Evaluation of Polyethylene Glycol Diacrylate-Polycaprolactone Scaffolds for Tissue Engineering Applications

Surface-modified injectable poly(ethylene-glycol) diacrylate-based cryogels for localized gene delivery

Lentiviral transduction is widely used in research, has shown promise in clinical trials involving gene therapy and has been approved for CAR-T cell immunotherapy. However, most modifications are doneex vivoand rely on systemic administration of large numbers of transduced cells for clinical applications. A novel approach utilizingin situbiomaterial-based gene delivery can reduce off-target side effects while enhancing effectiveness of the manipulation process. In this study, poly(ethylene glycol) diacrylate (PEGDA)-based scaffolds were developed to enablein situlentivirus-mediated transduction. Compared to other widely popular biomaterials, PEGDA stands out due to its robustness and cost-effectiveness. These scaffolds, prepared via cryogelation, are capable of flowing through surgical needles in bothin vitroandin vivoconditions, and promptly regain their original shape. Modification with poly(L-lysine) (PLL) enables lentivirus immobilization while interconnected macroporous structure allows cell infiltration into these matrices, thereby facilitating cell-virus interaction over a large surface area for efficient transduction. Notably, these preformed injectable scaffolds demonstrate hemocompatibility, cell viability and minimally inflammatory response as shown by ourin vitroandin vivostudies involving histology and immunophenotyping of infiltrating cells. This study marks the first instance of using preformed injectable scaffolds for delivery of lentivectors, which offers a non-invasive and localized approach for delivery of factors enablingin situlentiviral transduction suitable for both tissue engineering and immunotherapeutic applications.

Review: 3D cell models for organ-on-a-chip applications

Two-dimensional (2D) cultures do not fully reflect the human organs' physiology and the real effectiveness of the used therapy. Therefore, three-dimensional (3D) models are increasingly used in bioanalytical science. Organ-on-a-chip systems are used to obtain cellular in vitro models, better reflecting the human body's in vivo characteristics and allowing us to obtain more reliable results than standard preclinical models. Such 3D models can be used to understand the behavior of tissues/organs in response to selected biophysical and biochemical factors, pathological conditions (the mechanisms of their formation), drug screening, or inter-organ interactions. This review characterizes 3D models obtained in microfluidic systems. These include spheroids/aggregates, hydrogel cultures, multilayers, organoids, or cultures on biomaterials. Next, the methods of formation of different 3D cultures in Organ-on-a-chip systems are presented, and examples of such Organ-on-a-chip systems are discussed. Finally, current applications of 3D cell-on-a-chip systems and future perspectives are covered.

Impact of Viscosity on Human Hepatoma Spheroids in Soft Core-Shell Microcapsules

The extracellular environment regulates the structures and functions of cells, from the molecular to the tissue level. However, the underlying mechanisms influencing the organization and adaptation of cancer in three-dimensional (3D) environments are not yet fully understood. In this study, the influence of the viscosity of the environment is investigated on the mechanical adaptability of human hepatoma cell (HepG2) spheroids in vitro, using 3D microcapsule reactors formed with droplet-based microfluidics. To mimic the environment with different mechanical properties, HepG2 cells are encapsulated in alginate core-shell reservoirs (i.e., microcapsules) with different core viscosities tuned by incorporating carboxymethylcellulose. The significant changes in cell and spheroid distribution, proliferation, and cytoskeleton are observed and quantified. Importantly, changes in the expression and distribution of F-actin and keratin 8 indicate the relation between spheroid stiffness and viscosity of the surrounding medium. The increase of F-actin levels in the viscous medium can indicate an enhanced ability of tumor cells to traverse dense tissue. These results demonstrate the ability of cancer cells to dynamically adapt to the changes in extracellular viscosity, which is an important physical cue regulating tumor development, and thus of relevance in cancer biology.

