New prospects in skin regeneration and repair using nanophased hydroxyapatite embedded in collagen nanofibers.

This study reflects an exploitation of a composite matrix produced by electrospinning of collagen and electrospraying of nanophased hydroxyapatite (nanoHA), for skin regeneration applications. The main goal was to evaluate the effect of nanoHA, as source of localized calcium delivery, on human dermal fibroblasts, keratinocytes, and human mesenchymal stem cells (hMSCs) growth, proliferation, differentiation, and extracellular matrix production. This study revealed that calcium ions provided by nanoHA significantly enhanced cellular growth and proliferation rates and prevented adhesion of pathogenic bacteria strains typically found in human skin flora. Moreover, hMSCs were able to differentiate in both osteogenic and adipogenic lineages. Rat subcutaneous implantation of the membranes also revealed that no adverse reaction occurred. Therefore, the mechanically fit composite membrane presents a great potential to be used either as cell transplantation scaffold for skin wound regeneration or as wound dressing material in plastic surgery, burns treatment or skin diseases.

Antibacterial silk fibroin/nanohydroxyapatite hydrogels with silver and gold nanoparticles for bone regeneration.

The rapid emergence of antibiotic resistance is becoming an imminent problem in bone tissue engineering, and therefore biomaterials must be modified to promote the tissue integration before bacterial adhesion. In this work, silk fibroin/nanohydroxyapatite hydrogel was modified with in situ synthesized silver and gold nanoparticles (AgNPs and AuNPs), taking advantage of the tyrosine amino acid. The presence of AgNPs and AuNPs in the hydrogels was characterized by UV spectrophotometer, transmission electron microscopy and thermogravimetric analysis. In vitro antimicrobial studies revealed that hydrogels with AgNPs and AuNPs exhibited significant inhibition ability against both gram-positive and gram-negative bacteria. Cytocompatibility studies carried out using osteoblastic cells revealed that up to 0.5 wt% of AgNPs, and for all concentrations of AuNPs, the hydrogels can be effectively used as antimicrobial materials, without compromising cell behavior. On the basis of the aforementioned observations, these hydrogels are very attractive for bone tissue engineering.

Phase Behaviour and Miscibility Studies of Collagen/Silk Fibroin Macromolecular System in Dilute Solutions and Solid State.

Miscibility is an important issue in biopolymer blends for analysis of the behavior of polymer pairs through the detection of phase separation and improvement of the mechanical and physical properties of the blend. This study presents the formulation of a stable and one-phase mixture of collagen and regenerated silk fibroin (RSF), with the highest miscibility ratio between these two macromolecules, through inducing electrostatic interactions, using salt ions. For this aim, a ternary phase diagram was experimentally built for the mixtures, based on observations of phase behavior of blend solutions with various ratios. The miscibility behavior of the blend solutions in the miscible zones of the phase diagram was confirmed quantitatively by viscosimetric measurements. Assessing the effects of biopolymer mixing ratio and salt ions, before and after dialysis of blend solutions, revealed the importance of ion-specific interactions in the formation of coacervate-based materials containing collagen and RSF blends that can be used in pharmaceutical, drug delivery, and biomedical applications. Moreover, the conformational change of silk fibroin from random coil to beta sheet, in solution and in the final solid films, was detected by circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR), respectively. Scanning electron microscopy (SEM) exhibited alterations of surface morphology for the biocomposite films with different ratios. Surface contact angle measurement illustrated different hydrophobic properties for the blended film surfaces. Differential scanning calorimetry (DSC) showed that the formation of the beta sheet structure of silk fibroin enhances the thermal stability of the final blend films. Therefore, the novel method presented in this study resulted in the formation of biocomposite films whose physico-chemical properties can be tuned by silk fibroin conformational changes by applying different component mixing ratios.

Effects of Line and Pillar Array Microengineered SiO2 Thin Films on the Osteogenic Differentiation of Human Bone Marrow-Derived Mesenchymal Stem Cells.

