Immobilization of alkaline phosphatase on microporous nanofibrous fibrin scaffolds for bone tissue engineering

Kneadable dough-type hydrogel transforming from dynamic to rigid network to repair irregular bone defects

Irregular bone defects, characterized by unpredictable size, shape, and depth, pose a major challenge to clinical treatment. Although various bone grafts are available, none can fully meet the repair needs of the defective area. Here, this study fabricates a dough-type hydrogel (DR-Net), in which the first dynamic network is generated by coordination between thiol groups and silver ions, thereby possessing kneadability to adapt to various irregular bone defects. The second rigid covalent network is formed through photocrosslinking, maintaining the osteogenic space under external forces and achieving a better match with the bone regeneration process. In vitro, an irregular alveolar bone defect is established in the fresh porcine mandible, and the dough-type hydrogel exhibits outstanding shape adaptability, perfectly matching the morphology of the bone defect. After photocuring, the storage modulus of the hydrogel increases 8.6 times, from 3.7 kPa (before irradiation) to 32 kPa (after irradiation). Furthermore, this hydrogel enables effective loading of P24 peptide, which potently accelerates bone repair in Sprague-Dawley (SD) rats with critical calvarial defects. Overall, the dough-type hydrogel with kneadability, space-maintaining capability, and osteogenic activity exhibits exceptional potential for clinical translation in treating irregular bone defects.

Cellulose nano-dispersions enhanced by ultrasound assisted chemical modification drive osteoblast proliferation and differentiation in PVA/HA bone tissue engineering scaffolds

To develop a biological bone tissue scaffold with uniform pore size and good cell adhesion was both challenging and imperative. We prepared modified cellulose nanocrystals (CNCs) dispersants (K-PCNCs) by ultrasound-assisted alkylation modification. Subsequently, nano-hydroxyapatite (HC-K) was synthesized using K-PCNCs as a dispersant and composited with polyvinyl alcohol (PVA) to prepare the scaffold using the ice template method. The results showed that the water contact angle and degree of substitution (135°, 1.53) of the K-PCNCs were highest when the ultrasound power was 450 W and the time was 2 h. The dispersion of K-PCNCs prepared under this condition was optimal. SEM showed that the pore distribution of the composite scaffolds was more homogeneous than the PVA scaffold. The porosity, equilibrium swelling rate, and mechanical properties of the composite scaffolds increased and then decreased with the increase of HC-K content, and reached the maximum values (56.1 %, 807.7 %, and 0.085 ± 0.004 MPa) at 9 % (w/w) of HC-K content. Cell experiments confirmed scaffold has good cytocompatibility and mineralization capacity. The ALP activity reached 1.71 ± 0.25 (ALP activity/mg protein). In conclusion, the scaffolds we developed have good biocompatibility and mechanical properties and have great potential in promoting bone defect repair.

Janus Membrane with Intrafibrillarly Strontium-Apatite-Mineralized Collagen for Guided Bone Regeneration

Commercial collagen membranes face difficulty in guided bone regeneration (GBR) due to the absence of hierarchical structural design, effective interface management, and diverse bioactivity. Herein, a Janus membrane called SrJM is developed that consists of a porous collagen face to enhance osteogenic function and a dense face to maintain barrier function. Specifically, biomimetic intrafibrillar mineralization of collagen with strontium apatite is realized by liquid precursors of amorphous strontium phosphate. Polycaprolactone methacryloyl is further integrated on one side of the collagen as a dense face, which endows SrJM with mechanical support and a prolonged lifespan. In vitro experiments demonstrate that the dense face of SrJM acts as a strong barrier against fibroblasts, while the porous face significantly promotes cell adhesion and osteogenic differentiation through activation of calcium-sensitive receptor/integrin/Wnt signaling pathways. Meanwhile, SrJM effectively enhances osteogenesis and angiogenesis by recruiting stem cells and modulating osteoimmune response, thus creating an ideal microenvironment for bone regeneration. In vivo studies verify that the bone defect region guided by SrJM is completely repaired by newly formed vascularized bone. Overall, the outstanding performance of SrJM supports its ongoing development as a multifunctional GBR membrane, and this study provides a versatile strategy of fabricating collagen-based biomaterials for hard tissue regeneration.

Nano-hydroxyapatite structures for bone regenerative medicine: Cell-material interaction

Bone tissue engineering holds great promise for the regeneration of damaged or severe bone defects. However, several challenges hinder its translation into clinical practice. To address these challenges, interdisciplinary efforts and advances in biomaterials, cell biology, and bioengineering are required. In recent years, nano-hydroxyapatite (nHA)-based scaffolds have emerged as a promising approach for the development of bone regenerative agents. The unique similarity of nHA with minerals found in natural bones promotes remineralization and stimulates bone growth, which are crucial factors for efficient bone regeneration. Moreover, nHA exhibits desirable properties, such as strong chemical interactions with bone and facilitation of tissue growth, without inducing inflammation or toxicity. It also promotes osteoblast survival, adhesion, and proliferation, as well as increasing alkaline phosphatase activity, osteogenic differentiation, and bone-specific gene expression. However, it is important to note that the effect of nHA on osteoblast behavior is dose-dependent, with cytotoxic effects observed at higher doses. Additionally, the particle size of nHA plays a crucial role, with smaller particles having a more significant impact. Therefore, in this review, we highlighted the potential of nHA for improving bone regeneration processes and summarized the available data on bone cell response to nHA-based scaffolds. In addition, an attempt is made to portray the current status of bone tissue engineering using nHA/polymer hybrids and some recent scientific research in the field.

Entropically Toughened Robust Biodegradable Polymer Blends and Composites for Bone Tissue Engineering

Biodegradable polymers and composites are promising candidates for biomedical implants in tissue engineering. However, state-of-the-art composite scaffolds suffer from a strength-toughness dilemma due to poor interfacial adhesion and filler dispersion. In this work, we propose a facile and scalable strategy to fabricate strong and tough biocomposite scaffolds through interfacial toughening. The immiscible biopolymer matrix is compatible by the direct incorporation of a third polymer. Densely entangled polymer chains lead to massive crazes and global shear yields under tension. Weak chemical interaction and high-shear melt processing create nanoscale dispersion of nanofillers within the matrix. The resultant ternary blends and composites exhibit an 11-fold increase in toughness without compromising stiffness and strength. At 70% porosity, three-dimensional (3D)-printed composite scaffolds demonstrate high compressive properties comparable to those of cancellous bones. In vitro cell culture on the scaffolds demonstrates not only good cell viability but also effective osteogenic differentiation of human mesenchymal stem cells. Our findings present a widely applicable strategy to develop high-performance biocomposite materials for tissue regeneration.

Effects of using collagen and aloe vera grafted fibroin scaffolds on osteogenic differentiation of rat bone marrow mesenchymal stem cells in SBF-enriched cell culture medium

In the study, collagen and aloe vera were grafted onto silk fibroin with two different methods, and 3D-microporous scaffolds (1F5C4A1 and 2F5C4A1) were formed by lyophilization. Three osteogenic cultures were started by seeding rat bone marrow mesenchymal stem cells (MSCs) and pre-induced MSC (osteoblast (OB)) on biopolymeric scaffolds. The osteogenic medium was enriched with 10% (v/v) simulated body fluid (SBF) to promote mineralization and osteogenic differentiation in one of the MSC cultures and the OB culture. X-ray diffraction (XRD), scanning electron microscopy (SEM), scanning electron microscopy- energy dispersive spectrum (SEM-EDS) analyses on cellular samples and histochemical (alizarin red, safranin-O, alcian blue) and immunohistochemical (anti-collagen-1, anti-osteocalcin, anti-osteopontin) staining showed that bone-like mineralization was occurred by both chemically and cellular activity. In addition, pre-osteogenic induction of MSCs in 2D-cultured was found to promote osteogenesis more rapidly when started 3D-cultured. These results indicated that enrichment of the cell culture medium with SBF is sufficient forin vitromineralization rather than using high concentrations of SBF. The findings showed that OB cells on the 2F5C4A1 scaffold obtained the best osteogenic activity. Still, other culture media with 10% SBF content could be used for bone tissue engineering under osteogenic induction.

