In vitro evaluation of doxorubicin release from diopside particles on MG-63 and HF spheroids as a 3D model of tumor and healthy tissues.

Local drug delivery systems based on bioceramics ensure safe and effective treatment of bone defects and anticancer therapy. A promising drug delivery scaffold material for bone treatment applications is diopside (CaMgSi2O6) which is bioactive, degradable, and possesses drug-release ability. Currently, in vitro assessment of drug release from biomaterials is performed mostly on a 2D cell monolayer. However, to interpret and integrate biochemical signals, cells need a 3D microenvironment that provides cell-cell and cell-extracellular matrix interactions. In this regard, 3D cell models are gaining popularity. In this work, we proposed the protocol for evaluation of the effect of doxorubicin released from diopside on MG-63 cells and primary human fibroblasts in 3D culture conditions. Tissue spheroids with similar diameters were incubated with doxorubicin-loaded diopside for 72 h, the amount of diopside was calculated in accordance with the required doxorubicin concentration. We demonstrated that doxorubicin is gradually released from diopside and exhibits an activity similar to that of the pure drug at the same total concentration. It is important to note that doxorubicin was more potent on MG-63 spheroids compared to HF spheroids, which confirmed the reliability of spheroids as 3D models of tumor and healthy tissues.

Biodegradable Local Chemotherapy Platform with Prolonged and Controlled Release of Doxorubicin for the Prevention of Local Tumor Recurrence.

Local recurrence after surgical and therapeutic treatment remains a significant clinical problem in oncology. Recurrence may be due to imperfections in existing therapies, particularly chemotherapy. To improve antitumor activity and prevent local cancer recurrence while keeping toxicity at acceptable levels, we have developed and demonstrated a biodegradable local chemotherapy platform that provides controlled and prolonged drug release. The platform consists of a polycaprolactone (PCL) substrate, which provides the structural integrity of the platform and the predominant unidirectional drug release, and a thin multilayer coating (∼200 nm) containing doxorubicin (DOX). The coating is an electrostatic complex obtained by the layer-by-layer (LbL) assembly and consists of natural polyelectrolytes [poly-γ-glutamic acid (γ-PGA) and chitosan (CS) or poly-l-lysine (PLL)]. To improve the release stability, an ionic conjugate of DOX and γ-PGA was prepared and incorporated into the multilayer coating. By varying the structure of the coating by adding empty (without DOX) bilayers, we were able to control the kinetics of drug release. The resulting platforms contained equal numbers of empty bilayers and DOX-loaded bilayers (15 + 15 or 30 + 30 bilayers) with a maximum loading of 566 ng/cm2. The platforms demonstrated prolonged and fairly uniform drug release for more than 5 months while retaining antitumor activity in vitro on ovarian cancer cells (SKOV-3). The empty platforms (without DOX) showed good cytocompatibility and no cytotoxicity to human fibroblasts and SKOV-3 cells. This study presents the development of a local chemotherapy platform consisting of a PCL-based substrate which provides structural stability and a biodegradable polyelectrolyte layered coating which combines layers containing a polyanion ionic complex with DOX with empty bilayers to ensure prolonged and controlled drug release. Our results may provide a basis for improving the efficacy of chemotherapy using drug delivery systems.

Hybrid Implants Based on Calcium-Magnesium Silicate Ceramic Diopside as a Carrier of Recombinant BMP-2 and Demineralized Bone Matrix as a Scaffold: Ectopic Osteogenesis in Intramuscular Implantation in Mice.

High efficiency of hybrid implants based on calcium-magnesium silicate ceramic, diopside, as a carrier of recombinant BMP-2 and xenogenic demineralized bone matrix (DBM) as a scaffold for bone tissue regeneration was demonstrated previously using the model of critical size cranial defects in mice. In order to investigate the possibility of using these implants for growing autologous bone tissue using in vivo bioreactor principle in the patient's own body, effectiveness of ectopic osteogenesis induced by them in intramuscular implantation in mice was studied. At the dose of 7 µg of BMP-2 per implant, dense agglomeration of cells, probably skeletal muscle satellite precursor cells, was observed one week after implantation with areas of intense chondrogenesis, initial stage of indirect osteogenesis, around the implants. After 12 weeks, a dense bone capsule of trabecular structure was formed covered with periosteum and mature bone marrow located in the spaces between the trabeculae. The capsule volume was about 8-10 times the volume of the original implant. There were practically no signs of inflammation and foreign body reaction. Microcomputed tomography data showed significant increase of the relative bone volume, number of trabeculae, and bone tissue density in the group of mice with BMP-2-containing implant in comparison with the group without BMP-2. Considering that DBM can be obtained in practically unlimited quantities with required size and shape, and that BMP-2 is obtained by synthesis in E. coli cells and is relatively inexpensive, further development of the in vivo bioreactor model based on the hybrid implants constructed from BMP-2, diopside, and xenogenic DBM seems promising.

