Degradation behaviour of porous poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) scaffolds in cell culture.

Exploring the degradation behaviour of biomaterials in a complex in vitro physiological environment can assist in predicting their performance in vivo, yet this aspect remains largely unexplored. In this study, the in vitro degradation over 12 weeks of porous poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) bone scaffolds in human osteoblast (hOB) culture was investigated. The objective was to evaluate how the presence of cells influenced both the degradation behaviour and mechanical stability of these scaffolds. The molecular weight (Mw) of the scaffolds decreased with increasing incubation time and the Mw reduction rate (6.2 ± 0.4 kg mol-1 week-1) was similar to that observed when incubated in phosphate buffered saline (PBS) solution, implying that the scaffolds underwent hydrolytic degradation in hOB culture. The mass of the scaffolds increased by 0.8 ± 0.2 % in the first 4 weeks, attributed to cells attachment and extracellular matrix (ECM) deposition including biomineralisation. During the first 8 weeks, the nominal compressive modulus, E⁎, of the scaffolds remained constant. However, it increased significantly from Week 8 to 12, with increments of 55 % and 42 % in normal and lateral directions, respectively, attributed to the reinforcement effect of cells, ECM and minerals attached on the surface of the scaffold. This study has highlighted, that while the use of PBS in degradation studies is suitable for evaluating Mw changes it cannot predict changes in mechanical properties to PHBV scaffolds in the presence of cells and culture media. Furthermore, the PHBV scaffolds had mechanical stability in cell culture for 12 weeks validating their suitability for tissue engineering applications.

Targeting Agents in Biomaterial-Mediated Bone Regeneration.

Bone diseases are a global public concern that affect millions of people. Even though current treatments present high efficacy, they also show several side effects. In this sense, the development of biocompatible nanoparticles and macroscopic scaffolds has been shown to improve bone regeneration while diminishing side effects. In this review, we present a new trend in these materials, reporting several examples of materials that specifically recognize several agents of the bone microenvironment. Briefly, we provide a subtle introduction to the bone microenvironment. Then, the different targeting agents are exposed. Afterward, several examples of nanoparticles and scaffolds modified with these agents are shown. Finally, we provide some future perspectives and conclusions. Overall, this topic presents high potential to create promising translational strategies for the treatment of bone-related diseases. We expect this review to provide a comprehensive description of the incipient state-of-the-art of bone-targeting agents in bone regeneration.

Emerging Technologies of Three-Dimensional Printing and Mobile Health in COVID-19 Immunity and Regenerative Dentistry.

The ongoing coronavirus disease 2019 (COVID-19) pandemic highlights the importance of developing point-of-care (POC) antibody tests for monitoring the COVID-19 immune response upon viral infection or following vaccination, which requires three key aspects to achieve optimal monitoring, including three-dimensional (3D)-printed POC devices, mobile health (mHealth), and noninvasive sampling. As a critical tissue engineering concept, additive manufacturing (AM, also known as 3D printing) enables accurate control over the dimensional and architectural features of the devices. mHealth refers to the use of portable digital devices, such as smartphones, tablet computers, and fitness and medical wearables, to support health, which facilitates contact tracing, and telehealth consultations during the pandemic. Compared with invasive biosample (blood), saliva is of great importance in the spread and surveillance of COVID-19 as a noninvasive diagnostic method for virus detection and immune status monitoring. However, investigations into 3D-printed POC antibody test and mHealth using noninvasive saliva are relatively limited. Further exploration of 3D-printed antibody POC tests and mHealth applications to monitor antibody production for either disease onset or immune response following vaccination is warranted. This review briefly describes the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus and immune response after infection and vaccination, then discusses current widely used binding antibody tests using blood samples and enzyme-linked immunosorbent assays on two-dimensional microplates before focusing upon emerging POC technological platforms, such as field-effect transistor biosensors, lateral flow assay, microfluidics, and AM for fabricating immunoassays, and the possibility of their combination with mHealth. This review proposes that noninvasive biofluid sampling combined with 3D POC antibody tests and mHealth technologies is a promising and novel approach for POC detection and surveillance of SARS-CoV-2 immune response. Furthermore, as key concepts in dentistry, the application of 3D printing and mHealth was also included to facilitate the appreciation of cutting edge techniques in regenerative dentistry. This review highlights the potential of 3D printing and mHealth in both COVID-19 immunity monitoring and regenerative dentistry.

