Incorporation of fast dissolving glucose porogens and poly(lactic-co-glycolic acid) microparticles within calcium phosphate cements for bone tissue regeneration

Evaluation of physicochemical property changes in 3D-printed biodegradable medical devices under simulated oral physiological conditions

Biodegradable medical devices undergo degradation following implantation, potentially leading to clinical failure. Consequently, it is necessary to assess the change in their properties post-implantation. However, a standardized method for the precise evaluation of the changes in their physicochemical properties is currently lacking. In this study, we aimed to establish precisely simulated oral physiological conditions (SOPCs) and investigate the physicochemical property changes to predict the performance alterations of biodegradable dental barrier membranes (BDBMs) following human implantation. We investigated changes in physicochemical properties of BDBM after exposure to SOPC for 24 weeks. When BDBM was exposed to SOPC for 24 weeks, there was a significant decrease in mass (-1.37%), molecular weight (-19.54%) and tensile load (-72.84%). Among the physicochemical properties, molecular weight decreased similarly after 24 weeks of implantation in rats (-15.78%) and after 24 weeks of exposure to SOPC (-19.54%). Changes in the physicochemical properties of BDBM in simulatedin vitrooral conditions and in thein vivoenvironment were similar. Overall, the evaluation of physicochemical property changes after exposing BDBM to the proposed SOPC demonstrates novelty in its ability to accurately predict performance changes post-implantation. This approach may provide significant insights not only for the development of BDBM but also for various types of biodegradable medical devices.

Osteoporotic Bone Regeneration via Plenished Biomimetic PLGA Scaffold with Sequential Release System

Achieving satisfactory bone tissue regeneration in osteoporotic patients with ordinary biomaterials is challenging because of the decreased bone mineral density and aberrant bone microenvironment. In addressing this issue, a biomimetic scaffold (PMEH/SP), incorporating 4-hexylresorcinol (4HR), and substance P (SP) into the poly(lactic-go-glycolic acid) (PLGA) scaffold with magnesium hydroxide (M) and extracellular matrix (E) is introduced, enabling the consecutive release of bioactive agents. 4HR and SP induced the phosphorylation of p38 MAPK and ERK in human umbilical vein endothelial cells (HUVECs), thereby upregulating VEGF expression level. The migration and tube-forming ability of endothelial cells can be promoted by the scaffold, which accelerates the formation and maturation of the bone. Moreover, 4HR played a crucial role in the inhibition of osteoclastogenesis by interrupting the IκB/NF-κB signaling pathway and exhibiting SP, thereby enhancing the migration and angiogenesis of HUVECs. Based on such a synergistic effect, osteoporosis can be suppressed, and bone regeneration can be achieved by inhibiting the RANKL pathway in vitro and in vivo, which is a commonly known mechanism of bone physiology. Therefore, the study presents a promising approach for developing a multifunctional regenerative material for sophisticated osteoporotic bone regeneration.

Novel Double Hybrid-Type Bone Cements Based on Calcium Phosphates, Chitosan and Citrus Pectin

In this work, the influence of the liquid phase composition on the physicochemical properties of double hybrid-type bone substitutes was investigated. The solid phase of obtained biomicroconcretes was composed of highly reactive α-tricalcium phosphate powder (α-TCP) and hybrid hydroxyapatite/chitosan granules (HA/CTS). Various combinations of disodium phosphate (Na2HPO4) solution and citrus pectin gel were used as liquid phases. The novelty of this study is the development of double-hybrid materials with a dual setting system. The double hybrid phenomenon is due to the interactions between polycationic polymer (chitosan in hybrid granules) and polyanionic polymer (citrus pectin). The chemical and phase composition (FTIR, XRD), setting times (Gillmore needles), injectability, mechanical strength, microstructure (SEM) and chemical stability in vitro were studied. The setting times of obtained materials ranged from 4.5 to 30.5 min for initial and from 7.5 to 55.5 min for final setting times. The compressive strength varied from 5.75 to 13.24 MPa. By incorporating citrus pectin into the liquid phase of the materials, not only did it enhance their physicochemical properties, but it also resulted in the development of fully injectable materials featuring a dual setting system. It has been shown that the properties of materials can be controlled by using the appropriate ratio of citrus pectin in the liquid phase.

