Collagen short nanofiber-embedded chondroitin sulfate-hyaluronic acid nanocomposite: A cartilage-mimicking in situ-forming hydrogel with fine-tuned properties

In situ-forming hydrogels that possess the ability to be injected in a less invasive manner and mimic the biochemical composition and microarchitecture of the native cartilage extracellular matrix are desired for cartilage tissue engineering. Besides, gelation time and stiffness of the hydrogel are two interdependent factors that affect cells' distribution and fate and hence need to be optimized. This study presented a bioinspired in situ-forming hydrogel composite of hyaluronic acid (HA), chondroitin sulfate (CS), and collagen short nanofiber (CSNF). HA and CS were functionalized with aldehyde and amine groups to form a gel through a Schiff-base reaction. CSNF was fabricated via electrospinning, followed by fragmentation by ultrasonics. Gelation time (11-360 s) and compressive modulus (1.4-16.2 kPa) were obtained by varying the concentrations of CS, HA, CSNFs, and CSNFs length. The biodegradability and biocompatibility of the hydrogels with varying gelation and stiffness were also assessed in vitro and in vivo. At three weeks, the assessment of hydrogels' chondrogenic differentiation also yields varying levels of chondrogenic differentiation. The subcutaneous implantation of the hydrogels in a mouse model indicated no severe inflammation. Results demonstrated that the injectable CS/HA@CSNF hydrogel was a promising hydrogel for tissue engineering and cartilage regeneration.

The Effect of Multilayered Electrospun PLLA Nanofibers Coated with Human Amnion or Bladder ECM Proteins on Epithelialization and Smooth Muscle Regeneration in the Rabbit Bladder

Nanofibrous scaffolds have attracted much attention in bladder reconstruction approaches due to their excellent mechanical properties. In addition, their biological properties can be improved by combination with biological materials. Taking into account the advantages of nanofibrous scaffolds and decellularized extracellular matrix (dECM) in tissue engineering, scaffolds of poly-L-lactic acid (PLLA) coated with decellularized human amnion membrane (hAM) or sheep bladder (SB)-derived ECM proteins are developed (amECM-coated PLLA and sbECM-coated PLLA, respectively). The bladder regenerative potential of modified electrospun PLLA scaffolds is investigated in rabbits. The presence of ECM proteins is confirmed on the nanofibers' surface. Coating the surface of the PLLA nanofibers improves cell adhesion and proliferation. Histological and immunohistochemical evaluations show that rabbits subjected to cystoplasty with a multilayered PLLA scaffold show de novo formation and maturation of the multilayered urothelial layer. However, smooth muscle bundles (myosin heavy chain [MHC] and α-smooth muscle actin [α-SMA] positive) are detected only in ECM-coated PLLA groups. All groups show no evidence of a diverticulumor fistula in the urinary bladder. These results suggest that the biofunctionalization of electrospun PLLA nanofibers with ECM proteins can be a promising option for bladder tissue engineering. Furthermore, hAM can also replace animal-sourced ECM proteins in bladder tissue regeneration approaches.

GelMA-catechol coated FeHAp nanorods functionalized nanofibrous reinforced bio-instructive and mechanically robust composite hydrogel scaffold for bone tissue engineering