Commercial articulated collaborative in situ 3D bioprinter for skin wound healing.

In situ bioprinting is one of the most clinically relevant techniques in the emerging bioprinting technology because it could be performed directly on the human body in the operating room and it does not require bioreactors for post-printing tissue maturation. However, commercial in situ bioprinters are still not available on the market. In this study, we demonstrated the benefit of the originally developed first commercial articulated collaborative in situ bioprinter for the treatment of full-thickness wounds in rat and porcine models. We used an articulated and collaborative robotic arm from company KUKA and developed original printhead and correspondence software enabling in situ bioprinting on curve and moving surfaces. The results of in vitro and in vivo experiments show that in situ bioprinting of bioink induces a strong hydrogel adhesion and enables printing on curved surfaces of wet tissues with a high level of fidelity. The in situ bioprinter was convenient to use in the operating room. Additional in vitro experiments (in vitro collagen contraction assay and in vitro 3D angiogenesis assay) and histological analyses demonstrated that in situ bioprinting improves the quality of wound healing in rat and porcine skin wounds. The absence of interference with the normal process of wound healing and even certain improvement in the dynamics of this process strongly suggests that in situ bioprinting could be used as a novel therapeutic modality in wound healing.

Hydrogel-Inducing Graphene-Oxide-Derived Core-Shell Fiber Composite for Antibacterial Wound Dressing.

The study reveals the polymer-crosslinker interactions and functionality of hydrophilic nanofibers for antibacterial wound coatings. Coaxial electrospinning leverages a drug encapsulation protocol for a core-shell fiber composite with a core derived from polyvinyl alcohol and polyethylene glycol with amorphous silica (PVA-PEG-SiO2), and a shell originating from polyvinyl alcohol and graphene oxide (PVA-GO). Crosslinking with GO and SiO2 initiates the hydrogel transition for the fiber composite upon contact with moisture, which aims to optimize the drug release. The effect of hydrogel-inducing additives on the drug kinetics is evaluated in the case of chlorhexidine digluconate (CHX) encapsulation in the core of core-shell fiber composite PVA-PEG-SiO2-1x-CHX@PVA-GO. The release rate is assessed with the zero, first-order, Higuchi, and Korsmeyer-Peppas kinetic models, where the inclusion of crosslinking silica provides a longer degradation and release rate. CHX medicated core-shell composite provides sustainable antibacterial activity against Staphylococcus aureus.

Design, Fabrication, and Application of Mini-Scaffolds for Cell Components in Tissue Engineering.

The concept of "lockyballs" or interlockable mini-scaffolds fabricated by two-photon polymerization from biodegradable polymers for the encagement of tissue spheroids and their delivery into the desired location in the human body has been recently introduced. In order to improve control of delivery, positioning, and assembly of mini-scaffolds with tissue spheroids inside, they must be functionalized. This review describes the design, fabrication, and functionalization of mini-scaffolds as well as perspectives on their application in tissue engineering for precisely controlled cell and mini-tissue delivery and patterning. The development of functionalized mini-scaffolds advances the original concept of "lockyballs" and opens exciting new prospectives for mini-scaffolds' applications in tissue engineering and regenerative medicine and their eventual clinical translation.

Auxetic Metamaterials for Biomedical Devices: Current Situation, Main Challenges, and Research Trends.

Auxetic metamaterials are characterized by a negative Poisson ratio (NPR) and display an unexpected property of lateral expansion when stretched and densification when compressed. Auxetic properties can be achieved by designing special microstructures, hence their classification as metamaterials, and can be manufactured with varied raw materials and methods. Since work in this field began, auxetics have been considered for different biomedical applications, as some biological tissues have auxetic-like behaviour due to their lightweight structure and morphing properties, which makes auxetics ideal for interacting with the human body. This research study is developed with the aim of presenting an updated overview of auxetic metamaterials for biomedical devices. It stands out for providing a comprehensive view of medical applications for auxetics, including a focus on prosthetics, orthotics, ergonomic appliances, performance enhancement devices, in vitro medical devices for interacting with cells, and advanced medicinal clinical products, especially tissue engineering scaffolds with living cells. Innovative design and simulation approaches for the engineering of auxetic-based products are covered, and the relevant manufacturing technologies for prototyping and producing auxetics are analysed, taking into consideration those capable of processing biomaterials and enabling multi-scale and multi-material auxetics. An engineering design rational for auxetics-based medical devices is presented with integrative purposes. Finally, key research, development and expected technological breakthroughs are discussed.

Ultra-High Molecular Weight Polyethylene/Titanium-Hybrid Implant for Bone-Defect Replacement.