Combination adipose-derived mesenchymal stem cells-demineralized dentin matrix increase bone marker expression in periodontitis rats

Background

Periodontal disease is common in both developed and developing countries and affects around 20-50% of the global population, especially in adolescents, adults and the elderly is a public health problem. ADMSCs have the advantage of regenerating damaged tissue with high quality. DDM in the form of slices can improve healing in the mandibular sockets of molar teeth. The combination of ADMSC-DDM is expected to accelerate bone regeneration.

Objectives

To analyze the combination of ADMSCs-DDM at increasing bone marker expression in periodontitis rats.

Methods

This research is experimental with a randomized control group post-test-only design. A total of 50 male Wistar rats were divided into four groups: 1) normal group (K); 2) CP model (K + ); 3) CP model and treated with DDM scaffold therapy (K(s)); 4) CP model and treated with ADMSCs-DDM combination therapy (K(sc)). Making a CP model with injected LPS P. gingivalis into interproximal gingiva of the right first and second lower molars. The in vivo research stage was the implantation of the DDM scaffold and the ADMSCs-DDM combination in the rat periodontal pocket. Rats were euthanized on days 7, 14, and 28, and immunohistochemistry of STRO-1, RUNX-2, OSX, COL-I, and OCN was performed. DDM scaffolds are made in 10%, 50% and 100% concentrations for MTT testing. Statistical results were analyzed with Kruskal-Wallis and Mann-Whitney tests.

Results

The results of the MTT scaffold DDM were significant in the 10%, 50%, and 100% dilution groups (p < 0.05). The results showed there was a substantial difference in the expression of STRO-1 between the study groups (p < 0.05). The (K(sc)) was significantly higher than the (K) in RUNX-2 expression (p < 0.05). OSX expression showed significant results between study groups (p < 0.05). The expression of OCN and COL-I showed a significant difference in all study groups on day 28, where the (K(sc)) was higher than the (K) (p < 0.05).

Conclusions

Administration of the ADMSCs-DDM combination can accelerate alveolar bone regeneration on day 28. There is a mechanism of alveolar bone regeneration through the STRO-1, RUNX-2, OSX, and the COL-I pathway in periodontitis models.

Modified-Hydroxyapatite-Chitosan Hybrid Composite Interfacial Coating on 3D Polymeric Scaffolds for Bone Tissue Engineering

Three dimensional (3D) scaffolds have huge limitations due to their low porosity, mechanical strength, and lack of direct cell-bioactive drug contact. Whereas bisphosphonate drug has the ability to stimulate osteogenesis in osteoblasts and bone marrow mesenchymal stem cells (hMSC) which attracted its therapeutic use. However it is hard administration low bioavailability, and lack of site-specificity, limiting its usage. The proposed scaffold architecture allows cells to access the bioactive surface at their apex by interacting at the scaffold's interfacial layer. The interface of 3D polycaprolactone (PCL) scaffolds has been coated with alendronate-modified hydroxyapatite (MALD) enclosed in a chitosan matrix, to mimic the native environment and stupulate the through interaction of cells to bioactive layer. Where the mechanical strength will be provided by the skeleton of PCL. In the MALD composite's hydroxyapatite (HAP) component will govern alendronate (ALD) release behavior, and HAP presence will drive the increase in local calcium ion concentration increases hMSC proliferation and differentiation. In results, MALD show release of 86.28 ± 0.22. XPS and SEM investigation of the scaffold structure, shows inspiring particle deposition with chitosan over the interface. All scaffolds enhanced cell adhesion, proliferation, and osteocyte differentiation for over a week without in vitro cell toxicity with 3.03 ± 0.2 kPa mechanical strength.

Performance optimization of biomimetic ant-nest silver nanoparticle coatings for antibacterial and osseointegration of implant surfaces

Infection prevention and bone-implant integration remain major clinical challenges. Silver nanoparticle (AgNPs) bone-implant coatings have received extensive attention. Balancing the toxicity and antibacterial properties of AgNP coatings has become a significant problem. In this study, inspired by the structure of the ant-nest, a polyetherimide (PEI) coating with ant-nest structure was prepared, aiming to realize the structural modification of the AgNPs coating. AgNPs were loaded in the inner porous area of the PEI ant-nest coating, avoiding direct contact between AgNPs and cells. The nanopores on the surface of the coating ensured the orderly release of silver ions. SEM, FTIR, XPS, and XRD experiments confirmed that the PEI ant-nest coating was successfully prepared. Interestingly, in the PEI ant-nest coating, Ag⁺ showed a steady increase in the release trend within 28 days, and there was no early burst release phenomenon. In -vivo experiments showed a good control effect for local infection. In order to improve the osteogenic properties of the materials, 45S5 bioactive glasses (BG) were loaded to achieve further osseointegration. In general, this natural ant-nest-inspired surface modification coating for orthopedic prostheses provides a new strategy for balancing the antibacterial and toxic effects of AgNP coatings.

Biomimetic natural biomaterials for tissue engineering and regenerative medicine: new biosynthesis methods, recent advances, and emerging applications

Biomimetic materials have emerged as attractive and competitive alternatives for tissue engineering (TE) and regenerative medicine. In contrast to conventional biomaterials or synthetic materials, biomimetic scaffolds based on natural biomaterial can offer cells a broad spectrum of biochemical and biophysical cues that mimic the in vivo extracellular matrix (ECM). Additionally, such materials have mechanical adaptability, microstructure interconnectivity, and inherent bioactivity, making them ideal for the design of living implants for specific applications in TE and regenerative medicine. This paper provides an overview for recent progress of biomimetic natural biomaterials (BNBMs), including advances in their preparation, functionality, potential applications and future challenges. We highlight recent advances in the fabrication of BNBMs and outline general strategies for functionalizing and tailoring the BNBMs with various biological and physicochemical characteristics of native ECM. Moreover, we offer an overview of recent key advances in the functionalization and applications of versatile BNBMs for TE applications. Finally, we conclude by offering our perspective on open challenges and future developments in this rapidly-evolving field.

Cooperative Calcium Phosphate Deposition on Collagen-Inspired Short Peptide Nanofibers for Application in Bone Tissue Engineering

In recent years, immense attention has been devoted over the production of osteoinductive materials. To this direction, collagen has a dominant role in developing hard tissues and plays a crucial role in the biomineralization of these tissues. Here, we demonstrated for the first time the potential of the shortest molecular pentapeptide domain inspired from collagen toward mineralizing hydroxyapatite on peptide fibers to develop bone-filling material. Our simplistic approach adapted the easy and facile route of introducing the metal ions onto the peptide nanofibers, displaying adsorbed glutamate onto the surface. This negatively charged surface further induces the nucleation of the crystalline growth of hydroxyapatite. Interestingly, nucleation and growth of the hydroxyapatite crystals lead to the formation of a self-supporting hydrogel to construct a suitable interface for cellular interactions. Furthermore, microscopic and spectroscopic investigations revealed the crystalline growth of the hydroxyapatite onto peptide fibers. The physical properties were also influenced by this crystalline deposition, as evident from the hierarchical organization leading to hydrogels with enhanced mechanical stiffness and improved thermal stability of the scaffold. Furthermore, the mineralized peptide fibers were highly compatible with osteoblast cells and showed increased cellular biomarkers production, which further reinforced the potential application toward effectively fabricating the grafts for bone tissue engineering.