Multi-modulation of immune-inflammatory response using bioactive molecule-integrated PLGA composite for spinal fusion

Despite current developments in bone substitute technology for spinal fusion, there is a lack of adequate materials for bone regeneration in clinical applications. Recombinant human bone morphogenetic protein-2 (rhBMP-2) is commercially available, but a severe inflammatory response is a known side effect. Bone graft substitutes that enhance osteogenesis without adverse effects are needed. We developed a bioactive molecule-laden PLGA composite with multi-modulation for bone fusion. This bioresorbable composite scaffold was considered for bone tissue engineering. Among the main components, magnesium hydroxide (MH) aids in reduction of acute inflammation affecting disruption of new bone formation. Decellularized bone extracellular matrix (bECM) and demineralized bone matrix (DBM) composites were used for osteoconductive and osteoinductive activities. A bioactive molecule, polydeoxyribonucleotide (PDRN, PN), derived from trout was used for angiogenesis during bone regeneration. A nano-emulsion method that included Span 80 was used to fabricate bioactive PLGA-MH-bECM/DBM-PDRN (PME2/PN) composite to obtain a highly effective and safe scaffold. The synergistic effect provided by PME2/PN improved not only osteogenic and angiogenic gene expression for bone fusion but also improved immunosuppression and polarization of macrophages that were important for bone tissue repair, using a rat model of posterolateral spinal fusion (PLF). It thus had sufficient biocompatibility and bioactivity for spinal fusion.

Synthesis and characterization of a calcium phosphate bone cement with quercetin-containing PEEK/PLGA microparticles

This study aimed to describe the synthesis and characterization of a calcium phosphate cement (CPC) with polyetheretherketone/poly (lactic-co-glycolic) acid (PEEK/PLGA) micro-particles containing quercetin. CPC powder was synthesized by mixing dicalcium phosphate anhydrate and tetracalcium phosphate. To synthesize PEEK/PLGA microparticles, PLGA85:15 was mixed with 90 wt% PEEK. The weight ratio of quercetin/PLGA/PEEK was 1:9:90 wt%. PEEK/PLGA/quercetin microparticles with 3, 5, and 6 wt% was added to CPC. The setting time, compressive strength, drug release profile, solubility, pH, and porosity of synthesized cement were evaluated. The morphology and physicochemical properties of particles was analyzed by scanning electron microscopy, Fourier-transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and inductively coupled plasma. Cytotoxicity was assessed by the methyl thiazolyl tetrazolium assay using dental pulp stem cells. Expression of osteoblastic differentiation genes was evaluated by real-time polymerase chain reaction. Data were analyzed by one-way ANOVA and Tukey's test (alpha = 0.05). The setting time of 3 wt% CPC was significantly longer than 5 and 6 wt% CPC (P< 0.001). The 6 wt% CPC had significantly higher compressive strength than other groups (P= 0.001). The release of quercetin from CPCs increased for 5 d, and then reached a plateau. XRD and FTIR confirmed the presence of hydroxyapatite in cement composition. Significantly higher expression of osteocalcin (OCN) and osteopontin (OPN) was noted in 3 wt% and 6 wt% CPCs. Addition of quercetin-containing PEEK/PLGA microparticles to CPC enhanced its compressive strength, decreased its setting time, enabled controlled drug release, and up-regulated OPN and OCN.

Synthetic materials in craniofacial regenerative medicine: A comprehensive overview

The state-of-the-art approach to regenerating different tissues and organs is tissue engineering which includes the three parts of stem cells (SCs), scaffolds, and growth factors. Cellular behaviors such as propagation, differentiation, and assembling the extracellular matrix (ECM) are influenced by the cell's microenvironment. Imitating the cell's natural environment, such as scaffolds, is vital to create appropriate tissue. Craniofacial tissue engineering refers to regenerating tissues found in the brain and the face parts such as bone, muscle, and artery. More biocompatible and biodegradable scaffolds are more commensurate with tissue remodeling and more appropriate for cell culture, signaling, and adhesion. Synthetic materials play significant roles and have become more prevalent in medical applications. They have also been used in different forms for producing a microenvironment as ECM for cells. Synthetic scaffolds may be comprised of polymers, bioceramics, or hybrids of natural/synthetic materials. Synthetic scaffolds have produced ECM-like materials that can properly mimic and regulate the tissue microenvironment's physical, mechanical, chemical, and biological properties, manage adherence of biomolecules and adjust the material's degradability. The present review article is focused on synthetic materials used in craniofacial tissue engineering in recent decades.