A Comparative Study of Mesoporous Silica and Mesoporous Bioactive Glass Nanoparticles as Non-Viral MicroRNA Vectors for Osteogenesis.

Micro-ribonucleic acid (miRNA)-based therapies show advantages for bone regeneration but need efficient intracellular delivery methods. Inorganic nanoparticles such as mesoporous bioactive glass nanoparticles (MBGN) and mesoporous silica nanoparticles (MSN) have received growing interest in the intracellular delivery of nucleic acids. This study explores the capacity of MBGN and MSN for delivering miRNA to bone marrow mesenchymal stem cells (BMSC) for bone regenerative purposes, with a focus on comparing the two in terms of cell viability, transfection efficiency, and osteogenic actions. Spherical MBGN and MSN with a particle size of ~200 nm and small-sized mesopores were prepared using the sol-gel method, and then the surface was modified with polyethyleneimine for miRNA loading and delivery. The results showed miRNA can be loaded into both nanoparticles within 2 h and was released sustainedly for up to 3 days. Confocal laser scanning microscopy and flow cytometry analysis indicated a high transfection efficiency (>64%) of both nanoparticles without statistical difference. Compared with MSN, MBGN showed stronger activation of alkaline phosphatase and activation of osteocalcin genes. This translated to a greater osteogenic effect of MBGN on BMSC, with Alizarin red staining showing greater mineralization compared with the MSN group. These findings show the potential for MBGN to be used in bone tissue engineering.

Salivary SARS-CoV-2 antibody detection using S1-RBD protein-immobilized 3D melt electrowritten poly(ε-caprolactone) scaffolds.

Sensitive detection of immunoglobulin antibodies against SARS-CoV-2 during the COVID-19 pandemic is critical to monitor the adaptive immune response after BNT162b2 mRNA vaccination. Currently employed binding antibody detection tests using 2D microplate-based enzyme-linked immunosorbent assays (ELISA) are limited by the degree of sensitivity. In this study, a 3D antibody test was developed by immobilizing the receptor-binding domain on Spike subunit 1 (S1-RBD) of SARS-CoV-2 onto engineered melt electrowritten (MEW) poly(ε-caprolactone) (PCL) scaffolds (pore: 500 µm, fiber diameter: 17 µm) using carbodiimide crosslinker chemistry. Protein immobilization was confirmed using X-ray photoelectron spectroscopy (XPS) by the presence of peaks corresponding with nitrogen. Self-developed indirect ELISA was performed to assess the functionality of the 3D platform in comparison with a standard 2D tissue culture plate (TCP) system, using whole unstimulated saliva samples from 14 non-vaccinated and 20 vaccinated participants (1- and 3- weeks post-dose 1; 3 days, 1 week and 3 weeks post-dose 2) without prior SARS-CoV-2 infection. The three-dimensional S1-RBD PCL scaffolds, while demonstrating a kinetic trend comparable to 2D TCP, exhibited significantly higher sensitivity and detection levels for all three immunoglobulins assayed (IgG, IgM, and IgA). These novel findings highlight the potential of MEW PCL constructs in the development of improved low-cost, point-of-care, and self-assessing diagnostic platforms for the detection and monitoring of SARS-CoV-2 antibodies.

In vitro evaluation of porous poly(hydroxybutyrate-co-hydroxyvalerate)/akermanite composite scaffolds manufactured using selective laser sintering.

Incorporation of a bioactive mineral filler in a biodegradable polyester scaffold is a promising strategy for scaffold assisted bone tissue engineering (TE). The current study evaluates the in vitro behavior of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)/Akermanite (AKM) composite scaffolds manufactured using selective laser sintering (SLS). Exposure of the mineral filler on the surface of the scaffold skeleton was evident from in vitro mineralization in PBS. PHBV scaffolds and solvent cast films served as control samples and all materials showed preferential adsorption of fibronectin compared to serum albumin as well as non-cytotoxic response in human osteoblasts (hOB) at 24 h. hOB culture for up to 21 days revealed that the metabolic activity in PHBV films and scaffolds was significantly higher than that of PHBV/AKM scaffolds within the first two weeks of incubation. Afterwards, the metabolic activity in PHBV/AKM scaffolds exceeded that of the control samples. Confocal imaging showed cell penetration into the porous scaffolds. Significantly higher ALP activity was observed in PHBV/AKM scaffolds at all time points in both basal and osteogenic media. Mineralization during cell culture was observed on all samples with PHBV/AKM scaffolds exhibiting distinctly different mineral morphology. This study has demonstrated that the bioactivity of PHBV SLS scaffolds can be enhanced by incorporating AKM, making this an attractive candidate for bone TE application.