A novel injectable hydrogel containing polyetheretherketone for bone regeneration in the craniofacial region

Polyetheretherketone (PEEK) is an organic material introduced as an alternative for titanium implants. Injectable hydrogels are the most promising approach for bone regeneration in the oral cavity to fill the defects with irregular shapes and contours conservatively. In the current study, injectable Aldehyde-cellulose nanocrystalline/silk fibroin (ADCNCs/SF) hydrogels containing PEEK were synthesized, and their bone regeneration capacity was evaluated. Structure, intermolecular interaction, and the reaction between the components were assessed in hydrogel structure. The cytocompatibility of the fabricated scaffolds was evaluated on human dental pulp stem cells (hDPSCs). Moreover, the osteoinduction capacity of ADCNCs/SF/PEEK hydrogels on hDPSCs was evaluated using Real-time PCR, Western blot, Alizarin red staining and ALP activity. Bone formation in critical-size defects in rats' cranial was assessed histologically and radiographically. The results confirmed the successful fabrication of the hydrogel and its osteogenic induction ability on hDPSCs. Furthermore, in in vivo phase, bone formation was significantly higher in ADCNCs/SF/PEEK group. Hence, the enhanced bone regeneration in response to PEEK-loaded hydrogels suggested its potential for regenerating bone loss in the craniofacial region, explicitly surrounding the dental implants.

A Doubly Fmoc-Protected Aspartic Acid Self-Assembles into Hydrogels Suitable for Bone Tissue Engineering

Hydrogels have been used as scaffolds for biomineralization in tissue engineering and regenerative medicine for the repair and treatment of many tissue types. In the present work, we studied an amino acid-based material that is attached to protecting groups and self-assembles into biocompatible and stable nanostructures that are suitable for tissue engineering applications. Specifically, the doubly protected aspartic residue (Asp) with fluorenyl methoxycarbonyl (Fmoc) protecting groups have been shown to lead to the formation of well-ordered fibrous structures. Many amino acids and small peptides which are modified with protecting groups display relatively fast self-assembly and exhibit remarkable physicochemical properties leading to three-dimensional (3D) networks, the trapping of solvent molecules, and forming hydrogels. In this study, the self-assembling fibrous structures are targeted toward calcium binding and act as nucleation points for the binding of the available phosphate groups. The cell viability, proliferation, and osteogenic differentiation of pre-osteoblastic cells cultured on the formed hydrogel under various conditions demonstrate that hydrogel formation in CaCl₂ and CaCl₂-Na₂HPO₄ solutions lead to calcium ion binding onto the hydrogels and enrichment with phosphate groups, respectively, rendering these mechanically stable hydrogels osteoinductive scaffolds for bone tissue engineering.

Mineralized Enzyme-Based Biomaterials with Superior Bioactivities for Bone Regeneration

The formation and metabolic balance of bone tissue is a controllable process of biomineralization, which is regulated by various cells, biomolecules, and ions. Enzyme molecules play an important role in this process, and alkaline phosphatase (ALP) is one of the most critical factors. In this study, inspired by the process of bone biomineralization, a biomimetic strategy is achieved for the preparation of mineralized ALP nanoparticles (MALPNs), by taking advantages of the unique reaction between ALP and calcium ions in Dulbecco's modified Eagle's medium. Benefiting from the mild biomineralization reaction, the MALPN system highly maintains the activity of ALP. Furthermore, the in vitro studies show that the MALPN system significantly enhances the proliferation of bone marrow mesenchymal stem cells and upregulates their osteogenic differentiation. When evaluated as synthetic graft materials for bone regeneration, the MALPN-incorporated gelatin methacryloyl graft shows excellent mechanical properties, a sustained release profile of ALP, and high biocompatibility and efficacy in guiding bone regeneration and vascularization for critical-sized rat calvarial defect. Moreover, we also demonstrate that the biomimetic mineralization strategy can be adopted for other proteins such as acid phosphatase, bovine serum albumin, fibrinogen, and gelatin, suggesting its universality for constructing mineralized protein-/enzyme-based bioactive materials for the application of tissue regeneration.

Cytocompatibility and bioactive potential of AH Plus Bioceramic Sealer: an in vitro study

Aim

To assess the cytocompatibility and bioactive potential of the new calcium silicate cement‐based sealer AH Plus Bioceramic Sealer (AHPbcs) on human periodontal ligament stem cells (hPDLSCs) compared with the epoxy resin‐based sealer AH Plus (AHP) and the calcium silicate cement‐based sealer Endosequence BC Sealer (ESbcs).

Methodology

Standardized sample discs and 1:1, 1:2 and 1:4 eluates of the tested materials were prepared. The following assays were performed: surface element distribution via SEM–EDX, cell attachment and morphology via SEM, cell viability via a MTT assay, cell migration/proliferation via a wound‐healing assay, osteo/cemento/odontogenic marker expression via RT‐qPCR and cell mineralized nodule formation via Alizarin Red S staining. HPDLSCs were isolated from extracted third molars. Comparisons were made with hPDLSCs cultured in unconditioned (negative control) or osteogenic (positive control) culture media. Statistical significance was established at p < .05.

Results

A higher peak of Ca²+ was detected from ESbcs compared with AHPbcs and AHP in SEM–EDX. Both AHPbcs and ESbcs showed significantly positive results in the cytocompatibility assays (cell viability, migration/proliferation, attachment and morphology) compared with a negative control group, whilst AHP showed significant negative results. Both AHPbcs and ESbcs exhibited an upregulation of at least one osteo/odonto/cementogenic marker compared with the negative and positive control groups. Both ESbcs and AHPbcs showed a significantly higher calcified nodule formation than the negative and positive control groups, indicative of their biomineralization potential and were also significantly higher than AHP group.

Conclusion

AH Plus Bioceramic Sealer exhibited a significantly higher cytocompatibility and bioactive potential than AH Plus and a similar cytocompatibility to that of Endosequence BC Sealer. Endosequence BC Sealer exhibited a significantly higher mineralization potential than the other tested sealers. The results from this in vitro study act as supporting evidence for the use of AH Plus Bioceramic Sealer in root canal treatment.

3D bioprinted poly(lactic acid)/mesoporous bioactive glass based biomimetic scaffold with rapid apatite crystallization and in-vitro Cytocompatability for bone tissue engineering

In the recent years, bone tissue engineering is regarded as the promising solution for treatment of bone defects which arises due to trauma, infection and surgical intervention. In view of this, several polymer or ceramic based constructs are envisaged for bone tissue engineering potential. However, scaffolds based on pure polymeric materials suffer from slow bioactivity characteristics. On the other hand, scaffolds based on ceramic materials do not offer sufficient strength for load bearing applications. In order to overcome these drawbacks, the current work aims to develop mixed matrix scaffolds based on poly (L-lactic acid)/mesoporous bioactive glass composite with the formulation of 30:70 weight ratio, which mimics the natural bone composition. In the current work, PLA/MBG (30:70) composite based bioink suitable for 3D bioprinting is indigenously developed and its rheological characteristics are evaluated. The 3D architecture for PLA/MBG composite scaffold is designed using Solidworks CAD 2015 and the scaffolds are fabricated using pneumatic based 3D bioprinting technology, which has not been documented earlier for this formulation in view of bone tissue engineering to the best of our knowledge. Followed by this, optimization of printing parameters in order to develop 3D PLA/MBG composite constructs with hierarchical pore architecture suitable for bone tissue engineering is performed. The SEM analysis confirmed that the pore size of the 3D printed PLA/MBG composite scaffolds falls in the range of 500-700 μm, which corresponds to the macroporous nature of the scaffolds useful for bone cell growth. The mechanical analysis confirmed the superior compressive modulus and yield strength for PLA/MBG composite scaffold in comparison to neat PLA. The in-vitro bioactivity assessment showed rapid apatite crystallization by attaining Ca/P ratio of 1.66 equivalent to natural bone mineral within 3rd day of SBF treatment for PLA/MBG composite scaffold, thus indicating the excellent bioactivity behaviour. The 3D bioprinted PLA/MBG composite scaffold showed promising response in terms of cell attachment and proliferation, mineralization as well as gene expression characteristics while assessed through of in-vitro biological assessment using MG-63 osteosarcoma cells. In this regard, the 3D bioprinted PLA/MBG scaffold could be applied as potential implant for bone tissue engineering application.

