Cell Encapsulation Research Articles

Providing biomimetic microenvironment for pulp regeneration via hydrogel-mediated sustained delivery of tissue-specific developmental signals

Regenerative endodontic therapy is a promising approach to restore the vitality of necrotic teeth, however, pulp regeneration in mature permanent teeth remains a substantial challenge due to insufficient developmental signals. The dentin is embryologically and histologically similar to the pulp, which contains a cocktail of pulp-specific structural proteins and growth factors, thus we proposed an optimizing strategy to obtain dentin matrix extracted proteins (DMEP) and engineered a DMEP functionalized double network hydrogel, whose physicochemical property was tunable by adjusting polymer concentrations to synchronize with regenerated tissues. In vitro models showed that the biomimetic hydrogel with sustained release of DMEP provided a beneficial microenvironment for the encapsulation, propagation and migration of human dental pulp stem cells (hDPSCs). The odontogenic and angiogenic differentiation of hDPSCs were enhanced as well. To elicit the mechanism hidden in the microenvironment to guide cell fate, RNA sequencing was performed and 109 differential expression of genes were identified, the majority of which enriched in cell metabolism, cell differentiation and intercellular communications. The involvement of ERK, p38 and JNK MAPK signaling pathways in the process was confirmed. Of note, in vivo models showed that the injectable and in situ photo-crosslinkable hydrogel was user-friendly for root canal systems and was capable of inducing the regeneration of highly organized and vascularized pulp-like tissues in root segments that subcutaneously implanted into nude mice. Taken together, this study reported a facile and efficient way to fabricate a cell delivery hydrogel with pulp-specific developmental cues, which exhibited promising application and translation potential in future regenerative endodontic fields.

Spatial atomic layer deposition of nitrogen-doped alumina thin films for high-performance perovskite solar cell encapsulation

An atmospheric-pressure spatial atomic layer deposition (AP-SALD) system is used to deposit nitrogen-doped alumina (N-AlOx) thin-film-encapsulation layers. The rapid nature of the AP-SALD process facilitates deposition of 60-nm layers directly on perovskite solar cells at 130 °C with no damage to the temperature-sensitive perovskite and organic materials. Varying the bubbling of a NH4OH precursor varied the nitrogen concentration from 0.08 to 0.68 at%. These small concentrations were found to have a significant impact on the structural properties of the films and their moisture barrier performance. The N-AlOx thin films had slightly higher growth rates than undoped AlOx, less unwanted hydroxyl and carbon content, and were smoother and more compact, which was attributed to a higher flux of reactive species from the volatile NH4OH. Optical calcium tests showed that the N-AlOx films had lower water-vapor-transmission rates (∼10-5 g/m2/day) than undoped AlOx films and the transmission was minimized for 0.28% nitrogen. The increased compactness of the N-AlOx films is expected to minimize nanoscale percolation pathways, whereas higher nitrogen-defect concentrations may facilitate water permeation through these pathways. The stability of n-i-p and p-i-n perovskite solar cells under standard ISOS-D-1 and ISOS-D-3 testing conditions was significantly enhanced by the encapsulation layers. An N-AlOx encapsulation layer with 0.28% nitrogen improved the T80 value of a p-i-n formamidinium methylammonium lead iodide solar cell from 144 hrs to 855 hrs (ISOS-D-1) and 52 hrs to 300 hrs (ISOS-D-3).

Six‐Month Outdoor Performance Study of Stable Perovskite Solar Cells Under Real Operating Conditions

Perovskite solar cells (PSCs) have sparked great excitement in the photovoltaics community due to their remarkable efficiency, flexibility, and ability to be synthesized at low cost. However, their instability poses a major roadblock to their widespread adoption. Recognizing this challenge, this work describes the performance of stable PSCs operating under real‐life conditions in the Paris area. Two state‐of‐the‐art 2D/3D (HOOC(CH2)4NH3)2PbI4/CH3NH3PbI3 encapsulated cells are considered—one with maximum power point tracking and hourly current–voltage curve measurements, and another connected to a fixed resistive load. Their performance is compared over six months, and a detailed analysis is conducted on the cells’ hysteresis and electrical response to varying weather conditions. Although the first cell starts to degrade after a few months of operation, the second one remains remarkably stable, highlighting critical issues with outdoor tracking. Given that the stability of this PSC architecture has already been established under controlled standard conditions for over one year, these exciting findings pave the way for the commercialization of perovskite‐based photovoltaic devices.

