A retrievable implant for the long-term encapsulation and survival of therapeutic xenogeneic cells

An investigation of functionalized chitosan and alginate multilayer conformal nanocoating on mouse beta cell spheroids as a model for pancreatic islet transplantation

Multilayer conformal coatings have been shown to provide a nanoscale barrier between cells and their environment with adequate stability, while regulating the diffusion of nutrition and waste across the cell membrane. The coating method aims to minimize capsule thickness and implant volume while reducing the need for immunosuppressive drugs, making it a promising approach for islet cell encapsulation in clinical islet transplantation for the treatment of Type 1 diabetes. This study introduces an immunoprotective nanocoating obtained through electrostatic interaction between quaternized phosphocholine-chitosan (PC-QCH) and tetrahydropyran triazole phenyl-alginate (TZ-AL) onto mouse β-cell spheroids. First, successful synthesis of the proposed polyelectrolytes was confirmed with physico-chemical characterization. A coating with an average thickness of 540 nm was obtained with self-assembly of 4-bilayers of PC-QCH/TZ-AL onto MIN6 β-cell spheroids. Surface coating of spheroids did not affect cell viability, metabolic activity, or insulin secretion, when compared to non-coated spheroids. The exposure of the polyelectrolytes to THP-1 monocyte-derived macrophages lead to a reduced level of TNF-α secretion and exposure of coated spheroids to RAW264.7 macrophages showed a decreasing trend in the secretion of TNF-α and IL-6. In addition, coated spheroids were able to establish normoglycemia when implanted into diabetic NOD-SCID mice, demonstrating in vivo biocompatibility and cellular function. These results demonstrate the ability of the PC-QCH/TZ-AL conformal coating to mitigate pro-inflammatory response from macrophages, and thus can be a promising candidate towards nanoencapsulation for cell-based therapy, particularly in type 1 diabetes, where the insulin secreting β-cells are subjected to inflammation and immune cell attack.

Transplantation of pancreatic beta-cell spheroids in mice via non-swellable hydrogel microwells composed of poly(HEMA-co-GelMA)

Pancreatic islet transplantation is an effective treatment for type I diabetes mellitus. However, many problems associated with pancreatic islet engraftment remain unresolved. In this study, we developed a hydrogel microwell device for islet implantation, fabricated by crosslinking gelatin-methacryloyl (GelMA) and 2-hydroxyethyl methacrylate (HEMA) in appropriate proportions. The fabricated hydrogel microwell device could be freeze-dried and restored by immersion in the culture medium at any time, allowing long-term storage and transport of the device for ready-to-use applications. In addition, due to its non-swelling properties, the shape of the wells of the device was maintained. Thus, the device allowed pancreatic β cell lines to form spheroids and increase insulin secretion. Intraperitoneal implantation of the β cell line-seeded GelMA/HEMA hydrogel microwell device reduced blood glucose levels in diabetic mice. In addition, they were easy to handle during transplantation and were removed from the transplant site without peritoneal adhesions or infiltration by inflammatory cells. These results suggest that the GelMA/HEMA hydrogel microwell device can go from spheroid and/or organoid fabrication to transplantation in a single step.

Basic immunologic study as a foundation for engineered therapeutic development

Bioengineering and drug delivery technologies play an important role in bridging the gap between basic scientific discovery and clinical application of therapeutics. To identify the optimal treatment, the most critical stage is to diagnose the problem. Often these two may occur simultaneously or in parallel, but in this review, we focus on bottom-up approaches in understanding basic immunologic phenomena to develop targeted therapeutics. This can be observed in several fields; here, we will focus on one of the original immunotherapy targets-cancer-and one of the more recent targets-regenerative medicine. By understanding how our immune system responds in processes such as malignancies, wound healing, and medical device implantation, we can isolate therapeutic targets for pharmacologic and bioengineered interventions.

Matrix design for optimal pancreatic β cells transplantation

New therapeutic approaches to treat type 1 diabetes mellitus relies on pancreatic islet transplantation. Here, developing immuno-isolation strategies is essential to eliminate the need for systemic immunosuppression after pancreatic islet grafts. A solution is the macro-encapsulation of grafts in semipermeable matrixes with a double function: separating islets from host immune cells and facilitating the diffusion of insulin, glucose, and other metabolites. This study aims to synthesize and characterize different types of gelatin-collagen matrixes to prepare a macro-encapsulation device for pancreatic islets that fulfill these functions. While natural polymers exhibit superior biocompatibility compared to synthetic ones, their mechanical properties are challenging to reproduce. To address this issue, we conducted a comparative analysis between photo-crosslinked gelatin matrixes and chemically crosslinked collagen matrixes. We show that the different crosslinkers and polymerization methods influence the survival and glucose-stimulated insulin production of pancreatic β cells (INS1) in vitro, as well as the in vitro and in vivo stability of the matrix and the immuno-isolation in vivo. Among the matrixes, the stiff multilayer GelMA matrixes (8.5 kPa), fabricated by digital light processing, were the best suited for pancreatic β cells macro-encapsulation regarding these parameters. Within the alveoli of this matrix, pancreatic β cells spontaneously formed aggregates.