Nanoarchitectonics of Fullerene Based Enzyme Mimics for Osteogenic Induction of Stem Cells

Enzyme mimicry is a topic of considerable interest in the development of multifunctional biomimetic materials. Mimicking enzyme activity is a major challenge in biomaterials research, and artificial analogs that simultaneously recapitulate the catalytic and metabolic activity of native enzymes are considered to be the ultimate goal of this field. This consensus may be challenged by self-assembling multifunctional nanostructures to develop close-to-fidelity enzyme mimics. Here, we present the ability of fullerene nanostructures decorated with active units to form enzyme-like materials that can mimic phosphatases in a metal-free manner. These nanostructures self-assemble into nanoclusters forming multiple random active sites that can cleave both phosphomonoesters and phosphodiesters while being more specific for the phosphomonoesters. Moreover, they are reusable and show an increase in catalytic activity over multiple cycles similar to their natural counterparts. In addition to having enzyme-like catalytic properties, these nanocatalysts imitate the biological functions of their natural analogs by inducing biomineralization and osteoinduction in preosteoblast and mesenchymal stem cells in vitro studies. This article is protected by copyright. All rights reserved.

Alkaline Phosphatase Activity of Serum Affects Osteogenic Differentiation Cultures

Fetal bovine serum (FBS) is a widely used supplement in cell culture medium, despite its known variability in composition, which greatly affects cellular function and consequently the outcome of studies. In bone tissue engineering, the deposited mineralized matrix is one of the main outcome parameters, but using different brands of FBS can result in large variations. Alkaline phosphatase (ALP) is present in FBS. Not only is ALP used to judge the osteogenic differentiation of bone cells, it may affect deposition of mineralized matrix. The present study focused on the enzymatic activity of ALP in FBS of different suppliers and its contribution to mineralization in osteogenic differentiation cultures. It was hypothesized that culturing cells in a medium with high intrinsic ALP activity of FBS will lead to higher mineral deposition compared to media with lower ALP activity. The used FBS types were shown to have significant differences in enzymatic ALP activity. Our results indicate that the ALP activity of the medium not only affected the deposited mineralized matrix but also the osteogenic differentiation of cells as measured by a changed cellular ALP activity of human-bone-marrow-derived mesenchymal stromal cells (hBMSCs). In media with low inherent ALP activity, the cellular ALP activity was increased and played the major role in the mineralization process, while in media with high intrinsic ALP activity contribution from the serum, less cellular ALP activity was measured, and the ALP activity of the medium also contributed to mineral formation substantially. Our results highlight the diverse effects of ALP activity intrinsic to FBS on osteogenic differentiation and matrix mineralization and how FBS can determine the experimental outcomes, in particular for studies investigating matrix mineralization. Once again, the need to replace FBS with more controlled and known additives is highlighted.

Effectiveness of bio-dispersant in homogenizing hydroxyapatite for proliferation and differentiation of osteoblast

Hydroxyapatite (HA), an inorganic compound, plays an essential role in the proliferation and differentiation of bone cells. Using cellulose nanocrystals (CNCs) as green dispersants to improve homogenization of HA is promising in the fabrication of nanocomposite scaffolds with biocompatibility for bone tissue engineering. The HA/CNC (HC) nanoparticle suspension was incorporated in polyvinyl alcohol (PVA)-based scaffold to investigate the physical and chemical properties. The PVA/HC composites demonstrated high porous structure and swelling ability for cell attachment and a 3-fold improvement in compressive modulus compared with free HC scaffold. Moreover, the presence of HC nanoparticles has promoted the proliferation and mineralization of pre-osteoblast. Our findings could provide an effective strategy by using bio-dispersants to incorporate mineral elements into synthetic polymers for the fabrication of functional tissue engineering scaffolds.

Biohybrid Variable-Stiffness Soft Actuators that Self-Create Bone

Inspired by the dynamic process of initial bone development, in which a soft tissue turns into a solid load-bearing structure, the fabrication, optimization, and characterization of bioinduced variable-stiffness actuators that can morph in various shapes and change their properties from soft to rigid are hereby presented. Bilayer devices are prepared by combining the electromechanically active properties of polypyrrole with the compliant behavior of alginate gels that are uniquely functionalized with cell-derived plasma membrane nanofragments (PMNFs), previously shown to mineralize within 2 days, which promotes the mineralization in the gel layer to achieve the soft to stiff change by growing their own bone. The mineralized actuator shows an evident frozen state compared to the movement before mineralization. Next, patterned devices show programmed directional and fixated morphing. These variable-stiffness devices can wrap around and, after the PMNF-induced mineralization in and on the gel layer, adhere and integrate onto bone tissue. The developed biohybrid variable-stiffness actuators can be used in soft (micro-)robotics and as potential tools for bone repair or bone tissue engineering.

Enhanced p53 Levels Are Involved in the Reduced Mineralization Capacity of Osteoblasts Derived from Shwachman-Diamond Syndrome Subjects

Shwachman-Diamond syndrome (SDS) is a rare autosomal recessive disorder characterized by bone marrow failure, exocrine pancreatic insufficiency, and skeletal abnormalities, caused by loss-of-function mutations in the SBDS gene, a factor involved in ribosome biogenesis. By analyzing osteoblasts from SDS patients (SDS-OBs), we show that SDS-OBs displayed reduced SBDS gene expression and reduced/undetectable SBDS protein compared to osteoblasts from healthy subjects (H-OBs). SDS-OBs cultured in an osteogenic medium displayed a lower mineralization capacity compared to H-OBs. Whole transcriptome analysis showed significant differences in the gene expression of SDS-OBs vs. H-OBs, particularly in the ossification pathway. SDS-OBs expressed lower levels of the main genes responsible for osteoblastogenesis. Of all downregulated genes, Western blot analyses confirmed lower levels of alkaline phosphatase and collagen type I in SDS-OBs than in H-OBs. Interestingly, SDS-OBs showed higher protein levels of p53, an inhibitor of osteogenesis, compared to H-OBs. Silencing of Tp53 was associated with higher collagen type I and alkaline phosphatase protein levels and an increase in SDS-OB mineralization capacity. In conclusion, our results show that the reduced capacity of SDS-OBs to mineralize is mediated, at least in part, by the high levels of p53 and highlight an important role of SBDS in osteoblast functions.

Zastosowanie fibryny w inżynierii tkankowej. Osiągnięcia i perspektywy

W ostatnich latach istotnym obszarem zastosowania fibryny stała się inżynieria tkankowa, w której wykorzystuje się naturalne właściwości biostatyczne i bioaktywne fibryny, a także możliwość pułapkowania i wiązania w jej strukturze czynników wzrostu. Fibryna jest najczęściej stosowana w postaci żeli i dysków. Jednak każda postać wskutek pochłaniania wody docelowo przyjmuje postać żelu. Białko to w warunkach in vivo spełnia rolę rusztowania dla komórek, a także może być aplikowane w miejsca trudno dostępne – może wypełniać ubytki tkanek i podtrzymywać tkanki okalające, zapobiegając ich zapadaniu się. Ponadto fibryna hamuje krwawienie i inicjuje proces odnowy, jak również pełni rolę stymulatora wzrostu komórek. Przez modyfikacje struktury fibryny cząsteczkami adhezyjnymi, można przyspieszyć odbudowę prawidłowej struktury tkanek. Jej właściwości strukturalne mogą być także wykorzystywane jako rezerwuar czynników wzrostu i system ich przedłużonego uwalniania. Fibryna jest materiałem biodegradowalnym, umożliwiając skorelowanie ubytku matrycy fibrynowej z odbudową tkanek własnych pacjenta. Wprowadzenie metod druku 3D i elektroprzędzenia umożliwia formulację dopasowanych do uszkodzeń kształtek oraz włóknin bez utraty bioaktywnych funkcji fibryny. Metody te umożliwiają także poprawę właściwości mechanicznych przez otrzymywanie m.in. włóknin fibryny z innymi polimerami, co jest szczególnie uzasadnione w przypadku materiałów stosowanych w odbudowie takich struktur jak ścięgna czy kości. Biotechnologiczna synteza fibrynogenu może w przyszłości uniezależnić pozyskiwanie go z krwi i zwiększyć popularność wyrobów medycznych otrzymywanych z fibryny.