A primary goal in bone tissue engineering is the design of implants that induce controlled, guided, and rapid healing. The events that normally lead to the integration of an implant into bone and determine the performance of the device occur mainly at the tissue-implant interface. Topographical surface modification of a biomaterial might be an efficient tool for inducing stem cell osteogenic differentiation and replace the use of biochemical stimuli. The main goal of this work was to develop micropatterned bioactive silica thin films to induce the osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (hMSCs) only through topographical stimuli. Line and pillar micropatterns were developed by a combination of sol-gel/soft lithography and characterized by scanning electron microscopy, atomic force microscopy, and contact angle measurements. hMSCs were cultured onto the microfabricated thin films and flat control for up to 21 days under basal conditions. The micropatterned groups induced levels of osteogenic differentiation and expression of osteoblast-associated markers higher than those of the flat controls. Via comparison of the micropatterns, the pillars caused a stronger response of the osteogenic differentiation of hMSCs with a higher level of expression of osteoblast-associated markers, ALP activity, and extracellular matrix mineralization after the cells had been cultured for 21 days. These findings suggest that specific microtopographic cues can direct hMSCs toward osteogenic differentiation.

Local Antibiotic Delivery Ceramic Bone Substitutes for the Treatment of Infected Bone Cavities and Bone Regeneration: A Systematic Review on What We Have Learned from Animal Models.

AIMS: the focus of this study is to evaluate if the combination of an antibiotic with a ceramic biomaterial is effective in treating osteomyelitis in an infected animal model and to define which model and protocol are best suited for in vivo experiments of local bone infection treatment. METHODS: a systematic review was carried out based on PRISMA statement guidelines. A PubMed search was conducted to find original papers on animal models of bone infections using local antibiotic delivery systems with the characteristics of bone substitutes. Articles without a control group, differing from the experimental group only by the addition of antibiotics to the bone substitute, were excluded. RESULTS: a total of 1185 records were retrieved, and after a three-step selection, 34 papers were included. Six manuscripts studied the effect of antibiotic-loaded biomaterials on bone infection prevention. Five articles studied infection in the presence of foreign bodies. In all but one, the combination of an antibiotic with bioceramic bone substitutes tended to prevent or cure bone infection while promoting biomaterial osteointegration. CONCLUSIONS: this systematic review shows that the combination of antibiotics with bioceramic bone substitutes may be appropriate to treat bone infection when applied locally. The variability of the animal models, time to develop an infection, antibiotic used, way of carrying and releasing antibiotics, type of ceramic material, and endpoints limits the conclusions on the ideal therapy, enhancing the need for consistent models and guidelines to develop an adequate combination of material and antimicrobial agent leading to an effective human application.

Magnetic Bone Tissue Engineering: Reviewing the Effects of Magnetic Stimulation on Bone Regeneration and Angiogenesis.

Bone tissue engineering emerged as a solution to treat critical bone defects, aiding in tissue regeneration and implant integration. Mainly, this field is based on the development of scaffolds and coatings that stimulate cells to proliferate and differentiate in order to create a biologically active bone substitute. In terms of materials, several polymeric and ceramic scaffolds have been developed and their properties tailored with the objective to promote bone regeneration. These scaffolds usually provide physical support for cells to adhere, while giving chemical and physical stimuli for cell proliferation and differentiation. Among the different cells that compose the bone tissue, osteoblasts, osteoclasts, stem cells, and endothelial cells are the most relevant in bone remodeling and regeneration, being the most studied in terms of scaffold-cell interactions. Besides the intrinsic properties of bone substitutes, magnetic stimulation has been recently described as an aid in bone regeneration. External magnetic stimulation induced additional physical stimulation in cells, which in combination with different scaffolds, can lead to a faster regeneration. This can be achieved by external magnetic fields alone, or by their combination with magnetic materials such as nanoparticles, biocomposites, and coatings. Thus, this review is designed to summarize the studies on magnetic stimulation for bone regeneration. While providing information regarding the effects of magnetic fields on cells involved in bone tissue, this review discusses the advances made regarding the combination of magnetic fields with magnetic nanoparticles, magnetic scaffolds, and coatings and their subsequent influence on cells to reach optimal bone regeneration. In conclusion, several research works suggest that magnetic fields may play a role in regulating the growth of blood vessels, which are critical for tissue healing and regeneration. While more research is needed to fully understand the relationship between magnetism, bone cells, and angiogenesis, these findings promise to develop new therapies and treatments for various conditions, from bone fractures to osteoporosis.