Engineering an energy-dissipating hybrid tissue in vivo for obesity treatment

Obesity is a global health challenge with limited therapeutic solutions. Here, we demonstrate the engineering of an energy-dissipating hybrid tissue (EDHT) in the body for weight control. EDHT is constructed by implanting a synthetic gel matrix comprising immunomodulatory signals and functional cells into the recipient mouse. The immunomodulatory signals induce the host stromal cells to create an immunosuppressive niche that protects the functional cells, which are overexpressing the uncoupling protein 1 (UCP1), from immune rejection. Consequently, these endogenous and exogenous cells co-develop a hybrid tissue that sustainedly produces UCP1 to accelerate the host's energy expenditure. Systematic experiments in high-fat diet (HFD) and transgenic (ob/ob) mice show that EDHT efficiently reduces body weight and relieves obesity-associated pathological conditions. Importantly, an 18-month observation for safety assessment excludes cell leakage from EDHT and reports no adverse physiological responses. Overall, EDHT demonstrates convincing efficacy and safety in controlling body weight.

An Autoclavable and Transparent Thermal Cutter for Reliably Sealing Wet Nanofibrous Membranes

Sealing wet porous membranes is a major challenge when fabricating cell encapsulation devices. Herein, we report the development of an Autoclavable Transparent Thermal Cutter (ATTC) for reliably sealing wet nanofibrous membranes. Notably, the ATTC is autoclavable and transparent, thus enabling in situ visualization of the sealing process in a sterile environment and ensuring an appropriate seal. In addition, the ATTC could generate smooth, arbitrary-shaped sealing ends with excellent mechanical properties when sealing PA6, PVDF, and TPU nanofibrous tubes and PP microporous membranes. Importantly, the ATTC could reliably seal wet nanofibrous tubes, which can shoulder a burst pressure up to 313.2 ± 19.3 kPa without bursting at the sealing ends. Furthermore, the ATTC sealing process is highly compatible with the fabrication of cell encapsulation devices, as verified by viability, proliferation, cell escape, and cell function tests. We believe that the ATTC could be used to reliably seal cell encapsulation devices with minimal side effects.

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.

An intrinsically semi-permeable PDMS nanosheet encapsulating adipose tissue-derived stem cells for enhanced angiogenesis

Cell encapsulation devices are expected to be promising tools that can control the release of therapeutic proteins secreted from transplanted cells. The protein permeability of the device membrane is important because it allows the isolation of transplanted cells while enabling the effectiveness of the device. In this study, we investigated free-standing polymeric ultra-thin films (nanosheets) as an intrinsically semi-permeable membrane made from polydimethylsiloxane (PDMS). The PDMS nanosheet with a thickness of 600 nm showed intrinsic protein permeability, and the device fabricated with the PDMS nanosheet showed that VEGF secreted from implanted adipose tissue-derived stem cells (ASCs) could be released for at least 5 days. The ASC encapsulation device promoted angiogenesis and the development of granulation tissue 1 week after transplantation to the subcutaneous area of a mouse. This cell encapsulation device consisting of PDMS nanosheets provides a new method for pre-vascularization of the subcutaneous area in cell transplantation therapy.

Immuno-protective vesicle-crosslinked hydrogel for allogenic transplantation

The longevity of grafts remains a major challenge in allogeneic transplantation due to immune rejection. Systemic immunosuppression can impair graft function and can also cause severe adverse effects. Here, we report a local immuno-protective strategy to enhance post-transplant persistence of allografts using a mesenchymal stem cell membrane-derived vesicle (MMV)-crosslinked hydrogel (MMV-Gel). MMVs are engineered to upregulate expression of Fas ligand (FasL) and programmed death ligand 1 (PD-L1). The MMVs are retained within the hydrogel by crosslinking. The immuno-protective microenvironment of the hydrogel protects allografts by presenting FasL and PD-L1. The binding of these ligands to T effector cells, the dominant contributors to graft destruction and rejection, results in apoptosis of T effector cells and generation of regulatory T cells. We demonstrate that implantation with MMV-Gel prolongs the survival and function of grafts in mouse models of allogeneic pancreatic islet cells and skin transplantation.

Superimposed Electric Field Enhanced Electrospray for High-Throughput and Consistent Cell Encapsulation

Cell encapsulation technology, crucial for advanced biomedical applications, faces challenges in existing microfluidic and electrospray methods. Microfluidic techniques, while precise, can damage vulnerable cells, and conventional electrospray methods often encounter instability and capsule breakage during high-throughput encapsulation. Inspired by the transformation of the working state from unstable dripping to stable jetting triggered by local electric potential, this study introduces a superimposed electric field (SEF)-enhanced electrospray method for cell encapsulation, with improved stability and biocompatibility. Utilizing stiffness theory, the stability of the electrospray, whose stiffness is five times stronger under conical confinement, is quantitatively analyzed. The SEF technique enables rapid, continuous production of ≈300 core-shell capsules per second in an aqueous environment, significantly improving cell encapsulation efficiency. This method demonstrates remarkable potential as exemplified in two key applications: (1) a 92-fold increase in human-derived induced pluripotent stem cells (iPSCs) expansion over 10 d, outperforming traditional 2D cultures in both growth rate and pluripotency maintenance, and (2) the development of liver capsules for steatosis modeling, exhibiting normal function and biomimetic lipid accumulation. The SEF-enhanced electrospray method presents a significant advancement in cell encapsulation technology. It offers a more efficient, stable, and biocompatible approach for clinical transplantation, drug screening, and cell therapy.