3D printed bio-ceramic loaded PEGDA/vitreous carbon composite: Fabrication, characterization, and life cycle assessment

Stereolithography (SLA) is gaining vast popularity in the development of three-dimensional parts with customized materials for tissue engineering applications. Consequently, developing customized materials like bio-composites (bio-polymers and bio-ceramics) is the basic pillar that meets the application requirement. Photo-crosslinkable poly(ethylene glycol) diacrylate (PEGDA) has outstanding biocompatibility and biophysical properties for tissue engineering. But, because of its poor mechanical properties, its scope is limited to load-bearing applications. This research aims to enhance the mechanical and tribological properties of PEGDA by reinforcing Vitreous Carbon (VC) bioceramic. Therefore, 1 to 5 wt % of VC have been added in PEGDA and developed novel PEGDA/VC composite resins for SLA. The rheological and sedimentation test have been performed to check the suitability for SLA printing. Afterward, printed materials have been characterized by fourier transform infrared spectrometer, X-ray diffraction, thermogravimetric analysis, optical profilometer, and scanning electron microscope. Moreover, tensile compression, flexural, and tribological properties have been evaluated. It was found that the addition of VC in PEGDA enhanced its mechanical, thermal, and tribological properties. Besides, a life cycle assessment of materials and energy resources in SLA process has been performed to investigate the environmental impact.

Recent Methods for Modifying Mechanical Properties of Tissue-Engineered Scaffolds for Clinical Applications

The limited regenerative capacity of the human body, in conjunction with a shortage of healthy autologous tissue, has created an urgent need for alternative grafting materials. A potential solution is a tissue-engineered graft, a construct which supports and integrates with host tissue. One of the key challenges in fabricating a tissue-engineered graft is achieving mechanical compatibility with the graft site; a disparity in these properties can shape the behaviour of the surrounding native tissue, contributing to the likelihood of graft failure. The purpose of this review is to examine the means by which researchers have altered the mechanical properties of tissue-engineered constructs via hybrid material usage, multi-layer scaffold designs, and surface modifications. A subset of these studies which has investigated the function of their constructs in vivo is also presented, followed by an examination of various tissue-engineered designs which have been clinically translated.

Assessment of 3D-Printed Polycaprolactone, Hydroxyapatite Nanoparticles and Diacrylate Poly(ethylene glycol) Scaffolds for Bone Regeneration

Notwithstanding the advances achieved in the last decades in the field of synthetic bone substitutes, the development of biodegradable 3D-printed scaffolds with ideal mechanical and biological properties remains an unattained challenge. In the present work, a new approach to produce synthetic bone grafts that mimic complex bone structure is explored. For the first time, three scaffolds of various composition, namely polycaprolactone (PCL), PCL/hydroxyapatite nanoparticles (HANp) and PCL/HANp/diacrylate poly(ethylene glycol) (PEGDA), were manufactured by extrusion. Following the production and characterisation of the scaffolds, an in vitro evaluation was carried out using human dental pulp stem/stromal cells (hDPSCs). Through the findings, it was possible to conclude that, in all groups, the scaffolds were successfully produced presenting networks of interconnected channels, adequate porosity for migration and proliferation of osteoblasts (approximately 50%). Furthermore, according to the in vitro analysis, all groups were considered non-cytotoxic in contact with the cells. Nevertheless, the group with PEGDA revealed hydrophilic properties (15.15° ± 4.06) and adequate mechanical performance (10.41 MPa ± 0.934) and demonstrated significantly higher cell viability than the other groups analysed. The scaffolds with PEGDA suggested an increase in cell adhesion and proliferation, thus are more appropriate for bone regeneration. To conclude, findings in this study demonstrated that PCL, HANp and PEGDA scaffolds may have promising effects on bone regeneration and might open new insights for 3D tissue substitutes.

Edible Pleurotus eryngii Papery Food Prepared by Papermaking Process

The objective of the current study was to evaluate the feasibility of papery food with Pleurotus eryngii (P. eryngii) as a raw material using the papermaking process. The physical, chemical, structural, and thermal degradation properties were studied as well as the sensory evaluation of the papery food from P. eryngii mycelia (PMP), stems (PSP), caps (PCP), and whole fruiting bodies (PEP). The results indicated that the colors from PSP, PCP, and PEP were clearly different from PMP. Thicker PSP and PMP had a smoother surface and better crispness compared to PCP. Moreover, PSP had better moisture resistance and thermal decomposition performance compared to the other groups. Nutritional composition and Fourier-transform infrared spectroscopy suggested abundant polysaccharide and protein content in all of the papery food. Finally, sensory evaluation showed that the formability, mouth feel, and overall palatability of PSP and PMP were more popular among consumers. Overall, this study provides a novel method for the preparation of papery food and provides a potential new mechanism for the further development and utilization of the fruiting bodies and mycelium of P. eryngii.