Bioprinting of Stem Cells in Multimaterial Scaffolds and Their Applications in Bone Tissue Engineering

Bioprinting stem cells into three-dimensional (3D) scaffolds has emerged as a new avenue for regenerative medicine, bone tissue engineering, and biosensor manufacturing in recent years. Mesenchymal stem cells, such as adipose-derived and bone-marrow-derived stem cells, are capable of multipotent differentiation in a 3D culture. The use of different printing methods results in varying effects on the bioprinted stem cells with the appearance of no general adverse effects. Specifically, extrusion, inkjet, and laser-assisted bioprinting are three methods that impact stem cell viability, proliferation, and differentiation potential. Each printing method confers advantages and disadvantages that directly influence cellular behavior. Additionally, the acquisition of 3D bioprinters has become more prominent with innovative technology and affordability. With accessible technology, custom 3D bioprinters with capabilities to print high-performance bioinks are used for biosensor fabrication. Such 3D printed biosensors are used to control conductivity and electrical transmission in physiological environments. Once printed, the scaffolds containing the aforementioned stem cells have a significant impact on cellular behavior and differentiation. Natural polymer hydrogels and natural composites can impact osteogenic differentiation with some inducing chondrogenesis. Further studies have shown enhanced osteogenesis using cell-laden scaffolds in vivo. Furthermore, selective use of biomaterials can directly influence cell fate and the quantity of osteogenesis. This review evaluates the impact of extrusion, inkjet, and laser-assisted bioprinting on adipose-derived and bone-marrow-derived stem cells along with the effect of incorporating these stem cells into natural and composite biomaterials.

Enzyme-polymeric/inorganic metal oxide/hybrid nanoparticle bio-conjugates in the development of therapeutic and biosensing platforms

Background

Because enzymes can control several metabolic pathways and regulate the production of free radicals, their simultaneous use with nanoplatforms showing protective and combinational properties is of great interest in the development of therapeutic nano-based platforms. However, enzyme immobilization on nanomaterials is not straightforward due to the toxic and unpredictable properties of nanoparticles in medical practice.

Aim of review

In fact, because of the ability to load enzymes on nano-based supports and increase their renewability, scientific groups have been tempted to create potential therapeutic enzymes in this field. Therefore, this study not only pays attention to the therapeutic and diagnostic applications of diseases by enzyme-nanoparticle (NP) bio-conjugate (abbreviated as: ENB), but also considers the importance of nanoplatforms used based on their toxicity, ease of application and lack of significant adverse effects on loaded enzymes. In the following, based on the published reports, we explained that the immobilization of enzymes on polymers, inorganic metal oxide and hybrid compounds provide hopes for potential use of ENBs in medical activities. Then, the use of ENBs in bioassay activities such as paper-based or wearing biosensors and lab-on-chip/microfluidic biosensors were evaluated. Finally, this review addresses the current challenges and future perspective of ENBs in biomedical applications.

Key scientific concepts of review

This literature may provide useful information regarding the application of ENBs in biosensing and therapeutic platforms.

Bioprocess Optimization for the Production of Arthrospira (Spirulina) platensis Biomass Enriched in the Enzyme Alkaline Phosphatase

The enzyme alkaline phosphatase (ALP) is gaining interest because it exerts bioactive properties and may be a potentially important therapeutic agent for many disorders and diseases. Microalgae are considered an important novel source for the production of diverse bio-compounds and are gaining momentum as functional foods/feeds supplements. So far, studies for the production of ALP are limited to mammalian and partly to some heterotrophic microbial sources after its extraction and/or purification. Methods: Arthrospira was cultivated under P-limitation bioprocess and the effect of the P-limitation degree on the ALP enrichment was studied. The aim of this work was to optimize the cultivation of the edible and generally-recognized-as-safe (GRAS) cyanobacterium Arthrospira platensis for the production of single-cell (SC) biomass enriched in ALP as a potential novel functional diet supplement. Results: The results revealed that the relationship between intracellular-P and single-cell alkaline phosphatase (SC-ALP) activity was inverse; SC-ALP activity was the highest (around 50 U g-1) when intracellular-P was the lowest possible (around 1.7 mg-P g-1) and decreased gradually as P availability increased reaching around 0.5 U g-1 in the control cultures. Under the strongest P-limited conditions, a more than 100-fold increase in SC-ALP activity was obtained; however, protein content of A. platensis decreased significantly (around 22-23% from 58%). Under a moderate P-limitation degree (at intracellular-P of 3.6 mg-P g-1), there was a relatively high SC-ALP activity (>28 U g-1) while simultaneously, a relative high protein content (46%) was attained, which reflects the possibility to produce A. platensis enriched in ALP retaining though its nutritional value as a protein rich biomass source. The paper presents also results on how several parameters of the ALP activity assay, such as pH, temperature etc., and post-harvest treatment (hydrothermal treatment and biomass drying), influence the SC-ALP activity.

Electron Beam-Treated Enzymatically Mineralized Gelatin Hydrogels for Bone Tissue Engineering

Biological hydrogels are highly promising materials for bone tissue engineering (BTE) due to their high biocompatibility and biomimetic characteristics. However, for advanced and customized BTE, precise tools for material stabilization and tuning material properties are desired while optimal mineralisation must be ensured. Therefore, reagent-free crosslinking techniques such as high energy electron beam treatment promise effective material modifications without formation of cytotoxic by-products. In the case of the hydrogel gelatin, electron beam crosslinking further induces thermal stability enabling biomedical application at physiological temperatures. In the case of enzymatic mineralisation, induced by Alkaline Phosphatase (ALP) and mediated by Calcium Glycerophosphate (CaGP), it is necessary to investigate if electron beam treatment before mineralisation has an influence on the enzymatic activity and thus affects the mineralisation process. The presented study investigates electron beam-treated gelatin hydrogels with previously incorporated ALP and successive mineralisation via incubation in a medium containing CaGP. It could be shown that electron beam treatment optimally maintains enzymatic activity of ALP which allows mineralisation. Furthermore, the precise tuning of material properties such as increasing compressive modulus is possible. This study characterizes the mineralised hydrogels in terms of mineral formation and demonstrates the formation of CaP in dependence of ALP concentration and electron dose. Furthermore, investigations of uniaxial compression stability indicate increased compression moduli for mineralised electron beam-treated gelatin hydrogels. In summary, electron beam-treated mineralized gelatin hydrogels reveal good cytocompatibility for MG-63 osteoblast like cells indicating a high potential for BTE applications.