Local delivery of stem cell spheroids with protein/polyphenol self-assembling armor to improve myocardial infarction treatment via immunoprotection and immunoregulation

Stem cell therapies have shown great potential for treating myocardial infarction (MI) but are limited by low cell survival and compromised functionality due to the harsh microenvironment at the disease site. Here, we presented a Mesenchymal stem cell (MSC) spheroid-based strategy for MI treatment by introducing a protein/polyphenol self-assembling armor coating on the surface of cell spheroids, which showed significantly enhanced therapeutic efficacy by actively manipulating the hostile pathological MI microenvironment and enabling versatile functionality, including protecting the donor cells from host immune clearance, remodeling the ROS microenvironment and stimulating MSC's pro-healing paracrine secretion. The underlying mechanism was elucidated, wherein the armor protected to prolong MSCs residence at MI site, and triggered paracrine stimulation of MSCs towards immunoregulation and angiogenesis through inducing hypoxia to provoke glycolysis in stem cells. Furthermore, local delivery of coated MSC spheroids in MI rat significantly alleviated local inflammation and subsequent fibrosis via mediation macrophage polarization towards pro-healing M2 phenotype and improved cardiac function. In general, this study provided critical insight into the enhanced therapeutic efficacy of stem cell spheroids coated with a multifunctional armor. It potentially opens up a new avenue for designing immunomodulatory treatment for MI via stem cell therapy empowered by functional biomaterials.

Adhesive anti-fibrotic interfaces on diverse organs

Implanted biomaterials and devices face compromised functionality and efficacy in the long term owing to foreign body reactions and subsequent formation of fibrous capsules at the implant-tissue interfaces1-4. Here we demonstrate that an adhesive implant-tissue interface can mitigate fibrous capsule formation in diverse animal models, including rats, mice, humanized mice and pigs, by reducing the level of infiltration of inflammatory cells into the adhesive implant-tissue interface compared to the non-adhesive implant-tissue interface. Histological analysis shows that the adhesive implant-tissue interface does not form observable fibrous capsules on diverse organs, including the abdominal wall, colon, stomach, lung and heart, over 12 weeks in vivo. In vitro protein adsorption, multiplex Luminex assays, quantitative PCR, immunofluorescence analysis and RNA sequencing are additionally carried out to validate the hypothesis. We further demonstrate long-term bidirectional electrical communication enabled by implantable electrodes with an adhesive interface over 12 weeks in a rat model in vivo. These findings may offer a promising strategy for long-term anti-fibrotic implant-tissue interfaces.

Exploring therapy transport from implantable medical devices using experimentally informed computational methods

Implantable medical devices that can facilitate therapy transport to localized sites are being developed for a number of diverse applications, including the treatment of diseases such as diabetes and cancer, and tissue regeneration after myocardial infraction. These implants can take the form of an encapsulation device which encases therapy in the form of drugs, proteins, cells, and bioactive agents, in semi-permeable membranes. Such implants have shown some success but the nature of these devices pose a barrier to the diffusion of vital factors, which is further exacerbated upon implantation due to the foreign body response (FBR). The FBR results in the formation of a dense hypo-permeable fibrous capsule around devices and is a leading cause of failure in many implantable technologies. One potential method for overcoming this diffusion barrier and enhancing therapy transport from the device is to incorporate local fluid flow. In this work, we used experimentally informed inputs to characterize the change in the fibrous capsule over time and quantified how this impacts therapy release from a device using computational methods. Insulin was used as a representative therapy as encapsulation devices for Type 1 diabetes are among the most-well characterised. We then explored how local fluid flow may be used to counteract these diffusion barriers, as well as how a more practical pulsatile flow regimen could be implemented to achieve similar results to continuous fluid flow. The generated model is a versatile tool toward informing future device design through its ability to capture the expected decrease in insulin release over time resulting from the FBR and investigate potential methods to overcome these effects.

[Closed-loop synthetic gene circuits for cell-based therapies]

Recent advances in synthetic biology have paved the way for new cellular therapies, using cells capable of autonomously treating chronic diseases. These cells integrate a set of genes functioning in a closed-loop synthetic circuit, delivering a therapeutic effector in response to a specific pathological signal. While promising in mice, these therapies face clinical challenges related to safety and feasibility of in vivo implementation. The latest generations of synthetic circuits aim to address these issues through advanced bioengineering strategies outlined in this article.

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.

Covalently grafted human serum albumin coating mitigates the foreign body response against silicone implants in mice

Implantable biomaterials and biosensors are integral components of modern medical systems but often encounter hindrances due to the foreign body response (FBR). Herein, we report an albumin coating strategy aimed at addressing this challenge. Using a facile and scalable silane coupling strategy, human serum albumin (HSA) is covalently grafted to the surface of polydimethylsiloxane (PDMS) implants. This covalently grafted albumin coating remains stable and resistant to displacement by other proteins. Notably, the PDMS with covalently grafted HSA strongly resists the fibrotic capsule formation following a 180-day subcutaneous implantation in C57BL/6 mice. Furthermore, the albumin coating led to reduced recruitment of macrophages and triggered a mild immune activation pattern. Exploration of albumin coatings sourced from various mammalian species has shown that only HSA exhibited a promising anti-FBR effect. The albumin coating method reported here holds the potential to improve and extend the function of silicone-based implants by mitigating the host responses to subcutaneously implanted biomaterials.

An Ultrasoft and Flexible PDMS-Based Balloon-Type Implantable Device for Controlled Drug Delivery

Non-biodegradable implants have undergone extensive investigation as drug delivery devices to enable advanced healthcare toward personalized medicine. However, fibroblast encapsulation is one of the major challenges in all non-biodegradable implants, besides other challenges such as high initial burst, risk of membrane rupture, high onset time, non-conformal contact with tissues, and tissue damage. To tackle such challenges, we propose a novel ultrasoft and flexible balloon-type drug delivery device for unidirectional and long-term controlled release. The ultrasoft balloon-type device (USBD) was fabricated by using selective bonding between 2 polydimethylsiloxane (PDMS) membranes and injecting a fluid into the non-bonded area between them. The balloon acted as a reservoir containing a liquid drug, and at the same time, the membrane of the balloon itself acted as the pathway for release based on diffusion. The release was modulated by tuning the thickness and composition of the PDMS membrane. Regardless of the thickness and composition, all devices exhibited zero-order release behavior. The longest zero-order release and nearly zero-order release were achieved for 30 days and 58 days at a release rate of 1.16 μg/day and 1.68 μg/day, respectively. In vivo evaluation was performed for 35 days in living rats, where the USBD maintained zero-order and nearly zero-order release for 28 days and 35 days, respectively. Thanks to the employment of ultrasoft and flexible membranes and device design, the USBD could achieve minimal tissue damage and foreign body responses. It is expected that the proposed device may provide a novel approach for long-term drug delivery with new therapeutic modalities.