Aggressive strategies for regenerating intervertebral discs: stimulus-responsive composite hydrogels from single to multiscale delivery systems

As our research on the physiopathology of intervertebral disc degeneration (IVD degeneration, IVDD) has advanced and tissue engineering has rapidly evolved, cell-, biomolecule- and nucleic acid-based hydrogel grafting strategies have been widely investigated for their ability to overcome the harsh microenvironment of IVDD. However, such single delivery systems suffer from excessive external dimensions, difficult performance control, the need for surgical implantation, and difficulty in eliminating degradation products. Stimulus-responsive composite hydrogels have good biocompatibility and controllable mechanical properties and can undergo solution-gel phase transition under certain conditions. Their combination with ready-to-use particles to form a multiscale delivery system may be a breakthrough for regenerative IVD strategies. In this paper, we focus on summarizing the progress of research on the stimulus response mechanisms of regenerative IVD-related biomaterials and their design as macro-, micro- and nanoparticles. Finally, we discuss multi-scale delivery systems as bioinks for bio-3D printing technology for customizing personalized artificial IVDs, which promises to take IVD regenerative strategies to new heights.

Incorporation of Mycobacteriophage Fulbright into Polycaprolactone Electrospun Nanofiber Wound Dressing

The Genus Mycobacterium includes pathogens known to cause disease in mammals such as tuberculosis (Mycobacterium tuberculosis) and skin infections (M. abscessus). M. smegmatis is a model bacterium that can cause opportunistic infections in human tissues and, rarely, a respiratory disease. Due to the emergence of multidrug-resistant bacteria, phage therapy is potentially an alternative way of treating these bacterial infections. As bacteriophages are specific to their bacterial host, it ensures that the normal flora is unharmed. Fulbright is a mycobacteriophage that infects the host bacteria M. smegmatis. The main goal of this study is to incorporate Mycobacteriophage Fulbright into a polycaprolactone (PCL) nanofiber and test its antimicrobial effect against the host bacteria, M. smegmatis. Stability tests conducted over 7 days showed that the phage titer does not decrease when in contact with PCL, making it a promising vehicle for phage delivery. Antimicrobial assays showed that PCL_Fulbright effectively reduces bacterial concentration after 24 h of contact. In addition, when stored at -20 °C, the phage remains viable for up to eleven months in the fiber. Fulbright addition on the nanofibrous mats resulted in an increase in water uptake and decrease in the mechanical properties (strength and Young's modulus) of the membranes, indicating that the presence of phage Fulbright can greatly enhance the physical and mechanical properties of the PCL. Cytotoxicity assays showed that PCL_Fulbright is not cytotoxic to Balbc/3T3 mouse embryo fibroblast cell lines; thus, phage-incorporated PCL is a promising alternative to antibiotics in treating skin infections.

Biocompatible chitosan/polyethylene glycol/multi-walled carbon nanotube composite scaffolds for neural tissue engineering

Carbon nanotube (CNT) composite materials are very attractive for use in neural tissue engineering and biosensor coatings. CNT scaffolds are excellent mimics of extracellular matrix due to their hydrophilicity, viscosity, and biocompatibility. CNTs can also impart conductivity to other insulating materials, improve mechanical stability, guide neuronal cell behavior, and trigger axon regeneration. The performance of chitosan (CS)/polyethylene glycol (PEG) composite scaffolds could be optimized by introducing multi-walled CNTs (MWCNTs). CS/PEG/CNT composite scaffolds with CNT content of 1%, 3%, and 5% (1%=0.01 g/mL) were prepared by freeze-drying. Their physical and chemical properties and biocompatibility were evaluated. Scanning electron microscopy (SEM) showed that the composite scaffolds had a highly connected porous structure. Transmission electron microscope (TEM) and Raman spectroscopy proved that the CNTs were well dispersed in the CS/PEG matrix and combined with the CS/PEG nanofiber bundles. MWCNTs enhanced the elastic modulus of the scaffold. The porosity of the scaffolds ranged from 83% to 96%. They reached a stable water swelling state within 24 h, and swelling decreased with increasing MWCNT concentration. The electrical conductivity and cell adhesion rate of the scaffolds increased with increasing MWCNT content. Immunofluorescence showed that rat pheochromocytoma (PC12) cells grown in the scaffolds had characteristics similar to nerve cells. We measured changes in the expression of nerve cell markers by quantitative real-time polymerase chain reaction (qRT-PCR), and found that PC12 cells cultured in the scaffolds expressed growth-associated protein 43 (GAP43), nerve growth factor receptor (NGFR), and class III β‍-tubulin (TUBB3) proteins. Preliminary research showed that the prepared CS/PEG/CNT scaffold has good biocompatibility and can be further applied to neural tissue engineering research.

