Mechanical performance of elastomeric PGS scaffolds under dynamic conditions

A 3D-Printed Cuttlefish Bone Elastomeric Sponge Rapidly Controlling Noncompressible Hemorrhage

Developing a self-expanding hemostatic sponge with high blood absorption and rapid shape recovery for noncompressible hemorrhage remains a challenge. In this study, a 3D-printed cuttlefish bone elastomeric sponge (CBES) is fabricated, which combined ordered channels and porous structures, presented tunable mechanical strength, and shape memory potentials. The incorporation of cuttlefish bone powder (CBp) plays key roles in concentrating blood components, promoting aggregation of red blood cells and platelets, and activating platelets, which makes CBES show enhanced hemostatic performance compared with commercial gelatin sponges in vivo. Moreover, CBES promotes more histiocytic infiltration and neovascularization in the early stage of degradation than gelatin sponges, which is conducive to the regeneration and repair of injured tissue. To conclude, CBp loaded 3D-printed elastomeric sponges can promote coagulation, present the potential to guide tissue healing, and broaden the hemostatic application of traditional Chinese medicine.

Layer-by-layer assembly of poly-l-lysine/hyaluronic acid protein reservoirs on poly(glycerol sebacate) surfaces

The modification of biomaterial surfaces has become increasingly relevant in the context of ongoing advancements in tissue engineering applications and the development of tissue-mimicking polymer materials. In this study, we investigated the layer-by-layer (LbL) deposition of polyelectrolyte multilayer protein reservoirs consisting of poly-l-lysine (PLL) and hyaluronic acid (HA) on the hydrophobic surface of poly(glycerol sebacate) (PGS) elastomer. Using the methods of isothermal titration calorimetry and surface plasmon resonance, we systematically investigated the interactions between the polyelectrolytes and evaluated the deposition process in real time, providing insight into the phenomena associated with film assembly. PLL/HA LbL films deposited on PGS showed an exceptional ability to incorporate bone morphogenetic protein-2 (BMP-2) compared to other growth factors tested, thus highlighting the potential of PLL/HA LbL films for osteoregenerative applications. The concentration of HA solution used for film assembly did not affect the thickness and topography of the (PLL/HA)10 films, but had a notable impact on the hydrophilicity of the PGS surface and the BMP-2 release kinetics. The release kinetics were successfully described using the Weibull model and hyperbolic tangent function, underscoring the potential of these less frequently used models to compare the protein release from LbL protein reservoirs.

Effect of static tensile stress on enzymatic degradation of poly(glycerol sebacate)

Poly(glycerol sebacate) (PGS) is an excellent scaffold material in tissue engineering due to good biocompatibility and tunable mechanical properties. The degradation properties of PGS have been primarily explored in static phosphate buffer solution or enzyme solution. It is vital to understand how the tensile stress affect the degradation rate. In this study, PGS was synthetized by melt polycondensation and its properties were characterized. Then an in vitro degradation device which could provide different constant tensile stresses was carefully designed and established, and the enzymatic degradation of PGS was tested under 0-150 kPa at 37°C. It was found that holes of PGS surface arranged almost parallel to each other and perpendicular to the direction of tensile stresses at 100 kPa and 150 kPa after 2-4 days degradation. After 8 days degradation, the ultimate tensile strength (UTS) of PGS at 150 kPa was 0.28 MPa and the elastic modulus was 1.11 MPa, while the UTS of PGS was 0.44 MPa and the elastic modulus was 1.63 MPa before degradation, both of them have significant differences. Hence, the tensile stress and degradation time were proportional to the appear time and size of holes, leading to the decrease of mass loss, UTS and elastic modulus. The relationship between stress and PGS degradation rates was quantitatively described through our degradation experiments, providing guidance for suitable PGS applications in the future.

Different methods of synthesizing poly(glycerol sebacate) (PGS): A review

Poly(glycerol sebacate) (PGS) is a biodegradable elastomer that has attracted increasing attention as a potential material for applications in biological tissue engineering. The conventional method of synthesis, first described in 2002, is based on the polycondensation of glycerol and sebacic acid, but it is a time-consuming and energy-intensive process. In recent years, new approaches for producing PGS, PGS blends, and PGS copolymers have been reported to not only reduce the time and energy required to obtain the final material but also to adjust the properties and processability of the PGS-based materials based on the desired applications. This review compiles more than 20 years of PGS synthesis reports, reported inconsistencies, and proposed alternatives to more rapidly produce PGS polymer structures or PGS derivatives with tailor-made properties. Synthesis conditions such as temperature, reaction time, reagent ratio, atmosphere, catalysts, microwave-assisted synthesis, and PGS modifications (urethane and acrylate groups, blends, and copolymers) were revisited to present and discuss the diverse alternatives to produce and adapt PGS.