Microplastic label in microencapsulation field - Consequence of shell material selection

Plastics make our lives easier in many ways; however, if they are not appropriately disposed of or recycled, they may end up in the environment where they stay for centuries and degrade into smaller and smaller pieces, called microplastics. Each year, approximately 42000 tonnes of microplastics end up in the environment when products containing them are used. According to the European Chemicals Agency (ECHA) one of the significant sources of microplastics are microcapsules formulated in home care and consumer care products. As part of the EU's plastics strategy, ECHA has proposed new regulations to ban intentionally added microplastics starting from 2022. It means that the current cross-linked microcapsules widely applied in consumer goods must be transformed into biodegradable shell capsules. The aim of this review is to provide the readers with a comprehensive and in-depth understanding of recent developments in the art of microencapsulation. Thus, considering the chemical structure of the capsule shell's materials, we discuss whether microcapsules should also be categorized as microplastic and therefore, feared and avoided or whether they should be used despite the persisting concern.

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.

A bioengineered artificial interstitium supports long-term islet xenograft survival in nonhuman primates without immunosuppression

Cell-based therapies hold promise for many chronic conditions; however, the continued need for immunosuppression along with challenges in replacing cells to improve durability or retrieving cells for safety are major obstacles. We subcutaneously implanted a device engineered to exploit the innate transcapillary hydrostatic and colloid osmotic pressure generating ultrafiltrate to mimic interstitium. Long-term stable accumulation of ultrafiltrate was achieved in both rodents and nonhuman primates (NHPs) that was chemically similar to serum and achieved capillary blood oxygen concentration. The majority of adult pig islet grafts transplanted in non-immunosuppressed NHPs resulted in xenograft survival >100 days. Stable cytokine levels, normal neutrophil to lymphocyte ratio, and a lack of immune cell infiltration demonstrated successful immunoprotection and averted typical systemic changes related to xenograft transplant, especially inflammation. This approach eliminates the need for immunosuppression and permits percutaneous access for loading, reloading, biopsy, and recovery to de-risk the use of "unlimited" xenogeneic cell sources to realize widespread clinical translation of cell-based therapies.

Review of electrospun microtube array membrane (MTAM)-a novel new class of hollow fiber for encapsulated cell therapy (ECT) in clinical applications

Encapsulated cell therapy (ECT) shows significant potential for treating neurodegenerative disorders including Alzheimer's and Parkinson's, which currently lack curative medicines and must be managed symptomatically. This novel technique encapsulates functional cells with a semi-permeable membrane, providing protection while enabling critical nutrients and therapeutic substances to pass through. Traditional ECT procedures, on the other hand, pose difficulties in terms of cell survival and retrieval. We introduce the Microtube Array Membrane (MTAM), a revolutionary technology that solves these constraints, in this comprehensive overview. Microtube Array Membrane has distinct microstructures that improve encapsulated cells' long-term viability by combining the advantages of macro and micron scales. Importantly, the MTAM platform improves biosafety by allowing the entire encapsulated unit to be retrieved in the event of an adverse reaction. Our findings show that MTAM-based ECT has a great potential in a variety of illness situations. For cancer treatment, hybridoma cells secreting anti-CEACAM 6 antibodies inhibit triple-negative breast cancer cell lines for an extended period of time. In animal brain models of Alzheimer's disease, hybridoma cells secreting anti-pTau antibodies successfully reduce pTau buildup, accompanied by improvements in memory performance. In mouse models, MTAM-encapsulated primary cardiac mesenchymal stem cells dramatically improve overall survival and heart function. These findings illustrate the efficacy and adaptability of MTAM-based ECT in addressing major issues such as immunological isolation, cell viability, and patient safety. We provide new possibilities for the treatment of neurodegenerative illnesses and other conditions by combining the potential of ECT with MTAM. Continued research and development in this subject has a lot of promise for developing cell therapy and giving hope to people suffering from chronic diseases.

Magnetically-actuated microcages for cells entrapment, fabricated by laser direct writing via two photon polymerization

The manipulation of biological materials at cellular level constitutes a sine qua non and provocative research area regarding the development of micro/nano-medicine. In this study, we report on 3D superparamagnetic microcage-like structures that, in conjunction with an externally applied static magnetic field, were highly efficient in entrapping cells. The microcage-like structures were fabricated using Laser Direct Writing via Two-Photon Polymerization (LDW via TPP) of IP-L780 biocompatible photopolymer/iron oxide superparamagnetic nanoparticles (MNPs) composite. The unique properties of LDW via TPP technique enabled the reproduction of the complex architecture of the 3D structures, with a very high accuracy i.e., about 90 nm lateral resolution. 3D hyperspectral microscopy was employed to investigate the structural and compositional characteristics of the microcage-like structures. Scanning Electron Microscopy coupled with Energy Dispersive X-Ray Spectroscopy was used to prove the unique features regarding the morphology and the functionality of the 3D structures seeded with MG-63 osteoblast-like cells. Comparative studies were made on microcage-like structures made of IP-L780 photopolymer alone (i.e., without superparamagnetic properties). We found that the cell-seeded structures made by IP-L780/MNPs composite actuated by static magnetic fields of 1.3 T were 13.66 ± 5.11 folds (p < 0.01) more efficient in terms of cells entrapment than the structures made by IP-L780 photopolymer alone (i.e., that could not be actuated magnetically). The unique 3D architecture of the microcage-like superparamagnetic structures and their actuation by external static magnetic fields acted in synergy for entrapping osteoblast-like cells, showing a significant potential for bone tissue engineering applications.