Vancomycin-Loaded, Nanohydroxyapatite-Based Scaffold for Osteomyelitis Treatment: In Vivo Rabbit Toxicological Tests and In Vivo Efficacy Tests in a Sheep Model.

The treatment for osteomyelitis consists of surgical debridement, filling of the dead space, soft tissue coverage, and intravenous administration of antimicrobial (AM) agents for long periods. Biomaterials for local delivery of AM agents, while providing controllable antibiotic release rates and simultaneously acting as a bone scaffold, may be a valuable alternative; thus, avoiding systemic AM side effects. V-HEPHAPC is a heparinized nanohydroxyapatite (nHA)/collagen biocomposite loaded with vancomycin that has been previously studied and tested in vitro. It enables a vancomycin-releasing profile with an intense initial burst, followed by a sustained release with concentrations above the Minimum Inhibitory Concentration (MIC) for MRSA. In vitro results have also shown that cellular viability is not compromised, suggesting that V-HEPHAPC granules may be a promising alternative device for the treatment of osteomyelitis. In the present study, V-HEPHAPC (HEPHAPC with vancomycin) granules were used as a vancomycin carrier to treat MRSA osteomyelitis. First, in vivo Good Laboratory Practice (GLP) toxicological tests were performed in a rabbit model, assuring that HEPHAPC and V-HEPHAPC have no relevant side effects. Second, V-HEPHAPC proved to be an efficient drug carrier and bone substitute to control MRSA infection and simultaneously reconstruct the bone cavity in a sheep model.

Nanomaterials in cancer: Reviewing the combination of hyperthermia and triggered chemotherapy.

Nanoparticle mediated hyperthermia has been explored as a method to increase cancer treatment efficacy by heating tumours inside-out. With that purpose, nanoparticles have been designed and their properties tailored to respond to external stimuli and convert the supplied energy into heat, therefore inducing damage to tumour cells. Moreover, the combination of hyperthermia with chemotherapy has been described as a more effective strategy due to the synergy between the high temperature and the drug's effects, also associated with a remote controlled and on-demand drug release. In this review, the methods behind nanoparticle mediated hyperthermia, namely material design, external stimuli response and energy conversion will be discussed and critically analysed. We will address the most relevant studies on hyperthermia and temperature triggered drug release for cancer treatment. Finally, the advantages, difficulties and challenges of this therapeutic strategy will be discussed, while giving insight for future developments.

Design and surface characterization of micropatterned silica coatings for zirconia dental implants.

The use of zirconia as an alternative biomaterial for titanium implants has been increasing due to its biocompatibility, favorable aesthetic features, less potential for early plaque accumulation and mechanical properties. Despite the developed efforts, strategies to promote an effective osseointegration are still enough. In this sense and combining the silica properties to improve bone formation with the micropatterning guidance characteristics, silica coatings with micropatterns were designed and evaluated regarding their hydrophilicity and integrity through resistance to scratch and friction tests against femoral bone plates (simulating implant insertion). A combined sol-gel and soft-lithography techniques were used to produce silica coatings onto zirconia substrates and different techniques were used to characterize the micropatterned silica coatings. The results revealed that the production of lines and pillars micropatterns increases the surface roughness (Ra values) and improves the surface strength adhesion. Through the scratch test, it was possible to verify that the integrity and topography characteristics of all micropatterned coatings were not significantly affected after the friction test meaning that their function is not compromised after implant insertion. Additionally, the lines micropattern was the one that presented the highest hydrophilicity for distilled water, thus being a promising surface to promote improved osseointegration. The combined use of different surface micropatterns could potentially be used to guide bone apposition and avoiding peri-implantitis.

Magnetic mesoporous silica nanoparticles as a theranostic approach for breast cancer: Loading and release of the poorly soluble drug exemestane.

