Effect of bioactive extruded PLA/HA composite films on focal adhesion formation of preosteoblastic cells

NOVEL HIGH-STRENGTH POLYESTER COMPOSITE SCAFFOLDS FOR BONE REGENERATION

Repair of critical sized bone defects, particularly in load-bearing areas, is a major clinical problem that requires surgical intervention and implantation of biological or engineered grafts. For load-bearing sites, it is essential to use engineered grafts that have both sufficient mechanical strength and appropriate pore properties to support bone repair and tissue regeneration. Unfortunately, the mechanical properties of such grafts are often compromised due to the creation of pores required to facilitate tissue ingrowth following implantation. To overcome the limitations associated with porous scaffolds and their reduced mechanical strength, we have developed a methodology for creating a solid structure that retains its bulk mechanical properties while also evolving into a porous structure in a biological environment through degradation and erosion. In this study, we utilized polyesters that have been approved by the FDA, including poly (lactic acid) (PLA), poly(glycolic acid) (PGA), their copolymer PLGA (PLGA, with a ratio of 85:15 and 50:50 of PLA:PGA), and poly(caprolactone) (PCL). These polymers and their ceramic composites with tricalcium phosphate (TCP) were compression molded into solid forms, which exhibited mechanical properties with compressive modulus as high as 2745 ± 364 MPa within the range of human trabecular bone and in the lower range of human cortical bone. The use of fast-degrading PLGA (50:50) and PGA as porogens allowed the formation of pores within the solid structures due to their degradation, and the TCP acts as a buffering agent to neutralize their acidic degradation byproducts. These scaffolds facilitated the growth of new blood vessels and tissue ingrowth in a subcutaneous implantation model. In addition, in a rat critical-sized mandibular bone defects these scaffolds supported bone growth with 70% of new bone volume fraction. Furthermore, the extent of bone regeneration was found to be higher for the scaffolds with bone morphogenic proteins (BMP2), indicating their suitability for bone repair and regeneration.

Surface Functionalization of Poly(lactic acid) via Deposition of Hydroxyapatite Monolayers for Biomedical Applications

The surface modification of poly(lactic acid) (PLA) using hydroxyapatite (HAP) particles via Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) approaches has been reported. The HAP monolayer was characterized at the air/water interface and deposited on three-dimensional (3D) printed poly(lactic acid). The deposition of HAP particles using the LS approach led to a larger surface coverage in comparison to the LB method, which produces a less uniform coating because of the aggregation of the particles. After the transfer of HAP on the PLA surface, the wettability values remained within the desired range. The presence of HAP on the surface of the polymer altered the topography and roughness in the nanoscale, as evidenced by the atomic force microscopy (AFM) images. This effect can be beneficial for the osteointegration of polymeric implants at an early stage, as well as for the reduction of the adherence of the microbial biofilm. Overall, the results suggest that the LS technique could be a promising approach for surface modification of PLA by hydroxyapatite with respective advantages in the biomedical field.

3D printed polylactic acid/gelatin-nano-hydroxyapatite/platelet-rich plasma scaffold for critical-sized skull defect regeneration

BACKGROUND

Three-dimensional (3D) printing is a capable approach for the fabrication of bone tissue scaffolds. Nevertheless, a purely made scaffold such as polylactic acid (PLA) may suffer from shortcomings and be restricted due to its biological behavior. Gelatin, hydroxyapatite and platelet-rich plasma (PRP) have been revealed to be of potential to enhance the osteogenic effect. In this study, it was tried to improve the properties of 3D-printed PLA scaffolds by infilling them with gelatin-nano-hydroxyapatite (PLA/G-nHA) and subsequent coating with PRP. For comparison, bare PLA and PLA/G-nHA scaffolds were also fabricated. The printing accuracy, the scaffold structural characterizations, mechanical properties, degradability behavior, cell adhesion, mineralization, systemic effect of the scaffolds on the liver enzymes, osteocalcin level in blood serum and in vivo bone regeneration capability in rat critical-sized calvaria defect were evaluated.

RESULTS

High printing accuracy (printing error of < 11%) was obtained for all measured parameters including strut thickness, pore width, scaffold density and porosity%. The highest mean ultimate compression strength (UCS) was associated with PLA/G-nHA/PRP scaffolds, which was 10.95 MPa. A slow degradation rate was observed for all scaffolds. The PLA/G-nHA/PRP had slightly higher degradation rate, possibly due to PRP release, with burst release occurred at week 4. The MTT results showed that PLA/G-nHA/PRP provided the highest cell proliferation at all time points, and the serum biochemistry (ALT and AST level) results indicated no abnormal/toxic influence caused by scaffold biomaterials. Superior cell adhesion and mineralization were obtained for PLA/G-nHA/PRP. Furthermore, all the developed scaffolds showed bone repair capability. The PLA/G-nHA/PRP scaffolds could better support bone regeneration than bare PLA and PLA/G-nHA scaffolds.