Controlled swelling of biomaterial devices for improved antifouling polymer coatings

Nonspecific interactions between cells and implantable elastomers often leads to failure modes for devices such as catheters, cosmetic and reconstructive implants, and sensors. To reduce these interactions, device surfaces can be coated with hydrophilic polymers, where greater polymer density enhances antifouling properties. Although graft-from coating techniques result in higher density polymer films and lower fouling in controlled settings, simpler graft-to methods show similar results on complex implanted devices, despite limited density. To address the need for improved graft-to methods, we developed Graft then shrink (GtS) where elastomeric materials are temporarily swollen during polymer grafting. Herein, we demonstrate a graft-to based method for poly(oligo(ethylene glycol) methyl ether methacrylate) (pOEGMA) on swollen silicone, GtS, that enhances grafted polymer content and fouling resistance. Total grafted polymer content of pOEGMA on toluene swollen silicone increased over ~ 13 × compared to non-swollen controls, dependent on the degree of silicone swelling. Increases in total grafted polymer within the top 200 µm of the material led to bacterial and mammalian cell adhesion reductions of 75% and 91% respectively, compared to Shrink then Graft (StG) antifouling polymer coated controls. GtS allows for the simple 3D coating of swellable elastomers (e.g., silicone medical devices) with improved antifouling pOEGMA coatings.

Electrocatalytic on-site oxygenation for transplanted cell-based-therapies

Implantable cell therapies and tissue transplants require sufficient oxygen supply to function and are limited by a delay or lack of vascularization from the transplant host. Previous exogenous oxygenation strategies have been bulky and had limited oxygen production or regulation. Here, we show an electrocatalytic approach that enables bioelectronic control of oxygen generation in complex cellular environments to sustain engineered cell viability and therapy under hypoxic stress and at high cell densities. We find that nanostructured sputtered iridium oxide serves as an ideal catalyst for oxygen evolution reaction at neutral pH. We demonstrate that this approach exhibits a lower oxygenation onset and selective oxygen production without evolution of toxic byproducts. We show that this electrocatalytic on site oxygenator can sustain high cell loadings (>60k cells/mm3) in hypoxic conditions in vitro and in vivo. Our results showcase that exogenous oxygen production devices can be readily integrated into bioelectronic platforms, enabling high cell loadings in smaller devices with broad applicability.

A wireless, battery-free device enables oxygen generation and immune protection of therapeutic xenotransplants in vivo

The immune isolation of cells within devices has the potential to enable long-term protein replacement and functional cures for a range of diseases, without requiring immune suppressive therapy. However, a lack of vasculature and the formation of fibrotic capsules around cell immune-isolating devices limits oxygen availability, leading to hypoxia and cell death in vivo. This is particularly problematic for pancreatic islet cells that have high O2 requirements. Here, we combine bioelectronics with encapsulated cell therapies to develop the first wireless, battery-free oxygen-generating immune-isolating device (O2-Macrodevice) for the oxygenation and immune isolation of cells in vivo. The system relies on electrochemical water splitting based on a water-vapor reactant feed, sustained by wireless power harvesting based on a flexible resonant inductive coupling circuit. As such, the device does not require pumping, refilling, or ports for recharging and does not generate potentially toxic side products. Through systematic in vitro studies with primary cell lines and cell lines engineered to secrete protein, we demonstrate device performance in preventing hypoxia in ambient oxygen concentrations as low as 0.5%. Importantly, this device has shown the potential to enable subcutaneous (SC) survival of encapsulated islet cells, in vivo in awake, freely moving, immune-competent animals. Islet transplantation in Type I Diabetes represents an important application space, and 1-mo studies in immune-competent animals with SC implants show that the O2-Macrodevice allows for survival and function of islets at high densities (~1,000 islets/cm2) in vivo without immune suppression and induces normoglycemia in diabetic animals.

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.

Engineering a versatile and retrievable cell macroencapsulation device for the delivery of therapeutic proteins

Encapsulated cell therapy holds a great potential to deliver sustained levels of highly potent therapeutic proteins to patients and improve chronic disease management. A versatile encapsulation device that is biocompatible, scalable, and easy to administer, retrieve, or replace has yet to be validated for clinical applications. Here, we report on a cargo-agnostic, macroencapsulation device with optimized features for protein delivery. It is compatible with adherent and suspension cells, and can be administered and retrieved without burdensome surgical procedures. We characterized its biocompatibility and showed that different cell lines producing different therapeutic proteins can be combined in the device. We demonstrated the ability of cytokine-secreting cells encapsulated in our device and implanted in human skin to mobilize and activate antigen-presenting cells, which could potentially serve as an effective adjuvant strategy in cancer immunization therapies. We believe that our device may contribute to cell therapies for cancer, metabolic disorders, and protein-deficient diseases.