Exemestane has a limited aqueous solubility that leads to a very high variability in absorption when administrated orally. It is crucial to develop strategies to increase the solubility and bioavailability of this drug. To overcome these issues, the aim of the present work was the development of magnetic silica mesoporous nanoparticles (IOMSNs) to carry and release exemestane. Furthermore, these nanoparticles could be also used as Magnetic Resonance Imaging (MRI) contrast agents for treatment monitorization and tumor detection. MRI analysis showed that IOMSNs present a concentration dependent contrast effect, revealing their potential for MRI applications. Also, IOMSNs present a very good polydispersity (0.224) and nanometric range size (137.2 nm). It was confirmed that the nucleus is composed by magnetite and the silica coating presents tubes with MCM-41-like hexagonal structure. Both iron oxide nanoparticles and iron oxide mesoporous silica nanoparticles were not toxic in cell culture for 24 h. Exemestane was successful released for 72 h following a typical sustained release pattern, achieving a very high loading capacity (37.7%) and in vitro release of 98.8%. Taking into account the results it is possible to conclude that IOMSNs have a high potential to be used as theranostic for intravenous breast cancer treatment with exemestane.

Scaffolds Loaded with Dialdehyde Chitosan and Collagen-Their Physico-Chemical Properties and Biological Assessment.

In this work, dialdehyde chitosan (DAC) and collagen (Coll) scaffolds have been prepared and their physico-chemical properties have been evaluated. Their structural properties were studied by Fourier Transform Infrared Spectroscopy with Attenuated Internal Reflection (FTIR-ATR) accompanied by evaluation of thermal stability, porosity, density, moisture content and microstructure by Scanning Electron Microscopy-SEM. Additionally, cutaneous assessment using human epidermal keratinocytes (NHEK), dermal fibroblasts (NHDF) and melanoma cells (A375 and G-361) was performed. Based on thermal studies, two regions in DTG curves could be distinguished in each type of scaffold, what can be assigned to the elimination of water and the polymeric structure degradation of the materials components. The type of scaffold had no major effect on the porosity of the materials, but the water content of the materials decreased with increasing dialdehyde chitosan content in subjected matrices. Briefly, a drop in proliferation was noticed for scaffolds containing 20DAC/80Coll compared to matrices with collagen alone. Furthermore, increased content of DAC (50DAC/50Coll) either significantly induced the proliferation rate or maintains its ratio compared to the control matrix. This delivery is a promising technique for additional explorations targeting therapies in regenerative dermatology. The using of dialdehyde chitosan as one of the main scaffolds components is the novelty in terms of bioengineering.

The effect of slurry preparation methods on biaxial flexural strength of dental porcelain.

STATEMENT OF PROBLEM: One-step and incremental mixing procedures are currently used to produce dental ceramic pastes. In the ceramic industry, high quality is obtained using one-step mixing, but in dentistry, the best method has not been yet determined. PURPOSE: The purpose of this study is to evaluate the effects of 2 mixing techniques on the biaxial flexural strength and microstructure of dental porcelain. MATERIAL AND METHODS: Feldspathic porcelain discs (2 × 15 mm in diameter) were produced and divided according to the ceramic paste preparation method, powder-liquid incremental mixing group (n=50) or one-step mixing, as a control group (n=50). Specimens were tested for biaxial flexural strength and characterized using porosimetry, relative humidity, SEM/EDS, XRD, and FT-IR analyses. Statistical analysis was conducted using Weibull statistics. The Weibull modulus, characteristic strength and relative humidity were compared between groups, using Student's t-test and Mann-Whitney U test (α=.05). RESULTS: The powder-liquid incremental mixing group showed significantly higher values (SD) of Weibull modulus (6.74 (0.70), P<.001) and characteristic strength (79.87 (2.01) MPa, P<.001) when compared to the one-step mixing group (4.94 (0.94) and 75.95 (2.61) MPa). Significantly lower mean (SD) relative humidity values (P=.009) were found for powder-liquid incremental mixing group (20% (0.5%)) compared to one-step mixing group (22% (1%)). XRD spectra showed that the one-step mixing group produced higher amounts of the amorphous phase. CONCLUSIONS: Specimens produced by the incremental mixing technique showed higher biaxial flexural strength than one-step mixing.

Biomaterials with Potential Use in Bone Tissue Regeneration-Collagen/Chitosan/Silk Fibroin Scaffolds Cross-Linked by EDC/NHS.