Critical bone defects complicate tissue graft-based surgeries, raising healthcare expenditures and underscoring scaffold-based tissue-engineering strategies to support bone reconstruction. Our study highlighted that the phase-compatible combination of inorganic nanorods, nanofibers, and hydrogels is promising for developing biomimetic and cell-instructive scaffolds since the bone matrix is a porous organic/inorganic composite. In brief, methacrylated gelatin (GelMA) was reacted with dopamine to form catechol-modified GeLMA (GelMA-C). The GelMA-C was nanocoated onto an iron-doped hydroxyapatite (FeHAp) nanorod via metal-catechol network coordination. The modified nanorod (FeHAp@GelMA-C) was loaded onto GelMA-based nanofibers. The nanorods loaded pre-fibers were electrospun onto GelMA solution and photochemically crosslinked to fabricate a fiber-reinforced hydrogel. The structural, mechanical, physicochemical, biocompatibility, swelling properties, osteogenic potential, and bone remodelling potential (using rat femoral defect model) of modified nanorods, simple hydrogel, and nanorod-loaded fiber-reinforced hydrogel were studied. The results supported that the interface interaction between GelMA-C/nanorods, nanorods/nanofibers, nanorods/hydrogels, and nanofiber/hydrogels significantly improved the microstructural and mechanical properties of the scaffold. Compared to pristine hydrogel, the nanorod-loaded fiber-reinforced scaffold better supported cellular responses, osteogenic differentiation, matrix mineralization, and accelerated bone regeneration. The nanorod-loaded fiber-reinforced hydrogel proved more biomimetic and cell-instructive for guided bone reconstruction.

The effect of conductive aligned fibers in an injectable hydrogel on nerve tissue regeneration

Injectable hydrogels are a promising treatment option for nervous system injuries due to the difficulty to replace lost cells and nervous factors but research on injectable conductive hydrogels is limited and these scaffolds have poor electromechanical properties. This study developed a chitosan/beta-glycerophosphate/salt hydrogel and added conductive aligned nanofibers (polycaprolactone/gelatin/single-wall carbon nanotube (SWCNT)) for the first time and inspired by natural nerve tissue to improve their biochemical and biophysical properties. The results showed that the degradation rate of hydrogels is proportional to the regrowth of axons and these hydrogels' mechanical (hydrogels without nanofibers or SWCNTs and hydrogels containing these additions have the same Young's modulus as the brain and spinal cord or peripheral nerves, respectively) and electrical properties, and the interconnective structure of the scaffolds have the ability to support cells.

Magnetic Nanofibrous Hydrogels for Dynamic Control of Stem Cell Differentiation

The extracellular matrix in tissue consists of complex heterogeneous soft materials with hierarchical structure and dynamic mechanical properties dictating cell and tissue level function. In many natural matrices, there are nanofibrous structures that serve to guide cell activity and dictate the form and function of tissue. Synthetic hydrogels with integrated nanofibers can mimic the structural properties of native tissue; however, model systems with dynamic mechanical properties remain elusive. Here we demonstrate modular nanofibrous hydrogels that can be reversibly stiffened in response to applied magnetic fields. Iron oxide nanoparticles were incorporated into gelatin nanofibers through electrospinning, followed by chemical stabilization and fragmentation. These magnetoactive nanofibers can be mixed with virtually any hydrogel material and reversibly stiffen the matrix at a low fiber content (≤3%). In contrast to previous work, where a large quantity of magnetic material disallowed cell encapsulation, the low nanofiber content allows matrix stiffening with cells in 3D. Using adipose derived stem cells, we show how nanofibrous matrices are beneficial for both osteogenesis and adipogenesis, where stiffening the hydrogel with applied magnetic fields enhances osteogenesis while discouraging adipogenesis. Skeletal myoblast progenitors were used as a model of tissue morphogenesis with matrix stiffening augmenting myogenesis and multinucleated myotube formation. The ability to reversibly stiffen fibrous hydrogels through magnetic stimulation provides a useful tool for studying nanotopography and dynamic mechanics in cell culture, with a scope for stimuli responsive materials for tissue engineering.

Three-dimensional biomimetic reinforced chitosan/gelatin composite scaffolds containing PLA nano/microfibers for soft tissue engineering application