Evaluation of Polycaprolactone Electrospun Nanofiber-Composites for Artificial Skin Based on Dermal Fibroblast Culture

The study’s aim was to develop a dermal equivalent scaffold that can mimic the architecture and biological performance of the human dermis. Poly ε-caprolactone (PCL) electrospun nanofiber material (ENF) was assembled with polyethylene glycol diacrylate (PEGDA), sodium alginate (SA) and type I collagen (CG1) to develop three groups of dermal equivalent scaffolds. These scaffolds were named PEGDA-PCL, SA-PCL and CG1-PCL. Scanning electron microscopy (SEM) images of cell-free scaffolds’ top and cross-sectional surface were collected and analyzed to examine internal morphology, specifically the adhesiveness of PCL fibers with the different scaffolds. Human dermal fibroblasts were cultured on each of the scaffolds. Cell viability studies including cell adhesion, cell differentiation and stress fiber production were conducted on each scaffold. Furthermore, the architectural integrity of each scaffold was verified by degradation analysis for 2 weeks by soaking each scaffold in phosphate-buffered saline (PBS) solution. Finally, we conducted rheological characteristics of each scaffold. Based on our results from the above analysis, the study concluded that CG1-PCL is best suitable for the dermal equivalent model and has potential to be used as a graft for skin repair.

Facile Preparation of Tunicate-Inspired Chitosan Hydrogel Adhesive with Self-Healing and Antibacterial Properties

In order to replace traditional wound treatments such as sutures, tissue adhesives with strong wet tissue adhesion and biocompatibility have attracted more attention to the applications of non-invasive wound closure. Herein, inspired by tunicate adhesive protein, a series of 2,3,4-trihydroxybenzaldehyde (TBA)-modified chitosan hydrogels (CS-TBA-Fe) were prepared by easily mixing the solutions of chitosan-FeCl₃ and TBA via the Schiff-base reaction and the coordination between Fe³⁺ and pyrogallol groups. The gelation time was greatly shortened to only several seconds after induced even trace Fe³⁺. The hydrogel (CS-TBA-Fe) exhibited ~12-fold enhanced wet tissue adhesion strength (60.3 kPa) over the commercial fibrin glue. Meanwhile, the hydrogel also showed robust adhesion to various substrates such as wood, PMMA, and aluminum. The swelling ratio and rheological property can be simply controlled by changing the concentrations of chitosan, TBA, and Fe³⁺. Moreover, the hydrogel displayed a rapid and highly efficient self-healing ability and an excellent antibacterial activity against E. coli. The overall results show that the CS-TBA-Fe hydrogel with enhanced wet adhesiveness will be a promising tissue adhesive material.

Composites Composed of Hydrophilic and Hydrophobic Polymers, and Hydroxyapatite Nanoparticles: Synthesis, Characterization, and Study of Their Biocompatible Properties

The creation of artificial biocomposites consisting of biocompatible materials in combination with bioactive molecules is one of the main tasks of tissue engineering. The development of new materials, which are biocompatible, functional, and also biodegradable in vivo, is a specific problem. Two types of products can be formed from these materials in the processes of biodegradation. The first types of substances are natural for a living organism and are included in the metabolism of cells, for example, sugars, lactic, glycolic, and β-hydroxybutyric acids. Substances that are not metabolized by cells represent the other type. In the latter case, such products should not be toxic, and their concentration when entering the bloodstream should not exceed the established maximum permissible level. The composite materials based on a mixture of biodegradable synthetic and natural polymers with the addition of hydroxyapatite nanoparticles, which acts as a stabilizer of the dispersed system during production of the composite, and which is a biologically active component of the resulting matrix, were obtained and studied. The indirect effect of the shape, size, and surface charge of hydroxyapatite nanoparticles on the structure and porosity of the formed matrix was shown. An in vivo study showed the absence of acute toxicity of the developed composites.