Blending of different biopolymers, e.g., collagen, chitosan, silk fibroin and cross-linking modifications of these mixtures can lead to new materials with improved physico-chemical properties, compared to single-component scaffolds. Three-dimensional scaffolds based on three-component mixtures of silk fibroin, collagen and chitosan, chemically cross-linked, were prepared and their physico-chemical and biological properties were evaluated. A mixture of EDC (N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride) and NHS (N-hydroxysuccinimide) was used as a cross-linking agent. FTIR was used to observe the position of the peaks characteristic for collagen, chitosan and silk fibroin. The following properties depending on the scaffold structure were studied: swelling behavior, liquid uptake, moisture content, porosity, density, and mechanical parameters. Scanning Electron Microscopy imaging was performed. Additionally, the biological properties of these materials were assessed, by metabolic activity assay. The results showed that the three-component mixtures, cross-linked by EDC/NHS and prepared by lyophilization method, presented porous structures. They were characterized by a high swelling degree. The composition of scaffolds has an influence on mechanical properties. All of the studied materials were cytocompatible with MG-63 osteoblast-like cells.

Bioengineered Fluorescent Nanoprobe Conjugates for Tracking Human Bone Cells: In Vitro Biocompatibility Analysis.

Herein, we validated novel functionalized hybrid semiconductor bioconjugates made of fluorescent quantum dots (QD) with the surface capped by chitosan (polysaccharide) and chemically modified with O-phospho-L-serine (OPS) that are biocompatible with different human cell sources. The conjugation with a directing signaling molecule (OPS) allows preferential accumulation in human bone mesenchymal stromal cells (HBMSC). The chitosan (Chi) shell with the fluorescent CdS core was characterized by spectroscopical (UV spectrophotometry and photoluminescence), by morphological techniques (Transmission Electron Microscopy (TEM)) and showed small size (ø 2.3 nm) and a stable photoluminescence emission band. The in vitro biocompatibility results were not dependent on the polysaccharide chain length (Chi with higher and lower molecular weight) but were remarkably affected by the surface modification (Chi or Chi-OPS). In addition, the efficiency of nanoparticles uptake by the cells was dependent on cells nature (human primary cells or cell lines) and tissue source (bone or skin) in the presence or absence of the OPS modification. The complex cellular uptake pathways involved in the cell labeling with the nanoparticles do not interfere on the normal cellular biology (adhesion and proliferation), osteogenic differentiation, and gene expression. The bone cells particles uptake evaluation showed a possible pathway by Caveolin-1 that regulates cell transduction in the membrane's Caveolae. Caveolae mediates non-specific endocytosis, and it is upregulated in HBMSC. The OPS-modified nanoparticles promoted an intense intracellular trafficking by the HBMSCs that showed late-osteoblast phenotype with an increase of extracellular matrix (ECM) mineralization (Alizarin red and Von Kossa staining for calcium phosphate crystals). In this work, the OPS modified bioconjugated QD proved to be a reliable and stable fluorescent bioprobe for cell imaging and targeting research that could also help in clarifying some cellular mechanisms of particles intracellular traffic through the cytoplasmic membrane and osteogenic differentiation induction. The in vitro HBMSC's biocompatibility responses indicated that the OPS-modified chitosan QDs have a prospective future in laboratory and pre-clinical applications such as bioimaging analysis and for ex-vivo cellular evaluation of biomedical implants.

Combining local antibiotic delivery with heparinized nanohydroxyapatite/collagen bone substitute: A novel strategy for osteomyelitis treatment.

Osteomyelitis is a major challenge in bone surgery and conventional treatment is frequently ineffective to control the infection, with an alternative approach being required. In the present work, a heparinized nanohydroxyapatite/collagen biocomposite was produced in granular form, and loaded with vancomycin, to work as a local drug delivery system for osteomyelitis and as a bone substitute. This strategy involves the local delivery of high concentrations of vancomycin, to eradicate the infection. Additionally, these granules work as a scaffold with regenerative properties, to induce bone regeneration after antibiotic release. The heparinized nanohydroxyapatite/collagen granular bone substitute was produced using two different sintering temperatures to study their effect on granules properties and on vancomycin release profile. Morphological, topographic, chemical and mechanical characterization were carried out for granules sintered at both temperatures and some relevant differences were found. The mechanical strength was increased by several orders of magnitude with increasing sintering temperature, being able to maintain their porous macrostructure and withstand important processes for their commercialization such as packaging, shipping and surgical manipulation. The nanohydroxyapatite/collagen granules were able to release high concentrations of vancomycin, always above MIC, for 19 days. The released antibiotic was able to eradicate both planktonic and sessile methicillin-resistant Staphylococcus aureus. The cytotoxicity was assessed according to ISO 10993-5:2009 and the granules sintered at higher temperature showed no cytotoxic effect. Considering these results nanohydroxyapatite/collagen biocomposite loaded with vancomycin is a promising solution for osteomyelitis treatment.