Osteogenic Capability of Vaterite-Coated Nonwoven Polycaprolactone Scaffolds for In Vivo Bone Tissue Regeneration

In current orthopedic practice, bone implants used to-date often exhibit poor osteointegration, impaired osteogenesis, and, eventually, implant failure. Actively pursued strategies for tissue engineering could overcome these shortcomings by developing new hybrid materials with bioinspired structure and enhanced regenerative potential. In this study, the osteogenic and therapeutic potential of bioactive vaterite is investigated as a functional component of a fibrous polymeric scaffold for bone regeneration. Hybrid two-layered polycaprolactone scaffolds coated with vaterite (PCL/CaCO₃ ) are studied during their 28-days implantation period in a rat femur defect. After this period, the study of tissue formation in the defected area is performed by the histological study of femur cross-sections. Immobilization of alkaline phosphatase (ALP) into PCL/CaCO₃ scaffolds accelerates new bone tissue formation and defect repair. PCL/CaCO₃ and PCL/CaCO₃ /ALP scaffolds reveal 37.3% and 62.9% areas, respectively, filled with newly formed bone tissue in cross-sections compared to unmineralized PCL scaffold (17.5%). Bone turnover markers are monitored on the 7th and 28th days after implantation and reveal an increase of osteocalcin level for both PCL/CaCO₃ and PCL/CaCO₃ /ALP compared with PCL indicating the activation of osteogenesis. These findings indicate that vaterite, as an osteoconductive component of polymeric scaffolds, promotes osteogenesis, supports angiogenesis, and facilitates bone defect repair.

Strategies to Use Nanofiber Scaffolds as Enzyme-Based Biocatalysts in Tissue Engineering Applications

Nanofibers are considered versatile materials with remarkable potential in tissue engineering and regeneration. In addition to their extracellular matrix-mimicking properties, nanofibers can be functionalized with specific moieties (e.g., antimicrobial nanoparticles, ceramics, bioactive proteins, etc.) to improve their overall performance. A novel approach in this regard is the use of enzymes immobilized onto nanofibers to impart biocatalytic activity. These nanofibers are capable of carrying out the catalysis of various biological processes that are essential in the healing process of tissue. In this review, we emphasize the use of biocatalytic nanofibers in various tissue regeneration applications. Biocatalytic nanofibers can be used for wound edge or scar matrix digestion, which reduces the hindrance for cell migration and proliferation, hence displaying applications in fast tissue repair, e.g., spinal cord injury. These nanofibers have potential applications in bone regeneration, mediating osteogenic differentiation, biomineralization, and matrix formation through direct enzyme activity. Moreover, enzymes can be used to undertake efficient crosslinking and fabrication of nanofibers with better physicochemical properties and tissue regeneration potential.

Delivery of Alkaline Phosphatase Promotes Periodontal Regeneration in Mice

Factors regulating the ratio of pyrophosphate (PP_i) to phosphate (P_i) modulate biomineralization. Tissue-nonspecific alkaline phosphatase (TNAP) is a key promineralization enzyme that hydrolyzes the potent mineralization inhibitor PP_i. The goal of this study was to determine whether TNAP could promote periodontal regeneration in bone sialoprotein knockout mice (Ibsp^-/- mice), which are known to have a periodontal disease phenotype. Delivery of TNAP was accomplished either systemically (through a lentiviral construct expressing a mineral-targeted TNAP-D₁₀ protein) or locally (through addition of recombinant human TNAP to a fenestration defect model). Systemic TNAP-D₁₀ delivered by intramuscular injection at 5 d postnatal (dpn) increased circulating alkaline phosphatase (ALP) levels in Ibsp^-/- mice by 5-fold at 30 dpn, with levels returning to normal by 60 dpn when tissues were evaluated by micro-computed tomography and histology. Local delivery of recombinant human TNAP to fenestration defects in 5-wk-old wild type (WT) and Ibsp^-/- mice did not alter long-term circulating ALP levels, and tissues were evaluated by micro-computed tomography and histology at postoperative day 45. Systemic and local delivery of TNAP significantly increased alveolar bone volume (20% and 37%, respectively) and cementum thickness (3- and 42-fold) in Ibsp^-/- mice, with evidence for periodontal ligament attachment and bone/cementum marker localization. Local delivery significantly increased regenerated cementum and bone in WT mice. Addition of 100-μg/mL bovine intestinal ALP to culture media to increase ALP in vitro increased media P_i concentration, mineralization, and Spp1 and Dmp1 marker gene expression in WT and Ibsp^-/- OCCM.30 cementoblasts. Use of phosphonoformic acid, a nonspecific inhibitor of sodium P_i cotransport, indicated that effects of bovine intestinal ALP on mineralization and marker gene expression were in part through P_i transport. These findings show for the first time through multiple in vivo and in vitro approaches that pharmacologic modulation of P_i/PP_i metabolism can overcome periodontal breakdown and accomplish regeneration.

Bone Matrix Non-Collagenous Proteins in Tissue Engineering: Creating New Bone by Mimicking the Extracellular Matrix

Engineering biomaterials that mimic the extracellular matrix (ECM) of bone is of significant importance since most of the outstanding properties of the bone are due to matrix constitution. Bone ECM is composed of a mineral part comprising hydroxyapatite and of an organic part of primarily collagen with the rest consisting on non-collagenous proteins. Collagen has already been described as critical for bone tissue regeneration; however, little is known about the potential effect of non-collagenous proteins on osteogenic differentiation, even though these proteins were identified some decades ago. Aiming to engineer new bone tissue, peptide-incorporated biomimetic materials have been developed, presenting improved biomaterial performance. These promising results led to ongoing research focused on incorporating non-collagenous proteins from bone matrix to enhance the properties of the scaffolds namely in what concerns cell migration, proliferation, and differentiation, with the ultimate goal of designing novel strategies that mimic the native bone ECM for bone tissue engineering applications. Overall, this review will provide an overview of the several non-collagenous proteins present in bone ECM, their functionality and their recent applications in the bone tissue (including dental) engineering field.

Delta-1 Functionalized Hydrogel Promotes hESC-Cardiomyocyte Graft Proliferation and Maintains Heart Function Post-Injury

Current cell transplantation techniques are hindered by small graft size, requiring high cell doses to achieve therapeutic cardiac remuscularization. Enhancing the proliferation of transplanted human embryonic stem cell-derived cardiomyocytes (hESC-CMs) could address this, allowing an otherwise subtherapeutic cell dose to prevent disease progression after myocardial infarction. In this study, we designed a hydrogel that activates Notch signaling through 3D presentation of the Notch ligand Delta-1 to use as an injectate for transplanting hESC-CMs into the infarcted rat myocardium. After 4 weeks, hESC-CM proliferation increased 2-fold and resulted in a 3-fold increase in graft size with the Delta-1 hydrogel compared to controls. To stringently test the effect of Notch-mediated graft expansion on long-term heart function, a normally subtherapeutic dose of hESC-CMs was implanted into the infarcted myocardium and cardiac function was evaluated by echocardiography. Transplantation of the Delta-1 hydrogel + hESC-CMs augmented heart function and was significantly higher at 3 months compared to controls. Graft size and hESC-CM proliferation were also increased at 3 months post-implantation. Collectively, these results demonstrate the therapeutic approach of a Delta-1 functionalized hydrogel to reduce the cell dose required to achieve functional benefit after myocardial infarction by enhancing hESC-CM graft size and proliferation.

Adaptation of MC3T3 cell line to Dulbecco's Modified Eagle's medium

Seeding cells directly into a new medium subjects the cells to stress due to certain differences in medium formulation. As a result, it seems necessary for cells to be adapted to a new medium, in order to save the properties of the cells and to achieve reliable results from the tests. The MC3T3 osteoblastic cell line is recommended to be cultured in Alpha Minimum Essential Medium (α-MEM). However, Dulbecco's Modified Eagle's medium (DMEM) is widely used for its culture. Therefore, in the present paper, two sequential methodologies were applied to adapt the MC3T3 cells to DMEM. In sequential adaptation 1, 10 vol.% DMEM was added to the original medium every day, while in sequential adaptation 2, the old medium was changed to a new medium having 20 vol.% higher DMEM content after each passage. Cells were monitored and compared to direct cell adaptation, while they were growing. The results showed that in the direct cell adaptation, increase in the number of cells was very slow. In contrast, the two sequential adaptation processes were more efficient where sequential adaptation 2 resulted in a higher number of cells in fewer days; 88 % greater than sequential adaptation 1 when it was believed that the cells were adapted. Furthermore, the statistical analysis was conducted by stepwise regression analysis and mathematical models were provided, which can predict the number of cells by day of culture.