In the current study, we successfully prepared chitosan/gelatin composite scaffolds reinforced by centrifugally spun polylactic acid (PLA) chopped nano/microfibers (PLA-CFs). Herein, different amounts of PLA-CFs (0 %, 1 %, 2 %, 3 %, and 4 % w/v) dispersed in chitosan/gelatin solution were used. Morphological characterization of prepared scaffolds revealed that at the initial stage of adding PLA-CFs, the chopped fibers were localized at the wall of the pores; however, as the fiber load increased, aggregations of chopped-fibers could be seen. Also, mechanical evaluation of scaffolds in terms of compression and tensile mode showed that samples reinforced with 2 % PLA-CFs had enhanced mechanical properties. Indeed, its tensile strength increased from 123.8 to 247.2 kPa for dry and 18.9 to 48.6 kPa for wet conditions. Furthermore, the tensile modulus associated with both conditions increased from 2.99 MPa and 44.5 kPa to 6.43 MPa and 158.4 kPa, respectively. The results of cell culture studies also confirmed that the prepared composite scaffold exhibited appropriate biocompatibility, cell proliferation and migration. The cell infiltration study of the samples revealed that scaffolds reinforced with 2 % PLA-CFs had significantly better cell penetration and distribution compared with the control ones on both days (7 and 14).

Hydrogels for Salivary Gland Tissue Engineering

Mimicking the complex architecture of salivary glands (SGs) outside their native niche is challenging due their multicellular and highly branched organization. However, significant progress has been made to recapitulate the gland structure and function using several in vitro and ex vivo models. Hydrogels are polymers with the potential to retain a large volume of water inside their three-dimensional structure, thus simulating extracellular matrix properties that are essential for the cell and tissue integrity. Hydrogel-based culture of SG cells has seen a tremendous success in terms of developing platforms for cell expansion, building an artificial gland, and for use in transplantation to rescue loss of SG function. Both natural and synthetic hydrogels have been used widely in SG tissue engineering applications owing to their properties that support the proliferation, reorganization, and polarization of SG epithelial cells. While recent improvements in hydrogel properties are essential to establish more sophisticated models, the emphasis should still be made towards supporting factors such as mechanotransduction and associated signaling cues. In this concise review, we discuss considerations of an ideal hydrogel-based biomaterial for SG engineering and their associated signaling pathways. We also discuss the current advances made in natural and synthetic hydrogels for SG tissue engineering applications.

Fabrication and investigating in vivo wound healing property of coconut oil loaded nanofiber/hydrogel hybrid scaffold

Obtaining a sustainable drug delivery system is a challenging issue in biomedical science. This became even more important in the wound regeneration process due to its long treatment process. In this study, the calcium alginate (CaAlg) hydrogel is coated on the surface of polycaprolactone (PCL)/gelatin (Gel) nanofibers containing coconut oil (CO) using the impregnation method. The physical, chemical, and morphological properties of produced samples are investigated using different characterization techniques to verify the influence of hydrogel. Water contact angle, swelling ratio, and water vapor permeability measurements are used to evaluate the effect of hydrogel on the hydrophilicity of the proposed system. The cell viability test showed that the nanocomposite hydrogel is biocompatible and could improve wound healing. According to drug release studies, hydrogel addition to the nanofiber system plays an essential role in controlling CO release rate in the first 250 h. In vivo studies also indicated faster skin regeneration.

Wet Electrospun Nanofibers-Fortified Gelatin/Alginate-Based Nanocomposite as a Single-Dose Biomimicking Skin Substitute