Screening hydrogels for antifibrotic properties by implanting cellularly barcoded alginates in mice and a non-human primate

Screening implantable biomaterials for antifibrotic properties is constrained by the need for in vivo testing. Here we show that the throughput of in vivo screening can be increased by cellularly barcoding a chemically modified combinatorial library of hydrogel formulations. The method involves the implantation of a mixture of alginate formulations, each barcoded with human umbilical vein endothelial cells from different donors, and the association of the identity and performance of each formulation by genotyping single nucleotide polymorphisms of the cells via next-generation sequencing. We used the method to screen 20 alginate formulations in a single mouse and 100 alginate formulations in a single non-human primate, and identified three lead hydrogel formulations with antifibrotic properties. Encapsulating human islets with one of the formulations led to long-term glycaemic control in a mouse model of diabetes, and coating medical-grade catheters with the other two formulations prevented fibrotic overgrowth. High-throughput screening of barcoded biomaterials in vivo may help identify formulations that enhance the long-term performance of medical devices and of biomaterial-encapsulated therapeutic cells.

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.

A versatile genomic transgenesis platform with enhanced λ integrase for human Expi293F cells

Reliable cell-based platforms to test and/or produce biologics in a sustainable manner are important for the biotech industry. Utilizing enhanced λ integrase, a sequence-specific DNA recombinase, we developed a novel transgenesis platform involving a fully characterized single genomic locus as an artificial landing pad for transgene insertion in human Expi293F cells. Importantly, transgene instability and variation in expression were not observed in the absence of selection pressure, thus enabling reliable long-term biotherapeutics testing or production. The artificial landing pad for λ integrase can be targeted with multi-transgene constructs and offers future modularity involving additional genome manipulation tools to generate sequential or nearly seamless insertions. We demonstrated broad utility with expression constructs for anti PD-1 monoclonal antibodies and showed that the orientation of heavy and light chain transcription units profoundly affected antibody expression levels. In addition, we demonstrated encapsulation of our PD-1 platform cells into bio-compatible mini-bioreactors and the continued secretion of antibodies, thus providing a basis for future cell-based applications for more effective and affordable therapies.

Controlled Interfacial Polymer Self-Assembly Coordinates Ultrahigh Drug Loading and Zero-Order Release in Particles Prepared under Continuous Flow

Microparticles are successfully engineered through controlled interfacial self-assembly of polymers to harmonize ultrahigh drug loading with zero-order release of protein payloads. To address their poor miscibility with carrier materials, protein molecules are transformed into nanoparticles, whose surfaces are covered with polymer molecules. This polymer layer hinders the transfer of cargo nanoparticles from oil to water, achieving superior encapsulation efficiency (up to 99.9%). To control payload release, the polymer density at the oil-water interface is enhanced, forming a compact shell for microparticles. The resultant microparticles can harvest up to 49.9% mass fraction of proteins with zero-order release kinetics in vivo, enabling an efficient glycemic control in type 1 diabetes. Moreover, the precise control of engineering process offered through continuous flow results in high batch-to-batch reproducibility and, ultimately, excellent scale-up feasibility.

A new paradigm in transplant immunology: At the crossroad of synthetic biology and biomaterials

Solid organ transplant (SOT) recipients require meticulously tailored immunosuppressive regimens to minimize graft loss and mortality. Traditional approaches focus on inhibiting effector T cells, while the intricate and dynamic immune responses mediated by other components remain unsolved. Emerging advances in synthetic biology and material science have provided novel treatment modalities with increased diversity and precision to the transplantation community. This review investigates the active interface between these two fields, highlights how living and non-living structures can be engineered and integrated for immunomodulation, and discusses their potential application in addressing the challenges in SOT clinical practice.

Engineered combinatorial cell device for wound healing and bone regeneration

Growth factors are the key regulators that promote tissue regeneration and healing processes. While the effects of individual growth factors are well documented, a combination of multiple secreted growth factors underlies stem cell-mediated regeneration. To avoid the potential dangers and labor-intensive individual approach of stem cell therapy while maintaining their regeneration-promoting effects based on multiple secreted growth factors, we engineered a "mix-and-match" combinatorial platform based on a library of cell lines producing growth factors. Treatment with a combination of growth factors secreted by engineered mammalian cells was more efficient than with individual growth factors or even stem cell-conditioned medium in a gap closure assay. Furthermore, we implemented in a mouse model a device for allogenic cell therapy for an in situ production of growth factors, where it improved cutaneous wound healing. Augmented bone regeneration was achieved on calvarial bone defects in rats treated with a cell device secreting IGF, FGF, PDGF, TGF-β, and VEGF. In both in vivo models, the systemic concentration of secreted factors was negligible, demonstrating the local effect of the regeneration device. Finally, we introduced a genetic switch that enables temporal control over combinations of trophic factors released at different stages of regeneration mimicking the maturation of natural wound healing to improve therapy and prevent scar formation.

Lipid Deposition Profiles Influence Foreign Body Responses

Fibrosis remains a significant cause of failure in implanted biomedical devices and early absorption of proteins on implant surfaces has been shown to be a key instigating factor. However, lipids can also regulate immune activity and their presence may also contribute to biomaterial-induced foreign body responses (FBR) and fibrosis. Here it is demonstrated that the surface presentation of lipids on implant affects FBR by influencing reactions of immune cells to materials as well as their resultant inflammatory/suppressive polarization. Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) is employed to characterize lipid deposition on implants that are surface-modified chemically with immunomodulatory small molecules. Multiple immunosuppressive phospholipids (phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine, and sphingomyelin) are all found to deposit preferentially on implants with anti-FBR surface modifications in mice. Significantly, a set of 11 fatty acids is enriched on unmodified implanted devices that failed in both mice and humans, highlighting relevance across species. Phospholipid deposition is also found to upregulate the transcription of anti-inflammatory genes in murine macrophages, while fatty acid deposition stimulated the expression of pro-inflammatory genes. These results provide further insights into how to improve the design of biomaterials and medical devices to mitigate biomaterial material-induced FBR and fibrosis.