Optogenetic therapeutic strategies for diabetes mellitus.

Diabetes mellitus (DM) is a common chronic disease affecting humans globally. It is characterized by abnormally elevated blood glucose levels due to the failure of insulin production or reduction of insulin sensitivity and functionality. Insulin and glucagon-like peptide (GLP)-1 replenishment or improvement of insulin resistance are the two major strategies to treat diabetes. Recently, optogenetics that uses genetically encoded light-sensitive proteins to precisely control cell functions has been regarded as a novel therapeutic strategy for diabetes. Here, we summarize the latest development of optogenetics and its integration with synthetic biology approaches to produce light-responsive cells for insulin/GLP-1 production, amelioration of insulin resistance and neuromodulation of insulin secretion. In addition, we introduce the development of cell encapsulation and delivery methods and smart bioelectronic devices for the in vivo application of optogenetics-based cell therapy in diabetes. The remaining challenges for optogenetics-based cell therapy in the clinical translational study are also discussed.

Impact of Silk-Ionomer Encapsulation on Immune Cell Mechanical Properties and Viability.

Encapsulation of single cells is a powerful technique used in various fields, such as regenerative medicine, drug delivery, tissue regeneration, cell-based therapies, and biotechnology. It offers a method to protect cells by providing cytocompatible coatings to strengthen cells against mechanical and environmental perturbations. Silk fibroin, derived from the silkworm Bombyx mori, is a promising protein biomaterial for cell encapsulation due to the cytocompatibility and capacity to maintain cell functionality. Here, THP-1 cells, a human leukemia monocytic cell line, were encapsulated with chemically modified silk polyelectrolytes through electrostatic layer-by-layer deposition. The effectiveness of the silk nanocoating was assessed using scanning electron microscopy (SEM) and confocal microscopy and on cell viability and proliferation by Alamar Blue assay and live/dead staining. An analysis of the mechanical properties of the encapsulated cells was conducted using atomic force microscopy nanoindentation to measure elasticity maps and cellular stiffness. After the cells were encapsulated in silk, an increase in their stiffness was observed. Based on this observation, we developed a mechanical predictive model to estimate the variations in stiffness in relation to the thickness of the coating. By tuning the cellular assembly and biomechanics, these encapsulations promote systems that protect cells during biomaterial deposition or processing in general.

Mathematical Evaluation of Population Changes of Lactobacillus acidophilus and Bifidobacterium animalis ssp. lactis as Free and Encapsulated Cells in Butter

Growing butter markets, domestically and globally, provide opportunities for value-added variants of butter. Adding probiotics to butter could boosts its bioactivity; however, maintaining probiotic viability during storage is a major challenge. Mathematical analysis of probiotic population changes could help improve our understanding of how probiotics interact with butter and storage conditions. Two strains of probiotics in a 1:1 ratio as free cells or Whey Protein Hydrolysate–Maltodextrin (WPH-MD)-encapsulated cells, Lactobacillus acidophilus ATCC 4356 (LA5) and Bifidobacterium animalis ssp. lactis ATCC 27536 (BB12), were separately mixed into butter at 1% levels. Using analysis of covariance, a mathematical evaluation for probiotic population changes was performed by periodically determining viable counts, resulting in an adjusted R2 value of 0.98 and demonstrating a strong relationship between the dependent variable (log10 counts of probiotics) and independent variables (cell type, temperature of storage, and time of storage). After 21 days of storage, the number of free cells in butter dropped from 7.45 log10 CFU/g to 0.56 log10 CFU/g. On the other hand, it took 63 days for encapsulated cells to achieve 0.80 log10 CFU/g at the same temperature. The same trend persisted at −18 °C, indicating that the WPH-MD encapsulant had a protective effect.