Injectable bone cement containing carboxymethyl cellulose microparticles as a silver delivery system able to reduce implant-associated infection risk

In the challenging quest for a solution to reduce the risk of implant-associated infections in bone substitution surgery, the use of silver ions is promising regarding its broad spectrum on planktonic, sessile as well as multiresistant bacteria. In view of controlling its delivery in situ at the desired dose, we investigated its encapsulation in carboxymethyl cellulose (CMC) microparticles by spray-drying and included the latter in the formulation of a self-setting calcium phosphate bone cement. We implemented an original step-by-step methodology starting from the in vitro study of the antibacterial properties and cytotoxicity of two silver salts of different solubility in aqueous medium and then in the cement to determine the range of silver loading able to confer anti-biofilm and non-cytotoxic properties to the biomaterial. A dose-dependent efficiency of silver was demonstrated on the main species involved in bone-implant infection (S. aureus and S. epidermidis). Loading silver in microspheres instead of loading it directly inside the cement permitted to avoid undesired silver-cement interactions during setting and led to a faster release of silver, i.e. to a higher dose released within the first days combining anti-biofilm activity and preserved cytocompatibility. In addition, a combined interest of the introduction of about 10% (w/w) silver-loaded CMC microspheres in the cement formulation was demonstrated leading to a fully injectable and highly porous (77%) cement, showing a compressive strength analogous to cancellous bone. This injectable silver-loaded biomimetic composite cement formulation constitutes a versatile bone substitute material with tunable drug delivery properties, able to fight against bone implant associated infection. STATEMENT OF SIGNIFICANCE: This study is based on two innovative scientific aspects regarding the literature: i) Choice of silver ions as antibacterial agent combined with their way of incorporation: Carboxymethylcellulose has never been tested into bone cement to control its drug loading and release properties. ii) Methodology to formulate an antibacterial and injectable bone cement: original and multidisciplinary step-by-step methodology to first define, through (micro)biological tests on two silver salts with different solubilities, the targeted range of silver dose to include in carboxymethylcellulose microspheres and, then optimization of silver-loaded microparticles processing to fulfill requirements (encapsulation efficiency and size). The obtained fully injectable composite controls the early delivery of active dose of silver (from 3 h and over 2 weeks) able to fight against bone implant-associated infections.

A Bibliometric Analysis of the Global Trend of Using Alginate, Gelatine, and Hydroxyapatite for Bone Tissue Regeneration Applications

Collecting information from previous investigations and expressing it in a scientometrics study can be a priceless guide to getting a complete overview of a specific research area. The aim of this study is to explore the interrelated connection between alginate, gelatine, and hydroxyapatite within the scope of bone tissue and scaffold. A review of traditional literature with data mining procedures using bibliometric analyses was considered to identify the evolution of the selected research area between 2009 and 2019. Bibliometric methods and knowledge visualization technologies were implemented to investigate diverse publications based on the following indicators: year of publication, document type, language, country, institution, author, journal, keyword, and number of citations. An analysis using a bibliometric study found that 7446 papers were located with the keywords "bone tissue" and "scaffold", and 1767 (alginate), 185 (gelatine), 5658 (hydroxyapatite) papers with those specific sub keywords. The number of publications that relate to "tissue engineering" and bone more than doubled between 2009 (1352) and 2019 (2839). China, the United States and India are the most productive countries, while Sichuan University and the Chinese Academy of Science from China are the most important institutions related to bone tissue scaffold. Materials Science and Engineering C is the most productive journal, followed by the Journal of Biomedical Materials Research Part A. This paper is a starting point, providing the first bibliometric analysis study of bone tissue and scaffold considering alginate, gelatine and hydroxyapatite. A bibliometric analysis would greatly assist in giving a scientific insight to support desired future research work, not only associated with bone tissue engineering applications. It is expected that the analysis of alginate, gelatine and hydroxyapatite in terms of 3D bioprinting, clinical outcomes, scaffold architecture, and the regenerative medicine approach will enhance the research into bone tissue engineering in the near future. Continued studies into these research fields are highly recommended.