An electrospun macrodevice for durable encapsulation of human cells with consistent secretion of therapeutic antibodies

Frequent subcutaneous or intravenous administrations of therapeutic biomolecules can be costly and inconvenient for patients. Implantation of encapsulated recombinant cells represents a promising approach for the sustained delivery of biotherapeutics. However, foreign body and fibrotic response against encapsulation materials results in drastically reduced viability of encapsulated cells, presenting a major engineering challenge for biocompatibility. Here, we show that the multi-laminate electrospun retrievable macrodevice (Bio-Spun) protects genetically modified human cells after subcutaneous implant in mice. We describe here a biocompatible nanofiber device that limits fibrosis and extends implant survival. For more than 150 days, these devices supported human cells engineered to secrete the antibodies: vedolizumab, ustekinumab, and adalimumab, while eliciting minimal fibrotic response in mice. The porous electrospun cell chamber allowed secretion of the recombinant antibodies into the host bloodstream, and prevented infiltration of host cells into the chamber. High plasma levels (>50 μg/mL) of antibody were maintained in the optimized devices for more than 5 months. Our findings demonstrate that macrodevices constructed from electrospun materials are effective in protecting genetically engineered cells for the sustained administration of recombinant therapeutic antibodies.

Hydrogel-Bondable Asymmetric Planar Membranes with Hierarchical Pore Structures for Cell Scaffolding and Encapsulation

Biomaterials for cell replacement therapy could facilitate the delivery, function, and retrieval of transplanted therapeutic cells. However, the limited capacity to accommodate a sufficient quantity of cells in biomedical devices has hindered the success of clinical application, resulting from the suboptimal spatial organization of cells and insufficient permeation of nutrients in the materials. Herein, through the immersion-precipitation phase transfer (IPPT) process from polyether sulfone (PES), we develop planar asymmetric membranes with a hierarchical pore architecture spanning from nanopores (∼20 nm) in the dense skin and open-ended microchannel arrays with gradient pore size increasing vertically from microns to ∼100 μm. The nanoporous skin would be an ultrathin diffusion barrier, while the microchannels could support high-density cell loading by acting as separate chambers allowing uniform distribution of cells in the scaffold. Alginate hydrogel could permeate into the channels and form a sealing layer after gelation, which could slow down the invasion of host immune cells into the scaffold. The hybrid thin-sheet encapsulation system (∼400 μm thick) could protect allogeneic cells over half-year after intraperitoneal (IP) implantation in immune-competent mice. Such structural membranes and plastic-hydrogel hybrids of thin dimensions could find important applications in cell delivery therapy.

Oral formulation of Wnt inhibitor complex reduces inflammation and fibrosis in intraperitoneal implants in vivo

The use of implantable biomaterials to replace physiological and anatomical functions has been widely investigated in the clinic. However, the selection of biomaterials is crucial for long-term function, and the implantation of certain biomaterials can cause inflammatory and fibrotic processes, triggering a foreign body reaction that leads to loss of function and consequent need for removal. Specifically, the Wnt signaling pathway controls the healing process of the human body, and its dysregulation can result in inflammation and fibrosis, such as in peritoneal fibrosis. Here, we assessed the effects of daily oral administration of a Wnt pathway inhibitor complex (CD:LGK974) to reduce the inflammatory, fibrotic, and angiogenic processes caused by intraperitoneal implants. CD:LGK974 significantly reduced the infiltration of immune cells and release of inflammatory cytokines in the implant region compared to the control groups. Furthermore, CD:LGK974 inhibited collagen deposition and reduced the expression of pro-fibrotic α-SMA and TGF-β1, confirming fibrosis reduction. Finally, the CD:LGK974 complex decreased VEGF levels and both the number and area of blood vessels formed, suggesting decreased angiogenesis. This work introduces a potential new application of the Wnt inhibitor complex to reduce peritoneal fibrosis and the rejection of implants at the intraperitoneal site, possibly allowing for longer-term functionality of existing clinical biomaterials.

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.

Degradable Biocompatible Porous Microtube Scaffold for Extended Donor Cell Survival and Activity

Cell therapy has significant therapeutic potential but is often limited by poor donor cell retention and viability at the host implantation site. Biomaterials can improve cell retention by providing cells with increased cell-cell and cell-matrix contacts and materials that allow three-dimensional cell culture to better recapitulate native cell morphology and function. In this study, we engineered a scaffold that allows for cell encapsulation and sustained three-dimensional cell culture. Since cell therapy is largely driven by paracrine secretions, the material was fabricated by electrospinning to have a large internal surface area, micrometer-thin walls, and nanoscale surface pores to allow for nutrient exchange without early cell permeation. The material is degradable, which allows for less invasive removal of the implant. Here, a biodegradable poly(lactic-co-glycolic acid) (PLGA) microtube array membrane was fabricated. In vitro testing showed that the material supported the culture of human dermal fibroblasts for at least 21 days, with paracrine secretion of pro-angiogenic FGF2. In vivo xenotransplantation of human cells in an immunocompetent mouse showed that donor cells could be maintained for more than one month and the material showed no obvious toxicity. Analysis of gene expression and tissue histology surrounding the implant showed that the material produced muted inflammatory and immune responses compared to a permanent implant and increased markers of angiogenesis.