Calcium Alginate Core–Shell Liquid Beads Encapsulated with Microalgae for Wastewater Treatment

Liquid beads are core–shell particles with a liquid core and a solid shell. Calcium alginate liquid beads have been emerging as a promising platform for cell encapsulation. These beads have demonstrated their capability of encapsulating and culturing a wide range of human cells for tissue engineering. However, a significant research gap remains in the application of alginate liquid beads for encapsulating photosynthetic microorganisms. Herein, fast‐growing microalgae strain Chlorella vulgaris is encapsulated into calcium alginate liquid beads to facilitate the removal of nutrients from wastewater, minimizing the risk of eutrophication. Liquid bead‐microalgae systems are prepared, using different calcium ion concentrations as crosslinking ions. It has been thoroughly characterized for their morphologies, cell growth patterns, nutrient removal capabilities, and overall stability throughout the wastewater treatment process, with upflow anaerobic sludge blanket effluent as the wastewater model. The results indicate that the liquid bead‐microalgae system with the highest calcium ion concentration (5%) performs more efficiently, exhibiting a well‐formed crosslinking structure, leading to rapid cell growth with the highest cell density and the most effective removal of nutrients. The findings from this study provide valuable insights for future optimization and upscaling efforts in wastewater treatment systems based on calcium alginate liquid beads.

Improved perovskite photostability via application of TiO2, ZnO and AZO thin films by pulsed laser deposition

The UV-induced degradation of perovskite solar cells has been a barrier to commercialization. Thin film encapsulation represents a promising solution for extending perovskite solar cell lifetimes. Three materials with suitable bandgaps for blocking UV light are identified: TiO2, ZnO and AZO. Herein, the optical properties of TiO2, ZnO and AZO thin films grown by pulsed laser deposition at room-temperature are optimized by varying the oxygen partial pressure between 2, 5 and 20 mTorr during deposition. UV–Vis spectroscopy reveals facile bandgap tuning via the PLD O2 pressure for maximized UV light absorption/reflection. In particular, the TiO2 bandgap is found to narrow with decreasing O2 partial pressure as a result of an increase in oxygen vacancies and Ti3+ interstitials. Conversely, the AZO bandgap widens with decreasing O2 partial pressure, as explained by the Burstein-Moss effect. Finally, ZnO films have stable optical properties at all investigated oxygen pressures. The analysis finds that ZnO, TiO2, and AZO coatings exhibit maximum percentages of absorbed/reflected UV-A light of 72.13 ± 3.05%, 52.30 ± 2.72%, and 52.06 ± 2.20% at 5, 2 and 20 mTorr O2, respectively. Accelerated UV-aging experiments find that the films which screen the most UV light are also most effective in delaying perovskite degradation. A comparison of TiO2, ZnO and AZO photoprotective coatings concludes that ZnO is most suitable for perovskite solar cell encapsulation since it provides a ∼ 50% reduction in UV-degradation without significantly compromising visible light transmittance.

Characterizing an injectable alginate hydrogel as a co‐encapsulating system for beta cells and curcumin in type 1 diabetes therapy

AbstractEncapsulating insulin‐secreting cells within biocompatible hydrogels is a tissue engineering approach for type 1 diabetes treatment. Macroencapsulation is preferred over other encapsulation methods due to its easy implantation and retrieval. However, this treatment has challenges, including the need for invasive surgery for macrocapsule implantation and host response, resulting in fibrotic overgrowth around the implant and subsequent failure of the graft. Herein, an injectable alginate hydrogel, fabricated by different concentrations of as a retarding agent, was applied to avoid surgery. According to characterization tests, hydrogel made by 0.3 M showed a higher swelling ratio and diffusion coefficient, appropriate for the diffusion of nutrients, oxygen, and insulin. It was also stiffer with a lower swelling rate, demonstrating more robust elastic and solid‐like behaviour, suitable for cell attachment. Its small pore size (133.04 ± 53.28 μm), additionally, was essential for inhibiting immunoglobulins penetration. Thus, this hydrogel was used for RIN‐5F cells encapsulation and demonstrated good biocompatibility (>88% viability), and maintained the insulin‐releasing function of cells. Afterward, we co‐encapsulated beta cells with curcumin as an anti‐inflammatory drug and investigated the effect of this agent on cell behaviour in vitro. It was indicated that curcumin did not adversely affect viability and insulin secretion.