A Biphasic Calcium Phosphate Cement Enhances Dentin Regeneration by Dental Pulp Stem Cells and Promotes Macrophages M2 Phenotype In Vitro

Calcium phosphate cement (CPC) is promising for bone and dentin repair and regeneration. However, there has been no report of biphasic CPC for inducing dentin regeneration. The aim of this study was to develop a novel biphasic CPC containing β-tricalcium phosphate (β-TCP), and investigate its effects on odontogenic differentiation of human dental pulp stem cells (hDPSCs) and macrophage polarization. New biphasic CPC was formulated with different ratios of β-TCP to an equimolar mixture of tetracalcium phosphate and dicalcium phosphate anhydrous. Mechanical properties, biocompatibility, and odontogenic differentiation induction ability of the cements and the inflammatory reaction to the cements were examined. A series of CPC containing β-TCP were developed. CPC with 20% β-TCP exhibited homogeneity and injectability, an acceptable setting time, and a twofold increase in compressive strength. Significant increases in hDPSCs' alkaline phosphatase activity, mineral deposit, DMP1 and DSPP gene, and protein expressions were obtained for 20% TCP-CPC, compared with traditional CPC (p < 0.01). The addition of β-TCP did not promote macrophage polarization to the proinflammation phenotype. The addition of 10% and 20% β-TCP promoted macrophage polarization to the anti-inflammatory phenotype. In conclusion, a biphasic β-TCP-modified CPC was developed for the first time, demonstrating substantially increased dentin regeneration capability, while promoting macrophages to an anti-inflammation phenotype. The novel biphasic CPC is promising for tooth tissue engineering and dentin regeneration applications.

Calcium phosphate cements: Optimization toward biodegradability

Synthetic calcium phosphate (CaP) ceramics represent the most widely used biomaterials for bone regenerative treatments due to their biological performance that is characterized by bioactivity and osteoconductive properties. From a clinical perspective, injectable CaP cements (CPCs) are highly appealing, as CPCs can be applied using minimally invasive surgery and can be molded to optimally fill irregular bone defects. Such CPCs are prepared from a powder and a liquid component, which upon mixing form a paste that can be injected into a bone defect and hardens in situ within an appropriate clinical time window. However, a major drawback of CPCs is their poor degradability. Ideally, CPCs should degrade at a suitable pace to allow for concomitant new bone to form. To overcome this shortcoming, control over CPC degradation has been explored using multiple approaches that introduce macroporosity within CPCs. This strategy enables faster degradation of CPC by increasing the surface area available to interact with the biological surroundings, leading to accelerated new bone formation. For a comprehensive overview of the path to degradable CPCs, this review presents the experimental procedures followed for their development with specific emphasis on (bio)material properties and biological performance in pre-clinical bone defect models.

Setting Characteristics and High Compressive Strength of an Anti-washout, Injectable Calcium Phosphate Cement Combined with Thermosensitive Hydrogel

In this work, a thermosensitive poly(D,L-lactide-co-glycolide)-poly(ethylene glycol)-poly(D,L-lactide-co-glycolide) (PLGA-PEG-PLGA) hydrogel was introduced into calcium phosphate cement (CPC) to enhance the anti-washout property of CPC. The effects of the hydrogel on the setting time, injectability, anti-washout property and compressive strength of CPC were thoroughly investigated. The results showed that the hydrogel significantly increased the injectability and anti-washout property of CPC, meanwhile maintained the setting time with an acceptable range. Moreover, the hydrogel improved the initial compressive strength of CPC. The composite cement with 20% v/v hydrogel in the liquid phase showed fine crystals of hydration product, a more compact microstructure and lower porosity compared with control CPC. The analysis of X-ray diffraction (XRD), infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) indicated that suitable volume ratio of hydrogel (20% v/v) in the setting liquid of CPC could promote the formation of hydroxyapatite in the early hydration period. The degradation behavior of the cement was characterized by immersion tests in simulated body fluid. The hydrogel had no adverse effect on the degradation rate of CPC over the immersion period of 23 days. This study indicated that incorporating PLGA-PEG-PLGA hydrogel could be a promising strategy to reinforce the handing properties and initial compressive strength of calcium phosphate cement.