Partially Oxidized Alginate as a Biodegradable Carrier for Glucose-Responsive Insulin Delivery and Islet Cell Replacement Therapy

Self-regulated insulin delivery that mimics native pancreas function has been a long-term goal for diabetes therapies. Two approaches towards this goal are glucose-responsive insulin delivery and islet cell transplantation therapy. Here, biodegradable, partially oxidized alginate carriers for glucose-responsive nanoparticles or islet cells are developed. Material composition and formulation are tuned in each of these contexts to enable glycemic control in diabetic mice. For injectable, glucose-responsive insulin delivery, 0.5 mm 2.5% oxidized alginate microgels facilitate repeat dosing and consistently provide 10 days of glycemic control. For islet cell transplantation, 1.5 mm capsules comprised of a blend of unoxidized and 2.5% oxidized alginate maintain cell viability and glycemic control over a period of more than 2 months while reducing the volume of nondegradable material implanted. These data show the potential of these biodegradable carriers for controlled drug and cell delivery for the treatment of diabetes with limited material accumulation in the event of multiple doses.

Porous scaffold for mesenchymal cell encapsulation and exosome-based therapy of ischemic diseases

Ischemic diseases including myocardial infarction (MI) and limb ischemia are some of the greatest causes of morbidity and mortality worldwide. Cell therapy is a potential treatment but is usually limited by poor survival and retention of donor cells injected at the target site. Since much of the therapeutic effects occur via cell-secreted paracrine factors, including extracellular vesicles (EVs), we developed a porous material for cell encapsulation which would improve donor cell retention and survival, while allowing EV secretion. Human donor cardiac mesenchymal cells were used as a model therapeutic cell and the encapsulation system could sustain three-dimensional cell growth and secretion of therapeutic factors. Secretion of EVs and protective growth factors were increased by encapsulation, and secreted EVs had hypoxia-protective, pro-angiogenic activities in in vitro assays. In a mouse model of limb ischemia the implant improved angiogenesis and blood flow, and in an MI model the system preserved ejection fraction %. In both instances, the encapsulation system greatly extended donor cell retention and survival compared to directly injected cells. This system represents a promising therapy for ischemic diseases and could be adapted for treatment of other diseases in the future.

Emerging technologies for genetic control systems in cellular therapies

Progress in synthetic biology has enabled the construction of designer cells that sense biological inputs, and, in response, activate user-defined biomolecular programs. Such engineered cells provide unique opportunities for treating a wide variety of diseases. Current strategies mostly rely on cell-surface receptor systems engineered to convert binding interactions into activation of a transcriptional program. Genetic control systems are emerging as an appealing alternative to receptor-based sensors as they overcome the need for receptor engineering and result in cellular behaviors that operate over therapeutically relevant timescales. Genetic control systems include synthetic gene networks, RNA-based sensors, and post-translational tools. These technologies present fundamental challenges, including the requirement for precise integration with innate pathways, the need for parts orthogonal to existing circuitries, and the metabolic burden induced by such complex cell engineering endeavors. This review discusses the challenges in the design of genetic control systems for cellular therapies and their translational applications.

Immunological response of polysaccharide nanogel-incorporating PEG hydrogels in an in vivo diabetic model

Cell-based therapies hold significant advantages in comparison with the traditional drug-based or injection-based treatments. However, for long-term functional cellular implants, immune acceptance must be established. To accomplish the acceptance of the implanted cells, various biomaterial systems have been studied. Nanogels have shown great potential for modulation of cellular microenvironments, acting as a physical barrier between the immune system and the implant. However, internalization of nano-scale materials by implanted cells is not desirable and is yet to be overcome. In this study, we incorporated acrylate modified cholesterol-bearing pullulan (CHPOA) nanogels into poly (ethylene glycol) diacrylate (PEGDA) hydrogels through covalent crosslinking, where we used visible light-induced photopolymerization. We characterized morphology and swelling properties of CHPOA incorporated PEG composite hydrogels using FE-SEM and gravimetric analysis. Also, we investigated the biocompatibility properties of composite hydrogels in vivo, where we used both healthy and diabetic mice. We induced diabetes in mice using a low dose streptozotocin (STZ) injections and implanted composite hydrogels in both diabetic and healthy mice through subcutaneous route. Immune cell infiltration of the retrieved tissue was examined through histological analysis, where we observed minimum immune response levels of 0-2 rareness, according to ISO standard of biological evaluation of medical devices. Our observation suggests that the composite hydrogel developed here can be used to introduce nanostructured domains into bulk hydrogels and that this system has potential to be used as immunologically acceptable composite material in cellular therapy without internalization of nanoparticles.

Biomarker-driven feedback control of synthetic biology systems for next-generation personalized medicine

Many current clinical therapies for chronic diseases involve administration of drugs using dosage and bioavailability parameters estimated for a generalized population. This standard approach carries the risk of under dosing, which may result in ineffective treatment, or overdosing, which may cause undesirable side effects. Consequently, maintaining a drug concentration in the therapeutic window often requires frequent monitoring, adversely affecting the patient’s quality of life. In contrast, endogenous biosystems have evolved finely tuned feedback control loops that govern the physiological functions of the body based on multiple input parameters. To provide personalized treatment for chronic diseases, therefore, we require synthetic systems that can similarly generate a calibrated therapeutic response. Such engineered autonomous closed-loop devices should incorporate a sensor that actively tracks and evaluates the disease severity based on one or more biomarkers, as well as components that utilize these molecular inputs to bio compute and deliver the appropriate level of therapeutic output. Here, we review recent advances in applications of the closed-loop design principle in biomedical implants for treating severe and chronic diseases, highlighting translational studies of cellular therapies. We describe the engineering principles and components of closed-loop therapeutic devices, and discuss their potential to become a key pillar of personalized medicine.

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.