We report the development and evaluation of a series of well-designed single-dose extracellular matrix (ECM)-mimicking nanofibers (NFs)-reinforced hydrogel (HG)-based skin substitute for wound healing. The HG matrix of the proposed skin substitute is composed of gelatin (GE) and sodium alginate (SA), and incorporates hyaluronic acid (HA) as a key component of the natural ECM, as well as the antimicrobial Punica granatum extract (PE). This HG nanocomposite was cross-linked by the biocompatible N-(3-(dimethylamino)propyl)-N'-ethylcarbodiimide hydrochloride (EDC) cross-linker, and was reinforced with fragmented trans-ferulic acid (FA)-loaded cellulose acetate/polycaprolactone (PCL/CA) NFs. The NFs were obtained via wet electrospinning into a poly(vinyl alcohol) (PVA) coagulating solution to closely resemble the porous structure of the ECM fibers, which facilitates cell migration, attachment, and proliferation. The proposed design of the skin substitute allows adjustable mechanical characteristics and outstanding physical properties (swelling and biodegradability), as well as an excellent porous microstructure. The developed skin substitutes were characterized using Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and electron microscopy. In addition, the biodegradability, biocompatibility, bioactivity, mechanical, and in vitro drug release characteristics were investigated. Moreover, an in vivo excisional full-thickness defect model was conducted to assess skin regeneration and healing effectiveness. The average diameters of the plain and FA-loaded NFs are 210 ± 12 nm and 452 ± 25 nm, respectively. The developed ECM-mimicking skin substitutes demonstrated good antibacterial activity, free-radical scavenging activity, cytocompatibility, porosity, water absorption ability, and good biodegradability. In vivo application of the ECM-mimicking skin substitutes revealed their excellent wound-healing activity and their suitability for single-dose treatment of deep wounds with reducing the wound diameter to 0.95 mm after 15 days of treatment. Moreover, the histological investigation of the wound area demonstrated that the applied skin substitutes have not only enhanced the wound healing progress, but also can participate in improving the quality of the regenerated skin in the treated area via facilitating collagen fibers regeneration and deposition.

Current hydrogel advances in physicochemical and biological response-driven biomedical application diversity

Hydrogel is a type of versatile platform with various biomedical applications after rational structure and functional design that leverages on material engineering to modulate its physicochemical properties (e.g., stiffness, pore size, viscoelasticity, microarchitecture, degradability, ligand presentation, stimulus-responsive properties, etc.) and influence cell signaling cascades and fate. In the past few decades, a plethora of pioneering studies have been implemented to explore the cell-hydrogel matrix interactions and figure out the underlying mechanisms, paving the way to the lab-to-clinic translation of hydrogel-based therapies. In this review, we first introduced the physicochemical properties of hydrogels and their fabrication approaches concisely. Subsequently, the comprehensive description and deep discussion were elucidated, wherein the influences of different hydrogels properties on cell behaviors and cellular signaling events were highlighted. These behaviors or events included integrin clustering, focal adhesion (FA) complex accumulation and activation, cytoskeleton rearrangement, protein cyto-nuclei shuttling and activation (e.g., Yes-associated protein (YAP), catenin, etc.), cellular compartment reorganization, gene expression, and further cell biology modulation (e.g., spreading, migration, proliferation, lineage commitment, etc.). Based on them, current in vitro and in vivo hydrogel applications that mainly covered diseases models, various cell delivery protocols for tissue regeneration and disease therapy, smart drug carrier, bioimaging, biosensor, and conductive wearable/implantable biodevices, etc. were further summarized and discussed. More significantly, the clinical translation potential and trials of hydrogels were presented, accompanied with which the remaining challenges and future perspectives in this field were emphasized. Collectively, the comprehensive and deep insights in this review will shed light on the design principles of new biomedical hydrogels to understand and modulate cellular processes, which are available for providing significant indications for future hydrogel design and serving for a broad range of biomedical applications.

Bioprinting a thick and cell-laden partially oxidized alginate-gelatin scaffold with embedded micro-channels as future soft tissue platform

Despite all the advancements in tissue engineering, one of the unsolved challenges is the mass transfer limitation. Therefore, the subject of pre-vascularization in the engineered tissues gets more attention to avoid necrotic core formation. In this study, we considered a design for interconnected channels with a muscle tissue-like structure, in silico and in vitro. A sequence of simple steps make it possible for us to use the same material, gelatin, as both a sacrificial material and one of the main components of the scaffold simultaneously. We defined a new approach to quantify the repeatability of a new combination of hydrogels (Partially Oxidized Alginate + Gelatin) for extrusion-based bioprinting. Additionally, the mechanical properties, hydrogel porosity, degradation time, and swelling ratio were also evaluated. Based on all these test results, the scaffold with the optimum properties was chosen for the bioprinting of adipose derived mesenchymal stem cells (ADMSCs) in the scaffolds with and without the channels. This bioprinted scaffold with microchannels showed promising mimicry of the microenvironment, leading to higher survival and proliferation rates of the cells by up to 250%. Based on these results, it has the potential to serve as a platform for further research in vascularization, healthy/disease modelling, and stem cell differentiation.