CONCLUSION

The PLA/G-nHA/PRP scaffolds can be considered as potential for hard tissue repair.

Properties of poly(lactic acid)/walnut shell/hydroxyapatite composites prepared with fused deposition modeling

In this work, fused deposition modeling (FDM) technology was used to prepare poly(lactic acid)/walnut shell/hydroxyapatite (PLA/WS/HA) composite filaments. HA was treated with silane and characterized by Fourier transform infrared spectroscopy (FTIR). The composites were investigated by using simultaneous thermal analyzer, scanning electron microscopy (SEM) and a universal mechanical testing machine. The results showed that incorporating either HA or WS improved the thermal stability and water absorption of PLA, but lowered the tensile and compression strength. Fillers toughened the PLA matrix, resulting in higher tensile elongation and compressive strain. The tensile and compressive strengths of samples significantly dropped after water-immersion for 6 weeks. Finally, scaffolds were manufactured by using FDM. The compression modulus and structural feature of scaffolds indicated that the PLA/WS/HA composites have the potential to be applied in structural parts, such as bone implants.

The healing of bone defects by cell-free and stem cell-seeded 3D-printed PLA tissue-engineered scaffolds

In this paper, the in-vivo healing of critical-sized bony defects by cell-free and stem cell-seeded 3D-printed PLA scaffolds was studied in rat calvaria bone. The scaffolds were implanted in the provided defect sites and histological analysis was conducted after 8 and 12 weeks. The results showed that both cell-free and stem cell-seeded scaffolds exhibited superb healing compared with the empty defect controls, and new bone and connective tissues were formed in the healing site after 8 and 12 weeks, postoperatively. The higher filled area, bone formation and bone maturation were observed after 12 weeks, particularly for PLA + Cell scaffolds.

Restorative biodegradable two-layered hybrid microneedles for melanoma photothermal/chemo co-therapy and wound healing

Tumor killing and wound healing are two complementary and influential processes during the treatment of melanoma. Herein, a two-layered microneedle platform was developed with bifunctional effect of chemo-photothermal synergistic melanoma therapy and skin regeneration. The bifunctional platform composed of embeddable curcumin nanodrugs/new Indocyanine Green/hyaluronic acid (Cur NDs/IR820/HA) microneedles and sodium alginate/gelatin/hyaluronic acid (SA/Ge/HA) supporting backing layer was prepared through a two-step casting process. With uniform incorporation of curcumin nanodrugs and IR820, the microneedles exhibited excellent photothermal performance under external near-infrared (NIR) light stimulation and tumor co-therapy ability. Once the embeddable microneedles were inserted into skin, they would rapidly dissolve and activate drug release successfully for tumor treatment. Moreover, the SA/Ge/HA supporting backing layer was left behind to cover the wound and promote the proliferation of endothelial and fibroblasts cells for enhanced skin regeneration. The two-layered microneedles platform can simultaneously eliminate the tumor and accelerate wounding healing, which may be potentially employed as a competitive strategy for the treatment of melanoma.

Osteoblast Attachment on Titanium Coated with Hydroxyapatite by Atomic Layer Deposition

Background: The increasing demand for bone implants with improved osseointegration properties has prompted researchers to develop various coating types for metal implants. Atomic layer deposition (ALD) is a method for producing nanoscale coatings conformally on complex three-dimensional surfaces. We have prepared hydroxyapatite (HA) coating on titanium (Ti) substrate with the ALD method and analyzed the biocompatibility of this coating in terms of cell adhesion and viability. Methods: HA coatings were prepared on Ti substrates by depositing CaCO₃ films by ALD and converting them to HA by wet treatment in dilute phosphate solution. MC3T3-E1 preosteoblasts were cultured on ALD-HA, glass slides and bovine bone slices. ALD-HA and glass slides were either coated or non-coated with fibronectin. After 48h culture, cells were imaged with scanning electron microscopy (SEM) and analyzed by vinculin antibody staining for focal adhesion localization. An 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) test was performed to study cell viability. Results: Vinculin staining revealed similar focal adhesion-like structures on ALD-HA as on glass slides and bone, albeit on ALD-HA and bone the structures were thinner compared to glass slides. This might be due to thin and broad focal adhesions on complex three-dimensional surfaces of ALD-HA and bone. The MTT test showed comparable cell viability on ALD-HA, glass slides and bone. Conclusion: ALD-HA coating was shown to be biocompatible in regard to cell adhesion and viability. This leads to new opportunities in developing improved implant coatings for better osseointegration and implant survival.