Porous biomaterials for tissue engineering: a review

The field of biomaterials has grown rapidly over the past decades. Within this field, porous biomaterials have played a remarkable role in: (i) enabling the manufacture of complex three-dimensional structures; (ii) recreating mechanical properties close to those of the host tissues; (iii) facilitating interconnected structures for the transport of macromolecules and cells; and (iv) behaving as biocompatible inserts, tailored to either interact or not with the host body. This review outlines a brief history of the development of biomaterials, before discussing current materials proposed for use as porous biomaterials and exploring the state-of-the-art in their manufacture. The wide clinical applications of these materials are extensively discussed, drawing on specific examples of how the porous features of such biomaterials impact their behaviours, as well as the advantages and challenges faced, for each class of the materials.

Preparation and characterization of a new bio nanocomposites based poly(glycerol sebacic-urethane) containing nano-clay (Cloisite Na+ ) and its potential application for tissue engineering

Nanocomposites containing clay nanoparticles often present favorable properties such as good mechanical and thermal properties. They frequently have been studied for tissue engineering (TE) and regenerative medicine applications. On the other hand, poly(glycerol sebacate) (PGS), a revolutionary bioelastomer, has exhibited substantial potential as a promising candidate for biomedical application. Here, we present a facile approach to synthesizing stiff, elastomeric nanocomposites from sodium-montmorillonite nano-clay (MMT) in the commercial name of Cloisite Na⁺ and poly(glycerol sebacate urethane) (PGSU). The strong physical interaction between the intercalated Cloisite Na⁺ platelets and PGSU chains resulted in desirable property combinations for TE application to follow. The addition of 5% MMT nano-clay resulted in an over two-fold increase in the tensile modulus, increased the onset thermal decomposition temperature of PGSU matrix by 18°C, and noticeably improved storage modulus of the prepared scaffolds, compared with pure PGSU. As well, Cloisite Na⁺ enhanced the hydrophilicity and water uptake ability of the samples and accelerated the in-vitro biodegradation rate. Finally, in-vitro cell viability assay using L929 mouse fibroblast cells indicated that incorporating Cloisite Na⁺ nanoparticles into the PGSU network could improve the cell attachment and proliferation, rendering the synthesized bioelastomers potentially suitable for TE and regenerative medicine applications.

Strategies for constructing pluripotent stem cell- and progenitor cell-derived three-dimensional cardiac micro-tissues

Three-dimensional (3D) cardiac micro-tissue is a promising model for simulating the structural and functional features of heart in vitro. This scientific achievement provides a platform for exploration about the mechanisms on the development, damage, and regeneration of tissue, hence, paving a way toward development of novel therapies for heart diseases. However, 3D micro-tissue technology is still in its infant stages faced with many challenges such as incompleteness of the tissue microarchitecture, loss of the resident immune cells, poor reproducibility, and deficiencies in continuously feeding the nutrients and removing wastes during micro-tissue culturing. There is an urgent need to optimize the construction of 3D cardiac micro-tissue and improve functions of the involved cells. Therefore, scaffolds and cell resources for building 3D cardiac micro-tissues, strategies for inducing the maturation and functionalization of pluripotent stem cell- or cardiac progenitor cell-derived cardiomyocytes, and the major challenges were reviewed in this writing to enable future fabrication of 3D cardiac micro-tissues or organoids for drug screening, disease modeling, regeneration treatment, and so on.

Poly(Glycerol Sebacate) in Biomedical Applications-A Review of the Recent Literature

Poly(glycerol sebacate) (PGS) continues to attract attention for biomedical applications owing to its favorable combination of properties. Conventionally polymerized by a two-step polycondensation of glycerol and sebacic acid, variations of synthesis parameters, reactant concentrations or by specific chemical modifications, PGS materials can be obtained exhibiting a wide range of physicochemical, mechanical, and morphological properties for a variety of applications. PGS has been extensively used in tissue engineering (TE) of cardiovascular, nerve, cartilage, bone and corneal tissues. Applications of PGS based materials in drug delivery systems and wound healing are also well documented. Research and development in the field of PGS continue to progress, involving mainly the synthesis of modified structures using copolymers, hybrid, and composite materials. Moreover, the production of self-healing and electroactive materials has been introduced recently. After almost 20 years of research on PGS, previous publications have outlined its synthesis, modification, properties, and biomedical applications, however, a review paper covering the most recent developments in the field is lacking. The present review thus covers comprehensively literature of the last five years on PGS-based biomaterials and devices focusing on advanced modifications of PGS for applications in medicine and highlighting notable advances of PGS based systems in TE and drug delivery.