Preparation and characterization of Jagged1-bound fibrinogen-based microspheres and their cytotoxicity against human dental pulp cells

Surface immobilization of Jagged1 promotes odonto/osteogenic differentiation in human dental pulp cells. On the contrary, soluble Jagged1 fails to activate target gene expression of Notch signaling which is important for differentiation of human dental pulp cells. Hence, Jagged1 delivery system is indeed required for transportation of immobilized Jagged1 to promote odontogenic differentiation of human dental pulp cells in vivo. The present study described the preparation and characterization of Jagged1-bound fibrinogen-based microspheres. Water-in-oil emulsion technique was employed to prepare fibrinogen microspheres and thrombin cross-linked fibrinogen microspheres. The average size of fibrinogen microspheres and thrombin cross-linked fibrinogen microspheres was 213.9 ± 35.9 and 199.9 ± 41.9 µm, respectively. These microspheres did not alter the human dental pulp cells’ cell viability. Human dental pulp cells were able to attach and spread on these microspheres. Jagged1 was conjugated on microspheres using 1-ethyl-3-(3-dimethylamino) propyl carbodiimide/N-hydroxysuccinimide. Binding capacity of Jagged1 on both fibrinogen microspheres and thrombin cross-linked fibrinogen microspheres ranged from 25.8 ± 6.0 to 35.6 ± 9.1%. There was no significant difference in the size of microspheres between before and after Jagged1 conjugation process. In conclusion, fibrinogen microspheres and thrombin cross-linked fibrinogen microspheres could be utilized as the alternative biomaterials for Jagged1 delivery for future biomedical application.

Catalytic Biosensors from Complex Coacervate Core Micelle (C3M) Thin Films

Enzymes have been applied to a variety of industrially and medically relevant chemistries as both catalysts and sensors. Incorporation of proteins and enzymes into complex coacervates has been demonstrated to improve the thermal, chemical, and temporal stability of enzymes in solution. In this work, a neutral-cationic block copolymer and an enzyme, alkaline phosphatase, are incorporated into complex coacervate core micelles (C3Ms) and coated onto a solid substrate to create a biocatalytic film from aqueous solution. The incorporation of photo-cross-linkable groups into the neutral block of the polymer allows the film to be cross-linked under ultraviolet light, rendering it insoluble. The morphology of the film is shown to depend most strongly on the protein loading within the film, while solvent annealing is shown to have a minimal effect. These films are then demonstrated as specific sensors for Zn²⁺ in solution in the presence of other metals, a model reaction for ion-selective heavy metal biosensing useful in environmental monitoring. They are shown to have low leaching and maintain sufficient activity and response for sensing for 1 month after aging under ambient conditions and at 40 °C and 50% relative humidity. The C3M immobilization method demonstrated can be applied to a wide variety of proteins with minimal chemical or genetic modification and could be used for immobilization of charged macromolecules in general to produce a wide variety of thin-film devices.

Basic fibroblast growth factor regulates phosphate/pyrophosphate regulatory genes in stem cells isolated from human exfoliated deciduous teeth

Background

Basic fibroblast growth factor (bFGF) regulates maintenance of stemness and modulation of osteo/odontogenic differentiation and mineralization in stem cells from human exfoliated deciduous teeth (SHEDs). Mineralization in the bones and teeth is in part controlled by pericellular levels of inorganic phosphate (P_i), a component of hydroxyapatite, and inorganic pyrophosphate (PP_i), an inhibitor of mineralization. The progressive ankylosis protein (gene ANKH; protein ANKH) and ectonucleotide pyrophosphatase phosphodiesterase 1 (ENPP1/ENPP1) increase PP_i and inhibit mineralization, while tissue-nonspecific alkaline phosphatase (ALPL; TNAP) is a critical pro-mineralization enzyme that hydrolyzes PP_i. We hypothesized that regulation by bFGF of mineralization in SHEDs occurs by modulation of P_i/PP_i-associated genes.

Methods

Cells were isolated from human exfoliated deciduous teeth and characterized for mesenchymal stem cell characteristics. Cells were treated with bFGF, and the osteogenic differentiation ability was determined. The mRNA expression was evaluated using real-time polymerase chain reaction. The mineralization was examined using alizarin red S staining.

Results

Cells isolated from primary teeth expressed mesenchymal stem cell markers, CD44, CD90, and CD105, and were able to differentiate into osteo/odontogenic and adipogenic lineages. Addition of 10 ng/ml bFGF to SHEDs during in vitro osteo/odontogenic differentiation decreased ALPL mRNA expression and ALP enzyme activity, increased ANKH mRNA, and decreased both P_i/PP_i ratio and mineral deposition. Effects of bFGF on ALPL and ANKH expression were detected within 24 h. Addition of 20 mM fibroblast growth factor receptor (FGFR) inhibitor SU5402 revealed the necessity of FGFR-mediated signaling, and inclusion of 1 μg/ml cyclohexamide (CHX) implicated the necessity of protein synthesis for effects on ALPL and ANKH. Addition of exogenous 10 μm PP_i inhibited mineralization and increased ANKH, collagen type 1a1 (COL1A1), and osteopontin (SPP1) mRNA, while addition of exogenous P_i increased mineralization and osterix (OSX), ANKH, SPP1, and dentin matrix protein 1 (DMP1) mRNA. The effects of PP_i and P_i on mineralization could be replicated by short-term 3- and 7-day treatments, suggesting signaling effects in addition to physicochemical regulation of mineral deposition.

Conclusion

This study reveals for the first time the effects of bFGF on P_i/PP_i regulators in SHEDs and implicates these factors in how bFGF directs osteo/odontogenic differentiation and mineralization by these cells.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1093-9) contains supplementary material, which is available to authorized users.

Halloysite-alkaline phosphatase system-A potential bioactive component of scaffold for bone tissue engineering

Alkaline phosphatase (ALP) was sucessfully incorporated into the halloysite (HAL) nanotubes, as confirmed by FTIR-ATR and XRD analyses. The loading efficiency (LE) of ALP was found to be 13.5%, while its encapsulation efficiency (EE) was estimated to be around 27%, as determined using the Bradford test. The influence of the immobilization in HAL on the enzyme activity was measured using standard ALP activity assay. Immobilized ALP effectively induced the bomineralization process, as showed by SEM, EDS, and XRD studies. As a result, calcium phosphate was produced in the form of hydroxyapatite cauliflower-like structures, with a slight content of calcium hydroxide. Interestingly, the encapsulation of ALP guest molecules in the HAL nanotubes considerably increased its thermal stability, most probably due to the heat sink effect. The activity of HAL-bound ALP was also found to be pH-independent in the wide range of pH values (3-10) due to the amphoteric nature of the aluminum oxide lining the HAL nanotube internal surface. Due to an increased resistance to the unfavorable conditions, which are often encountered during scaffold preparation or sterilization, ALP-HAL nanocomposite material may constitute an attractive bioactive component of the scaffolds for bone regeneration.