Preparation of gelatin-based hydrogels with tunable mechanical properties and modulation on cell-matrix interactions

Natural polymer material-based hydrogels normally show inferior mechanical stability and strength to bear large deformation and cyclic loading, therefore their applications in food, biomedical and tissue engineering fields are greatly limited. In this study, gelatin-based hydrogels with remarkable stability, as well as tunable mechanical properties, were prepared via a facile method known as the Hofmeister effect. The higher concentration of potassium sulfatesolution resulted in more dehydration and molecular chain folding, thus the treated hydrogels showed significantly improved tensile and compressive modulus, and decreased equilibrium swelling ratio, as revealed by scanning electron microscopy (SEM), Fourier transform infraredspectroscopy (FTIR), and mechanical tests, etc. Additionally, the reinforced hydrogels were recoverable and biocompatible to modulate the proliferation behavior of human umbilical vein endothelial cells. In conclusion, this paper provides a facile reference for tuning mechanical properties of gelatin-based hydrogels and cell-hydrogel interactions, which show potential capacity in tissue engineering and biomedical fields.

Scaffold-mediated CRISPR-Cas9 delivery system for acute myeloid leukemia therapy

Leukemia stem cells (LSCs) sustain the disease and contribute to relapse in acute myeloid leukemia (AML). Therapies that ablate LSCs may increase the chance of eliminating this cancer in patients. To this end, we used a bioreducible lipidoid-encapsulated Cas9/single guide RNA (sgRNA) ribonucleoprotein [lipidoid nanoparticle (LNP)-Cas9 RNP] to target the critical gene interleukin-1 receptor accessory protein (IL1RAP) in human LSCs. To enhance LSC targeting, we loaded LNP-Cas9 RNP and the chemokine CXCL12α onto mesenchymal stem cell membrane-coated nanofibril (MSCM-NF) scaffolds mimicking the bone marrow microenvironment. In vitro, CXCL12α release induced migration of LSCs to the scaffolds, and LNP-Cas9 RNP induced efficient gene editing. IL1RAP knockout reduced LSC colony-forming capacity and leukemic burden. Scaffold-based delivery increased the retention time of LNP-Cas9 in the bone marrow cavity. Overall, sustained local delivery of Cas9/IL1RAP sgRNA via CXCL12α-loaded LNP/MSCM-NF scaffolds provides an effective strategy for attenuating LSC growth to improve AML therapy.

Alginate-magnetic short nanofibers 3D composite hydrogel enhances the encapsulated human olfactory mucosa stem cells bioactivity for potential nerve regeneration application

The design of 3D hydrogel constructs to elicit highly controlled cell response is a major field of interest in developing tissue engineering. The bioactivity of encapsulated cells inside pure alginate hydrogel is limited by its relatively inertness. Combining short nanofibers within a hydrogel serves as a promising method to develop a cell friendly environment mimicking the extracellular matrix. In this paper, we fabricated alginate hydrogels incorporating different magnetic short nanofibers (M.SNFs) content for olfactory ecto-mesenchymal stem cells (OE-MSCs) encapsulation. Wet-electrospun gelatin and superparamagnetic iron oxide nanoparticles (SPIONs) nanocomposite nanofibers were chopped using sonication under optimized conditions and subsequently embedded in alginate hydrogels. The storage modulus of hydrogel without M.SNFs as well as with 1 and 5 mg/mL of M.SNFs were in the range of nerve tissue. For cell encapsulation, OE-MSCs were used as a new hope for neuronal regeneration due to their neural crest origin. Resazurin analyses and LIVE/DEAD staining confirmed that the composite hydrogels containing M.SNFs can preserve the cell viability after 7 days. Moreover, the proliferation rate was enhanced in M.SNF/hydrogels compared to alginate hydrogel. The presence of SPIONs in the short nanofibers can accelerate neural-like differentiation of OE-MSCs rather than the sample without SPIONs.

