely powerful modes of action. Despite notable recent clinical and commercial successes, cell-based therapies continue to face numerous challenges that limit their widespread translation and commercialization, including identification of the appropriate cell source, generation of a sufficiently viable, potent and safe product that meets patient- and disease-specific needs, and the development of scalable manufacturing processes. These hurdles are being addressed through the use of cutting-edge basic research driven by next-generation engineering approaches, including genome and epigenome editing, synthetic biology and the use of biomaterials.

Co-transplantation of Islets-Laden Microgels and Biodegradable O2-Generating Microspheres for Diabetes Treatment

Pancreatic islets transplantation is an optimal alternative to exogenous insulin injection for long-term effective type 1 diabetes treatment. However, direct islets transplantation without any protection can induce cell necrosis due to severe host immune rejection. Insufficient O₂ supply induced by the lack of capillary network at the early stage of islets transplantation is another critical constraint limiting islets survival and insulin-secretion function. In this paper, we design a novel co-transplantation system composed of islets-laden nanocomposite microgels and O₂-generating microspheres. In particular, nanocomposite microgels confer the encapsulated islets with simultaneous physical protection and chemical anti-inflammation/immunosuppression by covalently anchoring rapamycin-loaded cyclodextrin nanoparticles to microgel network. Meanwhile, O₂-generating microspheres prepared by blending inorganic peroxides in biodegradable polycaprolactone and polylactic acid can generate in situ O₂ gas and thus avoid hypoxia environment around transplanted islets. In vivo therapeutic effect of diabetic mice proves the reversion of the high blood glucose level back to normoglycemia and superior glucose tolerance for at least 90 days post co-transplantation. In brief, the localized drug and oxygen codelivery, as well as physical protection provided by our co-transplantation system, has the potential to overcome to a large extent the inflammatory, hypoxia, and host immune rejection after islets transplantation. This new strategy may have wider application in other cell replacement therapies.