In vitroandin vivoeffect of polycaprolactone nanofiber coating on polyethylene glycol diacrylate scaffolds for intervertebral disc repair

Polyethylene glycol diacrylate (PEGDA) is an important class of photosensitive polymer with many tissue engineering applications. This study compared PEGDA and polycaprolactone (PCL) nanofiber matrix (NFM) coated PEGDA, referred to as PCL-PEGDA, scaffolds for their application in multiple tissue repair such as articular cartilage, nucleus pulposus of the intervertebral disc (IVD). We examined each scaffold morphology, porosity, swelling ratio, degradation, mechanical strength, andin vitrocytocompatibility properties. A defect was created in Sprague Dawley rat tail IVD by scraping native cartilage tissue and disc space, then implanting the scaffolds in the disc space for 4 weeks to evaluatein vivoefficacy of multi-tissue repair. Maintenance of disc height and creation of a new cell matrix was assessed to evaluate each scaffold's ability to repair the tissue defect. Although both PEGDA and PCL-PEGDA scaffolds showed similar porosity ∼73%, we observed distinct topographical characteristics and a higher effect of degradation on the water-absorbing capacity for PEGDA compared to PCL-PEGDA. Mechanical tests showed higher compressive strength and modulus of PCL-PEGDA compared to PEGDA.In vitrocell studies show that the PCL NFM layer covering PEGDA improved osteoblast cell adhesion, proliferation, and migration into the PEGDA layer.In vivostudies concluded that the PEGDA scaffold alone was not ideal for implantation in rat caudal disc space without PCL nanofiber coating due to low compressive strength and modulus.In vivoresults confirm that the PCL-PEGDA scaffold-maintained disc space and created a proteoglycan and collagen-rich new tissue matrix in the defect site after 4 weeks of scaffold implantation. We concluded that our developed PCL-PEGDA has the potential to be used in multi-tissue defect site repair.

Fabrication of Biomedical Scaffolds Using Biodegradable Polymers

Degradable polymers are used widely in tissue engineering and regenerative medicine. Maturing capabilities in additive manufacturing coupled with advances in orthogonal chemical functionalization methodologies have enabled a rapid evolution of defect-specific form factors and strategies for designing and creating bioactive scaffolds. However, these defect-specific scaffolds, especially when utilizing degradable polymers as the base material, present processing challenges that are distinct and unique from other classes of materials. The goal of this review is to provide a guide for the fabrication of biodegradable polymer-based scaffolds that includes the complete pathway starting from selecting materials, choosing the correct fabrication method, and considering the requirements for tissue specific applications of the scaffold.

Use of dissolved hyperpolarized species in NMR: Practical considerations

Hyperpolarization techniques that can transiently boost nuclear spin polarization are generally carried out at low temperature - as in the case of dynamic nuclear polarization - or at high temperature in the gaseous state - as in the case of optically pumped noble gases. This review aims at describing the various issues and challenges that have been encountered during dissolution of hyperpolarized species, and solutions to these problems that have been or are currently proposed in the literature. During the transport of molecules from the polarizer to the NMR detection region, and when the hyperpolarized species or a precursor of hyperpolarization (e.g. parahydrogen) is introduced into the solution of interest, several obstacles need to be overcome to keep a high level of final magnetization. The choice of the magnetic field, the design of the dissolution setup, and ways to isolate hyperpolarized compounds from relaxation agents will be presented. Due to the non-equilibrium character of the hyperpolarization, new NMR pulse sequences that perform better than the classical ones will be described. Finally, three applications in the field of biology will be briefly mentioned.

Thiol-Ene Click Reaction Initiated Rapid Gelation of PEGDA/Silk Fibroin Hydrogels

In this work, poly(ethylene glycol) diacrylate (PEGDA) molecules were grafted to silk fibroin (SF) molecules via a thiol-ene click reaction under 405 nm UV illumination for the fabrication of a PEGDA/SF composite hydrogel. The composite hydrogels could be prepared in a short and controllable gelation time without the use of a photoinitiator. Features relevant to the drug delivery of the PEGDA/SF hydrogels were assessed, and the hydrogels were characterized by various techniques. The results showed that the prepared PEGDA/SF hydrogels demonstrated a good sustained-release performance with limited swelling behavior. It was found that a prior cooling step can improve the compressive strength of the hydrogels effectively. Additionally, the MTT assay indicated the prepared PEGDA/SF hydrogel is non-cytotoxic. Subcutaneous implantation of the PEGDA/SF hydrogel in Kunming mice did not induce an obvious inflammation, which revealed that the prepared PEGDA/SF hydrogel possessed good biocompatibility. Furthermore, the mechanism of the gelation process was discussed.