Single-Cell Screening through Cell Encapsulation in Photopolymerized Gelatin Methacryloyl

This study evaluated the potential of gelatin methacryloyl (GelMA) for single-cell screening compared to polyethylene glycol diacrylate (PEGDA). GelMA photopolymerized at 1000–2000 mJ/cm2 produced consistent patterns and supported HeLa cell viability. GelMA (5%w/v) facilitated better cell collection within 2 days due to its shape retention. GelMA demonstrated biocompatibility with HeLa cells exhibiting exponential proliferation and biodegradation over 5 days. The average cell displacement over 2 days was 16 µm. Two targeted cell recovery strategies using trypsin were developed: one for adherent cells encapsulated at 800 mJ/cm2, and another for floating cells encapsulated at 800 mJ/cm2, enabling the selective removal of unwanted cells. These findings suggest GelMA as a promising biomaterial for single-cell screening applications, offering advantages over PEGDA in cell encapsulation and targeted recovery.

Fully synthetic, tunable poly(α-amino acids) as the base of bioinks curable by visible light

Bioinks play a crucial role in tissue engineering, influencing mechanical and chemical properties of the printed scaffold as well as the behavior of encapsulated cells. Recently, there has been a shift from animal origin materials to their synthetic alternatives. In this context, we present here bioinks based on fully synthetic and biodegradable poly(α,L-amino acids) (PolyAA) as an alternative to animal-based gelatin methacrylate (Gel-Ma) bioinks. Additionally, we first reported the possibility of the visible light photoinitiated incorporation of the bifunctional cell adhesive RGD peptide into the PolyAA hydrogel matrix. The obtained hydrogels are shown to be cytocompatible, and their mechanical properties closely resemble those of gelatin methacrylate-based scaffolds. Moreover, combining the unique properties of PolyAA-based bioinks, the photocrosslinking strategy, and the use of droplet-based printing allows the printing of constructs with high shape fidelity and structural integrity from low-viscosity bioinks without using any sacrificial components. Overall, presented PolyAA-based materials are a promising and versatile toolbox that extends the range of bioinks for droplet bioprinting.

Cell-adhesive double network self-healing hydrogel capable of cell and drug encapsulation: New platform to construct biomimetic environment with bottom-up approach

This study presents the development and characterization of a novel double-network self-healing hydrogel based on N-carboxyethyl chitosan (CEC) and oxidized dextran (OD) with the incorporation of crosslinked collagen (CEC-OD/COL-GP) to enhance its biological and physicochemical properties. The hydrogel formed via dynamic imine bond formation exhibited efficient self-healing within 30 min, and a compressive modulus recovery of 92 % within 2 h. In addition to its self-healing ability, CEC-OD/COL-GP possesses unique physicochemical characteristics including transparency, injectability, and adhesiveness to various substrates and tissues. Cell encapsulation studies confirmed the biocompatibility and suitability of the hydrogel as a cell-culture scaffold, with the presence of a collagen network that enhances cell adhesion, spreading, long-term cell viability, and proliferation. Leveraging their unique properties, we engineered assemblies of self-healing hydrogel modules for controlled spatiotemporal drug delivery and constructed co-culture models that simulate angiogenesis in tumor microenvironments. Overall, the CEC-OD/COL-GP hydrogel is a versatile and promising material for biomedical applications, offering a bottom-up approach for constructing complex structures with self-healing capabilities, controlled drug release, and support for diverse cell types in 3D environments. This hydrogel platform has considerable potential for advancements in tissue engineering and therapeutic interventions.