Alkaline Phosphatase Immobilization on New Chitosan Membranes with Mg2+ for Biomedical Applications

In this paper, we present the fabrication and characterization of new chitosan-based membranes while using a new biotechnology for immobilizing alkaline phosphatase (ALP). This technology involved metal ions incorporation to develop new biopolymeric supports. The chemical structure and morphological characteristics of proposed membranes were evaluated by infrared spectroscopy (FT-IR) and the scanning electron microscopy technique (SEM). The inductively coupled plasma mass spectrometry (ICP-MS) evidenced the metal ion release in time. Moreover, the effect of Mg²⁺ on the enzymatic activity and the antibacterial investigations while using Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria, hemolysis, and biocompatibility behavior were studied. Immobilizing ALP into the chitosan membranes composition followed by the incorporation of Mg²⁺ led to polymeric supports with enhanced cellular viability when comparing to chitosan-based membranes without Mg²⁺. The results obtained evidenced promising performance in biomedical applications for the new biopolymeric supports that are based on chitosan, ALP, and metal ions.

Gelatin/PVA scaffolds fabricated using a 3D-printing process employed with a low-temperature plate for hard tissue regeneration: Fabrication and characterizations

Tissue engineering aims to repair or replace damaged tissues or organs using biomedical scaffolds cultured with cells. The scaffolds composed of biomaterials should guide the cells to mature into functional tissues or organs. An ideal scaffold to regenerate hard tissues should have mechanical stability as well as biocompatibilities. It has been well known that gelatin can provide outstanding biological activities, but its low mechanical stability can be one of obstacles to be used in hard tissue regeneration. To overcome the issue, we used PVA, which can reinforce the low mechanical stability of the gelatin. The gelatin/PVA scaffolds have been fabricated using a low temperature 3D-printing process. By manipulating various weight fractions of PVA/gelatin, we can obtain the optimal mixture ratio in aspect of the physical and biological properties of the scaffolds. As a result, a weight fraction of 5:5 showed appropriate mechanical strength and enhanced cell activities, such as cell proliferation and differentiation. The gelatin/PVA scaffold showed potential for future application as biomedical scaffold in soft and hard tissue regeneration.

Electrospun Silk Fibroin Nanofibrous Scaffolds with Two-Stage Hydroxyapatite Functionalization for Enhancing the Osteogenic Differentiation of Human Adipose-Derived Mesenchymal Stem Cells

The development of functional scaffolds with improved osteogenic potential is important for successful bone formation and mineralization in bone tissue engineering. In this study, we developed a functional electrospun silk fibroin (SF) nanofibrous scaffold functionalized with two-stage hydroxyapatite (HAp) particles, using mussel adhesive-inspired polydopamine (PDA) chemistry. HAp particles were first incorporated into SF scaffolds during the electrospinning process, and then immobilized onto the electrospun SF nanofibrous scaffolds containing HAp via PDA-mediated adhesive chemistry. We obtained two-stage HAp-functionalized SF nanofibrous scaffolds with improved mechanical properties and capable of providing a bone-specific physiological microenvironment. The developed scaffolds were tested for their ability to enhance the osteogenic differentiation of human adipose-derived mesenchymal stem cells (hADMSCs) in vitro and repair bone defect in vivo. To boost their ability for bone repair, we genetically modified hADMSCs with the transcriptional coactivator with PDZ-binding motif (TAZ) via polymer nanoparticle-mediated gene delivery. TAZ is a well-known transcriptional modulator that activates the osteogenic differentiation of mesenchymal stem cells (MSCs). Two-stage HAp-functionalized SF scaffolds significantly promoted the osteogenic differentiation of TAZ-transfected hADMSCs in vitro and enhanced mineralized bone formation in a critical-sized calvarial bone defect model. Our study shows the potential utility of SF scaffolds with nanofibrous structures and enriched inorganic components in bone tissue engineering.

Lipogels responsive to near-infrared light for the triggered release of therapeutic agents

Here we report a composite system based on fibrin hydrogels that incorporate in their structure near-infrared (NIR) responsive nanomaterials and thermosensitive liposomes (TSL). Polymerized fibrin networks entrap simultaneously gold-based nanoparticles (NPs) capable of transducing NIR photon energy into heat, and lysolipid-incorporated TSL (LTSL) loaded with doxorubicin hydrochloride (DOX). NIR irradiation of the resulting hydrogels (referred to as "lipogels") with 808nm laser light increased the temperature of the illuminated areas, leading to the release of the liposomal cargo. Levels of DOX that release from the "smart" composites were dependent on the concentration of NIR nanotransducers loaded in the lipogel, the intensity of the electromagnetic energy deposited and the irradiation regime. Released DOX retained its bioactivity, as shown in cultures of epithelial carcinoma cells. Finally, the developed drug delivery platform was refined by using NIR-photoabsorbers based on copper sulfide NPs to generate completely biodegradable composites as well as through the incorporation of cholesterol (Ch) in LTSL formulation, which lessens leakiness of the liposomal cargo at physiological temperature. This remotely controlled system may suit well for those therapies that require precise control over the dose of delivered drug in a defined spatiotemporal framework.

STATEMENT OF SIGNIFICANCE

Hydrogels composed of fibrin embedding nanoparticles responsive to near infrared (NIR) energy and thermosensitive liposomes loaded with doxorubicin hydrochloride (DOX), were prepared by in situ polymerization. NIR-light irradiation of these constructs, referred to as "NIR responsive lipogels", results in the controlled release of DOX to the surrounding medium. This technology may use fully degradable components and can preserve the bioactivity of liposomal cargo after remote triggering to finely regulate the dose and bioavailability of delivered payloads. NIR responsive lipogels technology overcomes the limitations of drug release systems based on the combination of liposomes and degradable polymeric materials, which in many cases lead to insufficient release at therapy onset or to overdose during high degradation period.

Effects of the incorporation of ε-aminocaproic acid/chitosan particles to fibrin on cementoblast differentiation and cementum regeneration

Cementum formation on the exposed tooth-root surface is a critical process in periodontal regeneration. Although various therapeutic approaches have been developed, regeneration of integrated and functional periodontal complexes is still wanting. Here, we found that the OCCM30 cementoblasts cultured on fibrin matrix express substantial levels of matrix proteinases, leading to the degradation of fibrin and the apoptosis of OCCM30 cells, which was reversed upon treatment with a proteinase inhibitor, ε-aminocaproic acid (ACA). Based on these findings, ACA-releasing chitosan particles (ACP) were fabricated and ACP-incorporated fibrin (fibrin-ACP) promoted the differentiation of cementoblasts in vitro, as confirmed by bio-mineralization and expressions of molecules associated with mineralization. In a periodontal defect model of beagle dogs, fibrin-ACP resulted in substantial cementum formation on the exposed root dentin in vivo, compared to fibrin-only and enamel matrix derivative (EMD) which is used clinically for periodontal regeneration. Remarkably, the fibrin-ACP developed structural integrations of the cementum-periodontal ligament-bone complex by the Sharpey's fiber insertion. In addition, fibrin-ACP promoted alveolar bone regeneration through increased bone volume of tooth roof-of-furcation defects and root coverage. Therefore, fibrin-ACP can promote cementogenesis and osteogenesis by controlling biodegradability of fibrin, implicating the feasibility of its therapeutic use to improve periodontal regeneration.

STATEMENT OF SIGNIFICANCE

Cementum, the mineralized layer on root dentin surfaces, functions to anchor fibrous connective tissues on tooth-root surfaces with the collagenous Sharpey's fibers integration, of which are essential for periodontal functioning restoration in the complex. Through the cementum-responsible fiber insertions on tooth-root surfaces, PDLs transmit various mechanical responses to periodontal complexes against masticatory/occlusal stimulations to support teeth. In this study, periodontal tissue regeneration was enhanced by use of modified fibrin biomaterial which significantly promoted cementogenesis within the periodontal complex with structural integration by collagenous Sharpey's fiber insertions in vivo by controlling fibrin degradation and consequent cementoblast apoptosis. Furthermore, the modified fibrin could improve repair and regeneration of tooth roof-of-furcation defects, which has spatial curvatures and geometrical difficulties and hardly regenerates periodontal tissues.