Coaxial Electrospun Nanofibers with Different Shell Contents to Control Cell Adhesion and Viability

Electrospun nanofibers are widely employed as cell culture matrices because their biomimetic structures resemble a natural extracellular matrix. However, due to the limited cell infiltration into nanofibers, three-dimensional (3D) construction of a cell matrix is not easily accomplished. In this study, we developed a method for the partial digestion of a nanofiber into fragmented nanofibers composed of gelatin and polycaprolactone (PCL). The PCL shells of the coaxial fragments were subsequently removed with different concentrations of chloroform to control the remaining PCL on the shell. The swelling and exposure of the gelatin core were manipulated by the remaining PCL shells. When cells were cultivated with the fragmented nanofibers, they were spontaneously assembled on the cell sheets. The cell adhesion and proliferation were significantly affected by the amount of PCL shells on the fragmented nanofibers.

Composite Hydrogel of Methacrylated Hyaluronic Acid and Fragmented Polycaprolactone Nanofiber for Osteogenic Differentiation of Adipose-Derived Stem Cells

Composite hydrogels with electrospun nanofibers (NFs) have recently been used to mimic the native extracellular matrix. In this study, composite hydrogels of methacrylated hyaluronic acid containing fragmented polycaprolactone NFs were used for bone tissue engineering. The composite (NF/hydrogel) was crosslinked under ultraviolet (UV) light. The incorporation of fragmented polycaprolactone NFs increased the compression modulus from 1762.5 to 3122.5 Pa. Subsequently, adipose-derived stem cells incorporated into the composite hydrogel exhibited a more stretched and elongated morphology and osteogenic differentiation in the absence of external factors. The mRNA expressions of osteogenic biomarkers, including collagen 1 (Col1), alkaline phosphatase, and runt-related transcription factor 2, were 3-5-fold higher in the composite hydrogel than in the hydrogel alone. In addition, results of the protein expression of Col1 and alizarin red staining confirmed osteogenic differentiation. These findings suggest that our composite hydrogel provides a suitable microenvironment for bone tissue engineering.

Protein-reactive nanofibrils decorated with cartilage-derived decellularized extracellular matrix for osteochondral defects

Cartilage defect is difficult to heal due to its avascular properties. Implantation of mesenchymal stem cell is one of the most promising approach for regenerating cartilage defects. Here we prepared polymeric nanofibrils decorated with cartilage-derived decellularized extracellular matrix (dECM) as a chondroinductive scaffold material for cartilage repair. To fabricate nanofibrils, eletrospun PCL nanofibers were fragmented by subsequent mechanical and chemical process. The nanofibrils were surface-modified with poly(glycidyl methacrylate) (PGMA@NF) via surface-initiated atom transfer radical polymerization (SI-ATRP). The epoxy groups of PGMA@NF were subsequently reacted with dECM prepared from bovine articular cartilage. Therefore, the cartilage-dECM-decorated nanofibrils structurally and biochemically mimic cartilage-specific microenvironment. Once adipose-derived stem cells (ADSCs) were self-assembled with the cartilage-dECM-decorated nanofibrils by cell-directed association, they exhibited differentiation hallmarks of chondrogenesis without additional biologic additives. ADSCs in the nanofibril composites significantly increased expression of chondrogenic gene markers in comparison to those in pellet culture. Furthermore, ADSC-laden nanofibril composites filled the osteochondral defects compactly due to their clay-like texture. Thus, the ADSC-laden nanofibril composites supported the long-term regeneration of 12 weeks without matrix loss during joint movement. The defects treated with the ADSC-laden PGMA@NF significantly facilitated reconstruction of their cartilage and subchondral bone ECM matrices compared to those with ADSC-laden nanofibrils, non-specifically adsorbing cartilage-dECM without surface decoration of PGMA.