Fluorescent nanoparticles with ultralow chromophore loading for long-term tumor-targeted imaging

Recently, organic dyes with aggregation-induced emission (AIE) have attracted much attention in bioimaging and diagnostics. Relatively, the application of traditional dyes has diminished because of aggregation-caused quenching (ACQ). In this work, we compare the imaging ability of nanoparticle formulations of these two kinds of dyes. Boron dipyrromethene (BODIPY) was chosen as a representative of the ACQ dyes, and an aggregation-induced emission (AIE) dye BPMT was used for comparison. BODIPY and BPMT were entrapped into PEG_5k-PLA_10k to form BODIPY-loaded NPs (BNPs) and BPMT-loaded NPs (ANPs), respectively. In vivo and ex vivo imaging demonstrated that BNP1 with ultralow BODIPY load (0.07%) can effectively accumulate in tumor tissues and enable long-term noninvasive imaging. In contrast, ANP4 with high BPMT load (1.6%) has poor bioimaging ability. In general, our work has certain reference significance for the application of ACQ dyes and AIEgens in bioimaging, diagnostics, and theranostics. STATEMENT OF SIGNIFICANCE: In this work, Boron dipyrromethene (BODIPY) was chosen as a representative of ACQ dyes. As a control, (Z)-2-(4'-(9H-carbazol-9-yl)-[1,1'-biphenyl]-4-yl)-3-(7-(4-(bis(4methoxyphenyl)amino) phenyl) benzo[c] [1,2,5] thiadiazol-4-yl) acrylonitrile (BPMT) was selected as an aggregation-induced emission (AIE) dye. BODIPY and BPMT was entrapped into PEG5k-PLA10k to form BODIPY-loaded NPs (BNPs) and BPMT-loaded NPs (ANPs), respectively. In vivo and ex vivo imaging demonstrated that BNP1 with ultralow BODIPY load (0.07%) can effectively accumulate in tumor tissues and realize long-term noninvasive imaging. The weaknesses of ACQ effect can be converted into advantages by skillful use of nanotechnology, which can not only save the cost but also realize high efficiency targeted cancer imaging.

Injectable Functional Biomaterials for Minimally Invasive Surgery

Injectable materials represent very attractive ready-to-use biomaterials for application in minimally invasive surgical procedures. It is shown that this approach to treat, for example, vertebral fracture, craniofacial defects, or tumor resection has significant clinical potential in the biomedical field. In the last four decades, calcium phosphate cements have been widely used as injectable materials for orthopedic surgery due to their excellent properties in terms of biocompatibility and osteoconductivity. However, few clinical studies have demonstrated certain weaknesses of these cements, which include high viscosity, long degradation time, and difficulties being manipulated. To overcome these limitations, the use of sol-gel technology has been investigated, which has shown good results for synthesis of injectable calcium phosphate-based materials. In the last few decades, injectable hydrogels have gained increasing attention owing to their structural similarities with the extracellular matrix, easy process conditions, and potential applications in minimally invasive surgery. However, the need to protect cells during injection leads to the development of double network injectable hydrogels that are capable of being cross-linked in situ. This review will provide the current state of the art and recent advances in the field of injectable biomaterials for minimally invasive surgery.