Surface Modification of Pure Zinc by Acid Etching: Accelerating the Corrosion Rate and Enhancing Biocompatibility and Antibacterial Characteristics.

Zinc (Zn) has recently been identified as an auspicious biodegradable metal for medical implants and devices due to its tunable mechanical properties and good biocompatibility. However, the slow corrosion rate of Zn in a physiological environment does not meet the requirements for biodegradable implants, hindering its clinical translation. The present study aimed to accelerate the corrosion rate of pure Zn by utilizing acid etching to roughen the surface and increase the substrate surface area. The effects of acid etching on surface morphology, surface roughness, tensile properties, hardness, electrochemical corrosion and degradation behavior, cytocompatibility, direct cell attachment, and biofilm formation were investigated. Interestingly, acid-treated Zn showed an exceptionally high rate of corrosion (∼226-125 µm/year) compared to untreated Zn (∼62 µm/year), attributed to the increased surface roughness (Ra ∼ 1.12 µm) of acid-etched samples. Immersion tests in Hank's solution revealed that acid etching accelerated the degradation rate of Zn samples. In vitro, MC3T3-E1 cell lines in 50 and 25% conditioned media extracts of treated samples showed good cytocompatibility. Reduced bacterial adhesion, biofilm formation, and dispersion were observed for Staphylococci aureus biofilms cultured on acid-etched pure Zn substrates. These results suggest that the surface modification of biodegradable pure Zn metals by acid etching markedly increases the translation potential of zinc for various biomedical applications.

Finite element analysis of the performance of additively manufactured scaffolds for scapholunate ligament reconstruction.

Rupture of the scapholunate interosseous ligament can cause the dissociation of scaphoid and lunate bones, resulting in impaired wrist function. Current treatments (e.g., tendon-based surgical reconstruction, screw-based fixation, fusion, or carpectomy) may restore wrist stability, but do not address regeneration of the ruptured ligament, and may result in wrist functional limitations and osteoarthritis. Recently a novel multiphasic bone-ligament-bone scaffold was proposed, which aims to reconstruct the ruptured ligament, and which can be 3D-printed using medical-grade polycaprolactone. This scaffold is composed of a central ligament-scaffold section and features a bone attachment terminal at either end. Since the ligament-scaffold is the primary load bearing structure during physiological wrist motion, its geometry, mechanical properties, and the surgical placement of the scaffold are critical for performance optimisation. This study presents a patient-specific computational biomechanical evaluation of the effect of scaffold length, and positioning of the bone attachment sites. Through segmentation and image processing of medical image data for natural wrist motion, detailed 3D geometries as well as patient-specific physiological wrist motion could be derived. This data formed the input for detailed finite element analysis, enabling computational of scaffold stress and strain distributions, which are key predictors of scaffold structural integrity. The computational analysis demonstrated that longer scaffolds present reduced peak scaffold stresses and a more homogeneous stress state compared to shorter scaffolds. Furthermore, it was found that scaffolds attached at proximal sites experience lower stresses than those attached at distal sites. However, scaffold length, rather than bone terminal location, most strongly influences peak stress. For each scaffold terminal placement configuration, a basic metric was computed indicative of bone fracture risk. This metric was the minimum distance from the bone surface to the internal scaffold bone terminal. Analysis of this minimum bone thickness data confirmed further optimisation of terminal locations is warranted.

Evaluation of surface layer stability of surface-modified polyester biomaterials.

Surface modification of biomaterials is a strategy used to improve cellular and in vivo outcomes. However, most studies do not evaluate the lifetime of the introduced surface layer, which is an important aspect affecting how a biomaterial will interact with a cellular environment both in the short and in the long term. This study evaluated the surface layer stability in vitro in buffer solution of materials produced from poly(lactic-co-glycolic acid) (50:50) and polycaprolactone modified by hydrolysis and/or grafting of hydrophilic polymers using grafting from approaches. The data presented in this study highlight the shortcomings of using model substrates (e.g., spun-coated films) rather than disks, particles, and scaffolds. It also illustrates how similar surface modification strategies in some cases result in very different lifetimes of the surface layer, thus emphasizing the need for these studies as analogies cannot always be drawn.