Emerging Lab-on-a-Chip Approaches for Liquid Biopsy in Lung Cancer: Status in CTCs and ctDNA Research and Clinical Validation.

Despite the intensive efforts dedicated to cancer diagnosis and treatment, lung cancer (LCa) remains the leading cause of cancer-related mortality, worldwide. The poor survival rate among lung cancer patients commonly results from diagnosis at late-stage, limitations in characterizing tumor heterogeneity and the lack of non-invasive tools for detection of residual disease and early recurrence. Henceforth, research on liquid biopsies has been increasingly devoted to overcoming these major limitations and improving management of LCa patients. Liquid biopsy is an emerging field that has evolved significantly in recent years due its minimally invasive nature and potential to assess various disease biomarkers. Several strategies for characterization of circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA) have been developed. With the aim of standardizing diagnostic and follow-up practices, microfluidic devices have been introduced to improve biomarkers isolation efficiency and specificity. Nonetheless, implementation of lab-on-a-chip platforms in clinical practice may face some challenges, considering its recent application to liquid biopsies. In this review, recent advances and strategies for the use of liquid biopsies in LCa management are discussed, focusing on high-throughput microfluidic devices applied for CTCs and ctDNA isolation and detection, current clinical validation studies and potential clinical utility.

Translational Research for Orthopedic Bone Graft Development.

Designing biomaterials for bone-substitute applications is still a challenge regarding the natural complex structure of hard tissues. Aiming at bone regeneration applications, scaffolds based on natural collagen and synthetic nanohydroxyapatite were developed, and they showed adequate mechanical and biological properties. The objective of this work was to perform and evaluate a scaled-up production process of this porous biocomposite scaffold, which promotes bone regeneration and works as a barrier for both fibrosis and the proliferation of scar tissue. The material was produced using a prototype bioreactor at an industrial scale, instead of laboratory production at the bench, in order to produce an appropriate medical device for the orthopedic market. Prototypes were produced in porous membranes that were e-beam irradiated (the sterilization process) and then analysed by scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), dynamic mechanical analysis (DMA), cytotoxicity tests with mice fibroblasts (L929), human osteoblast-like cells (MG63) and human MSC osteogenic differentiation (HBMSC) with alkaline phosphatase (ALP) activity and qPCR for osteogenic gene expression. The prototypes were also implanted into critical-size bone defects (rabbits' tibia) for 5 and 15 weeks, and after that were analysed by microCT and histology. The tests performed for the physical characterization of the materials showed the ability of the scaffolds to absorb and retain water-based solvents, as well as adequate mechanical resistance and viscoelastic properties. The cryogels had a heteroporous morphology with microporosity and macroporosity, which are essential conditions for the interaction between the cells and materials, and which consequently promote bone regeneration. Regarding the biological studies, all of the studied cryogels were non-cytotoxic by direct or indirect contact with cells. In fact, the scaffolds promoted the proliferation of the human MSCs, as well as the expression of the osteoblastic phenotype (osteogenic differentiation). The in vivo results showed bone tissue ingrowth and the materials' degradation, filling the critical bone defect after 15 weeks. Before and after irradiation, the studied scaffolds showed similar properties when compared to the results published in the literature. In conclusion, the material production process upscaling was optimized and the obtained prototypes showed reproducible properties relative to the bench development, and should be able to be commercialized. Therefore, it was a successful effort to harness knowledge from the basic sciences to produce a new biomedical device and enhance human health and wellbeing.

Clarifying the Tooth-Derived Stem Cells Behavior in a 3D Biomimetic Scaffold for Bone Tissue Engineering Applications.