Advances in biomaterials for skeletal muscle engineering and obstacles still to overcome

Repair of injured skeletal muscle is a sophisticated process that uses immune, muscle, perivascular, and neural cells. In acute injury, the robust endogenous repair process can facilitate complete regeneration with little to no functional deficit. However, in severe injury, the damage is beyond the capacity for self-repair, often resulting in structural and functional deficits. Aside from the insufficiencies in muscle function, the aesthetic deficits can impact quality of life. Current clinical treatments are significantly limited in their capacity to structurally and functionally repair the damaged skeletal muscle. Therefore, alternative approaches are needed. Biomaterial therapies for skeletal muscle engineering have leveraged natural materials with sophisticated scaffold fabrication techniques to guide cell infiltration, alignment, and differentiation. Advances in biomaterials paired with a standardized and rigorous assessment of resulting tissue formation have greatly advanced the field of skeletal muscle engineering in the last several years. Herein, we discuss the current trends in biomaterials-based therapies for skeletal muscle regeneration and present the obstacles still to be overcome before clinical translation is possible. With millions of people affected by muscle trauma each year, the development of a therapy that can repair the structural and functional deficits after severe muscle injury is pivotal.

Effects of macropore size in carbonate apatite honeycomb scaffolds on bone regeneration

The pore architecture of scaffolds is a critical factor for angiogenesis and bone regeneration. Although the effects of scaffold macropore size have been investigated, most scaffolds feature macropores with poor uniformity and interconnectivity, and other parameters (e.g., microporosity, chemical composition, and strut thickness) differ among scaffolds. To clarify the threshold of effective macropore size, we fabricated honeycomb scaffolds (HCSs) with distinct macropore (i.e., channel) sizes (~100, ~200, and ~300 μm). The HCSs were composed of AB-type carbonate apatite with ~8.5% carbonate ions, i.e., the same composition as human bone mineral. Their honeycomb architecture displayed uniformly sized and orderly arranged channels with extremely high interconnectivity, and all the HCSs displayed ~100-μm-thick struts and 0.06 cm³ g^-1 of micropore volume. The compressive strengths of HCSs with ~100-, ~200-, and ~300-μm channels were higher than those of reported scaffolds, and decreased with increasing channel size: 62 ± 6, 55 ± 9, and 43 ± 8 MPa, respectively. At four weeks after implantation in rabbit femur bone defects, new bone and blood vessels were formed in all the channels of these HCSs. Notably, the ~300-μm channels were extensively occupied by new bone. We demonstrated that high interconnectivity and uniformity of channels can decrease the threshold of effective macropore size, enabling the scaffolds to maintain high mechanical properties and osteogenic ability and serve as implants for weight-bearing areas.

The Effect of the Thermosensitive Biodegradable PLGA⁻PEG⁻PLGA Copolymer on the Rheological, Structural and Mechanical Properties of Thixotropic Self-Hardening Tricalcium Phosphate Cement

The current limitations of calcium phosphate cements (CPCs) used in the field of bone regeneration consist of their brittleness, low injectability, disintegration in body fluids and low biodegradability. Moreover, no method is currently available to measure the setting time of CPCs in correlation with the evolution of the setting reaction. The study proposes that it is possible to improve and tune the properties of CPCs via the addition of a thermosensitive, biodegradable, thixotropic copolymer based on poly(lactic acid), poly(glycolic acid) and poly(ethylene glycol) (PLGA⁻PEG⁻PLGA) which undergoes gelation under physiological conditions. The setting times of alpha-tricalcium phosphate (α-TCP) mixed with aqueous solutions of PLGA⁻PEG⁻PLGA determined by means of time-sweep curves revealed a lag phase during the dissolution of the α-TCP particles. The magnitude of the storage modulus at lag phase depends on the liquid to powder ratio, the copolymer concentration and temperature. A sharp increase in the storage modulus was observed at the time of the precipitation of calcium deficient hydroxyapatite (CDHA) crystals, representing the loss of paste workability. The PLGA⁻PEG⁻PLGA copolymer demonstrates the desired pseudoplastic rheological behaviour with a small decrease in shear stress and the rapid recovery of the viscous state once the shear is removed, thus preventing CPC phase separation and providing good cohesion. Preliminary cytocompatibility tests performed on human mesenchymal stem cells proved the suitability of the novel copolymer/α-TCP for the purposes of mini-invasive surgery.