Evaluation of Alginate Hydrogel Microstrands for Stromal Cell Encapsulation and Maintenance.

Mesenchymal stromal cells (MSCs) have displayed potential in regenerating organ function due to their anti-fibrotic, anti-inflammatory, and regenerative properties. However, there is a need for delivery systems to enhance MSC retention while maintaining their anti-fibrotic characteristics. This study investigates the feasibility of using alginate hydrogel microstrands as a cell delivery vehicle to maintain MSC viability and phenotype. To accommodate cell implantation needs, we invented a Syringe-in-Syringe approach to reproducibly fabricate microstrands in small numbers with a diameter of around 200 µm and a porous structure, which would allow for transporting nutrients to cells by diffusion. Using murine NIH 3T3 fibroblasts and primary embryonic 16 (E16) salivary mesenchyme cells as primary stromal cell models, we assessed cell viability, growth, and expression of mesenchymal and fibrotic markers in microstrands. Cell viability remained higher than 90% for both cell types. To determine cell number within the microstrands prior to in vivo implantation, we have further optimized the alamarBlue assay to measure viable cell growth in microstrands. We have shown the effect of initial cell seeding density and culture period on cell viability and growth to accommodate future stromal cell delivery and implantation. Additionally, we confirmed homeostatic phenotype maintenance for E16 mesenchyme cells in microstrands.

Versatile xanthan gum-based support bath material compatible with multiple crosslinking mechanisms: rheological properties, printability, and cytocompatibility study

Extrusion-based bioprinting is a promising technology for the fabrication of complex three-dimensional (3D) tissue-engineered constructs. To further improve the printing accuracy and provide mechanical support during the printing process, hydrogel-based support bath materials have been developed. However, the gel structure of some support bath materials can be compromised when exposed to certain bioink crosslinking cues, hence their compatibility with bioinks can be limited. In this study, a xanthan gum-based composite support material compatible with multiple crosslinking mechanisms is developed. Different support bath materials can have different underlying polymeric structures, for example, particulate suspensions and polymer solution with varying supramolecular structure) and these properties are governed by a variety of different intermolecular interactions. However, common rheological behavior can be expected because they have similar demonstrated performance and functionality. To provide a detailed exploration/identification of the common rheological properties expressed by different support bath materials from a unified perspective, benchmark support bath materials from previous studies were prepared. A comparative rheological study revealed both the structural and shear behavior characteristics shared by support bath materials, including yield stress, gel complex moduli, shear-thinning behavior, and self-healing properties. Gel structural stability and functionality of support materials were tested in the presence of various crosslinking stimuli, confirming the versatility of the xanthan-based support material. We further investigated the effect of support materials and the diameter of extrusion needles on the printability of bioinks to demonstrate the improvement in bioink printability and structural integrity. Cytotoxicity and cell encapsulation viability tests were carried out to confirm the cell compatibility of the xanthan gum-based support bath material. We propose and demonstrate the versatility and compatibility of the novel support bath material and provide detailed new insight into the essential properties and behavior of these materials that serve as a guide for further development of support bath-based 3D bioprinting.

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.

Chitosan-PNIPAM Thermogel Associated with Hydrogel Microspheres as a Smart Formulation for MSC Injection.

Regenerative medicine based on cell therapy has emerged as a promising approach for the treatment of various medical conditions. However, the success of cell therapy heavily relies on the development of suitable injectable hydrogels that can encapsulate cells and provide a conducive environment for their survival, proliferation, and tissue regeneration. Herein, we address the medical need for cyto- and biocompatible injectable hydrogels by reporting on the synthesis of a hydrogel-forming thermosensitive copolymer. The copolymer was synthesized by grafting poly(N-isopropylacrylamide-co-carboxymethyl acrylate) (PNIPAM-COOH) onto chitosan through amide coupling. This chemical modification resulted in the formation of hydrogels that exhibit a sol-gel transition with an onset at approximately 27 °C, making them ideal for use in injectable applications. The hydrogels supported the survival and proliferation of cells for several days, which is critical for cell encapsulation. Furthermore, the study evaluates the addition of collagen/chitosan hybrid microspheres to support the adhesion of mesenchymal stem cells within the hydrogels. Altogether, these results demonstrate the potential of the PNIPAM-chitosan thermogel for cell encapsulation and its possible applications in regenerative medicine.