Massive amounts of cell are needed for creating tissue engineered 3D constructs, which often requires culture on scaffolds under dynamic conditions to facilitate nutrients and oxygen diffusion. Dynamic cultures are expected to improve cell viability and proliferation rate, when compared to static conditions. However, cells from distinct types and/or tissues sources may respond differently to external stimuli and be incompatible with culture under mechanical shear stress. The first aim of this work was to show that dental stem cells are a valuable source for improving bone regeneration potential of artificial grafts. Mesenchymal stem/stromal cells (MSCs) were isolated from human dental follicle (hDFMSC) and pulp tissues (hDPMSC) and shown to express prototypical stem cell markers. The follicle and pulp dental MSCs capacity to differentiate into osteoblast lineage was evaluated after seeding on 3D porous scaffolds of collagen-nanohydroxyapatite/phosphoserine biocomposite cryogel with osteogenic factors in the culture medium. Both tooth-derived MSCs were able to show high ALP activity, express osteogenic gene markers and secrete osteopontin (OPN). Thereafter, designed multicompartment holder adaptable to spinner flasks was used for dynamic culture (50 rpm) of both dental MSCs types within the porous 3D scaffolds. Standard static culture conditions were used as control. Culture under dynamic conditions promoted follicle MSCs proliferation, while improving their spatial distribution within the scaffold. Under dynamic conditions, the biocomposite scaffold promoted MSCs osteogenic differentiation, as suggested by increased alkaline phosphatase (ALP) activity, higher osteogenic gene expression and OPN deposition. In a similar manner, under dynamic conditions, dental pulp MSCs also showed higher ALP activity and proliferation rate, but lower amounts of osteopontin secretion, when compared to static conditions. After implantation, dental follicle MSCs-loaded 3D scaffolds cultured under dynamic conditions showed higher tissue ingrowth and osteogenic differentiation (higher human OPN secretion) than dental pulp cells. Overall, this study explored the use of tooth-derived stem cells as a clinical alternative source for bone tissue engineering, together with an innovative device for dynamic culture of cell-laden 3D scaffolds. Results showed that human MSCs response upon culture on 3D scaffolds, depends on the cells source and the culture regimen. This suggests that both the type of cells and their culture conditions should be carefully adjusted according to the final clinical application.

Silk Fibroin/Collagen/Chitosan Scaffolds Cross-Linked by a Glyoxal Solution as Biomaterials toward Bone Tissue Regeneration.

In this study, three-dimensional materials based on blends of silk fibroin (SF), collagen (Coll), and chitosan (CTS) cross-linked by glyoxal solution were prepared and the properties of the new materials were studied. The structure of the composites and the interactions between scaffold components were studied using FTIR spectroscopy. The microstructure was observed using a scanning electron microscope. The following properties of the materials were measured: density and porosity, moisture content, and swelling degree. Mechanical properties of the 3D materials under compression were studied. Additionally, the metabolic activity of MG-63 osteoblast-like cells on materials was examined. It was found that the materials were characterized by a high swelling degree (up to 3000% after 1 h of immersion) and good porosity (in the range of 80-90%), which can be suitable for tissue engineering applications. None of the materials showed cytotoxicity toward MG-63 cells.

Jet Cutting Technique for the Production of Chitosan Aerogel Microparticles Loaded with Vancomycin.

Biopolymer-based aerogels can be obtained by supercritical drying of wet gels and endowed with outstanding properties for biomedical applications. Namely, polysaccharide-based aerogels in the form of microparticles are of special interest for wound treatment and can also be loaded with bioactive agents to improve the healing process. However, the production of the precursor gel may be limited by the viscosity of the polysaccharide initial solution. The jet cutting technique is regarded as a suitable processing technique to overcome this problem. In this work, the technological combination of jet cutting and supercritical drying of gels was assessed to produce chitosan aerogel microparticles loaded with vancomycin HCl (antimicrobial agent) for wound healing purposes. The resulting aerogel formulation was evaluated in terms of morphology, textural properties, drug loading, and release profile. Aerogels were also tested for wound application in terms of exudate sorption capacity, antimicrobial activity, hemocompatibility, and cytocompatibility. Overall, the microparticles had excellent textural properties, absorbed high amounts of exudate, and controlled the release of vancomycin HCl, providing sustained antimicrobial activity.