Michael-Type Addition of Gelatin on Electrospun Nanofibrils for Self-Assembly of Cell Sheets Composed of Human Dermal Fibroblasts

To facilitate cell sheet formation of human dermal fibroblasts, gelatin moieties were chemically decorated onto the surface of electrospun nanofibrils (NFs). Poly(caprolactone) [PCL] was electrospun onto fibrous meshes and then fragmented into nanofibrils by optimized milling and hydrolysis. After aminolysis of the NFs, methacrylated gelatin (GelMA) was reacted via Michael-type addition with the surface-exposed amines of the aminolyzed NFs (ahPCL NFs). GelMA was immobilized on the ahPCL NFs. Analysis of ahPCL NFs and native NFs conducted using X-ray photoelectron spectroscopy confirmed that gelatin was chemically conjugated onto the NFs. Human dermal fibroblasts (HDF) and the decorated NFs were self-assembled into cell sheets, and cells in the matrix showed highly spreading morphology by confocal microscopy. Our results indicate that the degree of cell spreading and cellular viability was much higher in the presence of GelMA immobilized in ahPCL NFs.

Nano-fibre Integrated Microcapsules: A Nano-in-Micro Platform for 3D Cell Culture

Nano-in-micro (NIM) system is a promising approach to enhance the performance of devices for a wide range of applications in disease treatment and tissue regeneration. In this study, polymeric nanofibre-integrated alginate (PNA) hydrogel microcapsules were designed using NIM technology. Various ratios of cryo-ground poly (lactide-co-glycolide) (PLGA) nanofibres (CPN) were incorporated into PNA hydrogel microcapsule. Electrostatic encapsulation method was used to incorporate living cells into the PNA microcapsules (~500 µm diameter). Human liver carcinoma cells, HepG2, were encapsulated into the microcapsules and their physio-chemical properties were studied. Morphology, stability, and chemical composition of the PNA microcapsules were analysed by light microscopy, fluorescent microscopy, scanning electron microscopy (SEM), Fourier-Transform Infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The incorporation of CPN caused no significant changes in the morphology, size, and chemical structure of PNA microcapsules in cell culture media. Among four PNA microcapsule products (PNA-0, PNA-10, PNA-30, and PNA-50 with size 489 ± 31 µm, 480 ± 40 µm, 473 ± 51 µm and 464 ± 35 µm, respectively), PNA-10 showed overall suitability for HepG2 growth with high cellular metabolic activity, indicating that the 3D PNA-10 microcapsule could be suitable to maintain better vitality and liver-specific metabolic functions. Overall, this novel design of PNA microcapsule and the one-step method of cell encapsulation can be a versatile 3D NIM system for spontaneous generation of organoids with in vivo like tissue architectures, and the system can be useful for numerous biomedical applications, especially for liver tissue engineering, cell preservation, and drug toxicity study.

Coaxial Hydro-Nanofibrils for Self-Assembly of Cell Sheets Producing Skin Bilayers

Bilayered cell sheets were fabricated with coaxial hydro-nanofibrils for three-dimensional (3D) cultivation in a biomimetic environment. Polycaprolactone (PCL) was electrospun and hydrolyzed to release fragmented nanofibrils (NF) in an alkaline condition. Methacrylated gelatin (GelMA) was adsorbed and phototethered on the surface of the fibrils to prepare coaxial NF composed of hydrophilic shells and hydrophobic cores. GelMA layers on the NF were characterized by X-ray photoemission spectroscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The GelMA showed higher decoration level on NF compared to that on native gelatin. GelMA-decorated NF significantly enhanced cell proliferation rate and phenotypic expression of human dermal fibroblasts when spontaneous formation of cell sheets was observed for 7 days. HaCaT cells were layered on top of the fibroblast sheets and further cultivated in air-water interfaces to prepare bilayered skin sheets. After 21 days of incubation, the top layers of the bilayered sheets showed higher expression of pan-keratin, and the dermal cells showed higher proliferation in the GelMA-decorated NF.