Alternative Therapies in Transplantology as a Promising Perspective in Medicine.

Despite continuous and rapid progress in the transplantation of cells, tissues, and organs, many patients die before receiving them. This is because of an insufficient number of donors, which leads to a significant disproportion between the need for donors and their availability. This review aims to present the possibilities offered by alternative therapies. We use the term "functional transplantology" to describe such alternative methods of transplantation that could help change the current state of transplantation medicine. Its purpose is not to replace a defective or removed organ with another but to replace its functions using complementary biological, mechanical, or biomechanical structures or devices. Implementation of many innovative solutions shown in the work for clinical applications is already a fact. In the case of others, it should be considered a future vision. We hope that the role of a defective or damaged tissue or a group of tissues will be taken over by different structures that are functionally complementary with the organ being substituted. Undoubtedly, developing the described methods based on functional transplantology will change the face of transplantation medicine. Thus, we show current trends and new directions of thinking and actions in transplantation medicine that combine technology and transplantology. The review considers the latest technologies, including 3D bioprinting, nanotechnology, cell encapsulation, and organoids. We discuss not only the advantages of new approaches but also the limitations and challenges that must be overcome to achieve significant progress in transplantation. That is the only option to provide a safe and efficient way of improving the quality of life of many patients.

Measuring cell proliferation in bioprinting research

Tissue-like constructs, intended for application in tissue engineering and regenerative medicine, can be produced by three-dimensional (3D) bioprinting of cells in hydrogels. It is essential that the viability and proliferation of the encapsulated cells can be reliably determined. Methods currently used to evaluate cell proliferation, such as quantification of DNA and measurement of metabolic activity, have been developed for application in 2D cultures and might not be suitable for bioinks. In this study, human fibroblasts were either cast or printed in gelatin methacryloyl (GelMA) or sodium alginate hydrogels and cell proliferation was assessed by AlamarBlue, PicoGreen and visual cell counts. Comparison of data extrapolated from standard curves generated from 2D cultures and 3D hydrogels showed potential inaccuracies. Moreover, there were pronounced discrepancies in cell numbers obtained from these assays; the different bioinks strongly influenced the outcomes. Overall, the results indicate that more than one method should be applied for better assessment of cell proliferation in bioinks.

Modelling the non-isothermal curing kinetics of peroxide crosslinking polyolefin copolymers for photovoltaic module lamination

This study presents a model for determining the non-isothermal curing kinetics of peroxide crosslinking polyolefin copolymers used for encapsulation of silicon solar cells in photovoltaic modules. Therefore, rheological data of ethylene vinyl acetate copolymer (EVA) and polyolefin elastomer (POE) were analyzed. The curing kinetics were described assuming a temperature dependent Arrhenius rate coefficient and implementing a reaction rate model. Validation was performed under isothermal and non-isothermal conditions. An excellent agreement of experimental and model data was ascertained. The model was used to determine the non-isothermal crosslinking conversion during lamination of EVA or POE based photovoltaic mini-modules. Temperatures were tracked by positioning seven sensors within the mini-modules. Moreover, a thermal simulation model was implemented. Also on module level, the experimental results corroborated the simulated data. A lamination temperature of 150 °C led to insufficient curing of POE based modules. Similar conversion rates were achieved for EVA and POE encapsulants at 150 and 160 °C, respectively.

Bio Artificial Pancreas - Encapsulation of Human Pancreatic Islet Cells Using Calcium Alginate Micro Beads for the Use in the Clinical Therapy

Bio Artificial Pancreas - Encapsulation of Human Pancreatic Islet Cells Using Calcium Alginate Micro Beads for the Use in the Clinical Therapy