The Effect of Pore Size Distribution and l-Lysine Modified Apatite Whiskers (HAP) on Osteoblasts Response in PLLA/HAP Foam Scaffolds Obtained in the Thermally Induced Phase Separation Process

In this research, we prepared foam scaffolds based on poly(l-lactide) (PLLA) and apatite whiskers (HAP) using thermally induced phase separation technique supported by the salt leaching process (TIPS-SL). Using sodium chloride having a size of (a) 150-315 μm, (b) 315-400 μm, and (c) 500-600 μm, three types of foams with different pore sizes have been obtained. Internal structure of the obtained materials has been investigated using SEM as well as μCT. The materials have been studied by means of porosity, density, and compression tests. As the most promising, the composite prepared with salt size of 500-600 μm was prepared also with the l-lysine modified apatite. The osteoblast hFOB 1.19 cell response for the scaffolds was also investigated by means of cell viability, proliferation, adhesion/penetration, and biomineralization. Direct contact cytotoxicity assay showed the cytocompatibility of the scaffolds. All types of foam scaffolds containing HAP whiskers, regardless the pore size or l-lysine modification induced significant stimulatory effect on the cal-cium deposits formation in osteoblasts. The PLLA/HAP scaffolds modified with l-lysine stimulated hFOB 1.19 osteoblasts proliferation. Compared to the scaffolds with smaller pores (150-315 µm and 315-400 µm), the PLLA/HAP foams with large pores (500-600 µm) promoted more effective ad-hesion of osteoblasts to the surface of the biomaterial.

Low-Hysteresis and Ultrasensitive Microcellular Structures for Wearable Electronic Applications

Wearable technologies offer the opportunity to record human physiological signals in real time, in a noninvasive way, and the data can be used to aid in the early detection of abnormal health conditions. Here, we demonstrate how the interconnected porosity can be used to increase the sensitivity and linearity of capacitive pressure sensors. The finite element analysis supports the experimental observation that the movement of air during the dynamic mechanical loading is responsible for the high sensitivity observed (0.18 ± 0.01 kPa^-1) when compared with the solid poly(glycerol sebacate) sensor (0.0042 ± 0.0002 kPa^-1). The porous sensors present strain insensitivity and remarkable linearity over the entire range of applied mechanical pressure (0-6 kPa), capable of detecting both static and dynamic mechanical stimuli (17 nm/s), and a response time of 50 ms, without evidence of fatigue or electrical hysteresis over 10,000 mechanical cycles. The outstanding features of the porous sensors can find a broad range of applications in real-time health monitoring, from demanding movements like walking/running, to small deformations resulting from breathing or heart beating. The ultrasensitive microcellular structures synthesized in this study can be applied to other types of sensing transductions to obtain tunable and function-specific sensors with high sensitivity.

Environmentally Friendly and Biodegradable Ultrasensitive Piezoresistive Sensors for Wearable Electronics Applications

Highly sensitive, flexible sensors that can be manufactured with minimum environmental footprint and be seamlessly integrated into wearable devices are required for real-time tracking of complex human movement, gestures, and health conditions. This study reports on how biodegradation can be used to enhance the sensitivity and electromechanical performance of piezoresistive sensors. Poly(glycerol sebacate) (PGS) elastomeric porous sensor was synthesized and blended with multiwall carbon nanotubes (MWCNTs) and sodium chloride (NaCl). Because of their unique porous characteristics, a single linear behavior over a large range of pressures (≤8 kPa) and an increase in their sensitivity from 0.12 ± 0.03 kPa^-1 up to 8.00 ± 0.20 kPa^-1 was achieved after 8 weeks in a simulated body fluid media. They can detect very low pressures (100 Pa), with negligible hysteresis, reliability, long lifetime (>200 000 cycles), short response time (≤20 ms), and high force sensitivity (≤4 mN). The characteristics of the developed foam sensors match the sensing characteristics of the human finger to pave the way toward low-footprint wearable devices for applications including human movement and condition monitoring, recreation, health and wellness, virtual reality, and tissue engineering.