A hybrid implant with a structure mimicking that of natural bone was developed. Titanium alloy Ti-6Al-4V prepared with three-dimensional (3D)-printing technology was used to simulate the cortical-bone layer. The mismatch in the mechanical properties of bone and titanium alloy was solved by creating special perforations in the titanium's surface. Porous ultra-high molecular weight polyethylene (UHMWPE) with high osteogenous properties was used to simulate the cancellous-bone tissue. A method for creating a porous UHMWPE structure inside the titanium reinforcement is proposed. The porous UHMWPE was studied with scanning electron microscope (SEM) to confirm that the pores that formed were open, interconnected, and between 50 and 850 µm in size. Mechanical-compression tests done on the obtained UHMWPE/titanium-hybrid-implant samples showed that their mechanical properties simulated those of natural bone.

Porous Open-Сell UHMWPE: Experimental Study of Structure and Mechanical Properties.

Ultra-high molecular weight polyethylene (UHMWPE) is a bioinert polymer that is widely used as bulk material in reconstructive surgery for structural replacements of bone and cartilage. Porous UHMWPE can be used for trabecular bone tissue replacement, and it can be used in living cell studies as bioinert 3D substrate permeable to physiological fluids. It is important to develop techniques to govern the morphology of open-cell porous UHMWPE structures (pore size, shape, and connectivity), since this allows control over proliferation and differentiation in living cell populations. We report experimental results on the mechanical behavior of porous open-cell UHMWPE obtained through sacrificial removal (desalination) of hot-molded UHMWPE-NaCl powder mixtures with pore sizes in the range 75 µm to 500 µm. The structures were characterized using SEM and mechanically tested under static compression and dynamic mechanical analysis (DMA), bending, and tensile tests. Apparent elastic modulus and complex modulus were in the range of 1.2 to 2.5 MPa showing a weak dependence on cell size. Densification under compression caused the apparent elastic modulus to increase to 130 MPa.

Probing the complex thermo-mechanical properties of a 3D-printed polylactide-hydroxyapatite composite using in situ synchrotron X-ray scattering.

Polylactide (PLA)-hydroxyapatite (HAp) composite components have attracted extensive attentions for a variety of biomedical applications. This study seeks to explore how the biocompatible PLA matrix and the bioactive HAp fillers respond to thermo-mechanical environment of a PLA-HAp composite manufactured by 3D printing using Fused Filament Fabrication (FFF). The insight is obtained by in situ synchrotron small- and wide- angle X-ray scattering (SAXS/WAXS) techniques. The thermo-mechanical cyclic loading tests (0-20 MPa, 22-56 °C) revealed strain softening (Mullins effect) of PLA-HAp composite at both room and elevated temperatures (<56 °C), which can be attributed primarily to the non-linear deformation of PLA nanometre-scale lamellar structure. In contrast, the strain softening of the PLA amorphous matrix appeared only at elevated temperatures (>50 °C) due to the increased chain mobility. Above this temperature the deformation behaviour of the soft PLA lamella changes drastically. The thermal test (0-110 °C) identified multiple crystallisation mechanisms of the PLA amorphous matrix, including reversible stress-induced large crystal formation at room temperature, reversible coupled stress-temperature-induced PLA crystal formation appearing at around 60 °C, as well as irreversible heating-induced crystallisation above 92 °C. The shape memory test (0-3.75 MPa, 0-70 °C) of the PLA-HAp composite demonstrates a fixing ratio (strain upon unloading/strain before unloading) of 65% and rather a ∼100% recovery ratio, showing an improved shape memory property. These findings provide a new framework for systematic characterisation of the thermo-mechanical response of composites, and open up ways towards improved material design and enhanced functionality for biomedical applications.

Bulk Oriented UHMWPE/FMWCNT Films for Tribological Applications.

Bulk oriented films based on ultrahigh molecular weight polyethylene (UHMWPE) with a drawing ratio of 35 were prepared by using a low solvent concentration. Bulk oriented films were filled with fluorinated multi-walled carbon nanotubes (FMWCNTs). The structure of bulk oriented films on UHMWPE, which were manufactured at different stages of orientation, was investigated by scanning electron microscope (SEM) and differential scanning calorimetry (DSC). The addition of FMWCNTs at a concentration of 0.05 wt % in bulk oriented UHMWPE films led to an increase in the tensile strength by 10% (up to 1020 ± 23 MPa) compared to unfilled oriented films. However, the addition of FMWCNTs at a concentration of more than 0.5 wt % led to a decrease in tensile strength due to excessive accumulation of nanotubes and hindering of self-diffusion of UHMWPE macromolecules. The multiple increase in tensile strength, doubling the hardness, the formation of fibrillar structure, and the presence of carbon nanotubes led to a significant increase in tribological properties in bulk oriented films. Bulk oriented UHMWPE/1% FMWCNT films can be operated at a maximum contact pressure that is 18 times higher and exhibit a specific wear rate more than an order of magnitude and less than the traditional UHMWPE of isotropic structure. Bulk oriented UHMWPE/1% FMWCNT films have an extremely low dry coefficient of friction (COF) of 0.075 at a contact pressure of 31 MPa. The developed bulk oriented films can be used for manufacturing frictional surfaces for sliding bearings, or for acetabular cups for knee and hip endoprostheses.