Comparison of globular albumin methacryloyl and random-coil gelatin methacryloyl: Preparation, hydrogel properties, cell behaviors, and mineralization

Bovine serum albumin methacryloyl (BSAMA) is a newly emerging photocurable globular protein-based material whereas gelatin methacryloyl (GelMA) is one of the most popular photocurable fibrous protein-based materials. So far, the influence of their different structural conformations as building blocks on hydrogel properties and mineral deposition has not been investigated. Here, we compared their differences in structures, gelation kinetics, hydrogel properties, mineralization, and cell behaviors. BSAMA maintained a stable globular structure while GelMA exhibited temperature-sensitive conformations (4 - 37 °C). BSAMA displayed slower gelation kinetics and much more retarded enzymatic degradation compared to GelMA. Photocurable BSAMA (6.41 - 390.95 kPa) and GelMA hydrogels (36.09 - 199.70 kPa) exhibited tunable mechanical properties depending on their concentrations (10 - 20%). Interestingly, BSAMA hydrogels mineralized needle-like apatite (Ca/P: 1.409) with higher crystallinity compared to GelMA hydrogels (Ca/P: 1.344). BSAMA and GelMA supported satisfactory cell (MC3T3-L1) viability of 99.43 ± 0.57% and 97.14 ± 0.69%, respectively. However, BSAMA gels were less favorable to cell proliferation and migration than GelMA gels. In serum-free environments, cells on GelMA displayed a higher amount of attachment, a more elongated shape, and a longer protrusion compared to those on BSAMA (p < 0.01) during the early adhesion.

Characterisation of Selected Materials in Medical Applications

Tissue engineering is an interdisciplinary field of science that has developed very intensively in recent years. The first part of this review describes materials with medical and dental applications from the following groups: metals, polymers, ceramics, and composites. Both positive and negative sides of their application are presented from the point of view of medical application and mechanical properties. A variety of techniques for the manufacture of biomedical components are presented in this review. The main focus of this work is on additive manufacturing and 3D printing, as these modern techniques have been evaluated to be the best methods for the manufacture of medical and dental devices. The second part presents devices for skull bone reconstruction. The materials from which they are made and the possibilities offered by 3D printing in this field are also described. The last part concerns dental transitional implants (scaffolds) for guided bone regeneration, focusing on polylactide-hydroxyapatite nanocomposite due to its unique properties. This section summarises the current knowledge of scaffolds, focusing on the material, mechanical and biological requirements, the effects of these devices on the human body, and their great potential for applications.

3D-Printed PCL Scaffolds Coated with Nanobioceramics Enhance Osteogenic Differentiation of Stem Cells

With advances in bone tissue engineering, various materials and methods have been explored to find a better scaffold that can help in improving bone growth and regeneration. Three-dimensional (3D) printing by fused deposition modeling can produce customized scaffolds from biodegradable polyesters such as polycaprolactone (PCL). Although the fabricated PCL scaffolds exhibited a lack of bioactivity and poor cell attachment on their surfaces, herein, using a simple postfabrication modification method with hydroxyapatite (HA) and bioglasses (BGs), we obtained better cell proliferation and attachment. Biological behavior and osteosupportive capacity of the 3D-printed scaffolds including PCL, PCL/HA, PCL/BG, and PCL/HA/BG were evaluated in this study, while human adipose tissue-derived mesenchymal stem cells (hADSCs) were cultured on the scaffolds. The cell morphology, attachment, and proliferation were investigated using scanning electron microscopy (SEM), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, and 4',6-diamidino-2-phenylindole (DAPI) staining. In the next step, the ability of stem cells to differentiate into osteoblasts was evaluated by measuring alkaline phosphatase (ALP) activity, calcium deposition, and bone-related gene and protein expression. In the end, the expression levels of miR-20a, miR-125a, and their target genes were also investigated as positive and negative regulators in osteogenesis pathways. The results showed that the coated scaffolds with bioceramics present a more appropriate surface for cell adhesion and proliferation, as well as efficient potential in inducing osteoconduction and osteointegration compared to PCL alone and control. The PCL/HA/BG scaffold exhibited higher in vitro cell viability and bone formation compared to the other groups, which can be due to the synergistic effect of HA and BG. On the whole, this tricomponent 3D-printing scaffold has a promising prospect for bone tissue engineering applications.

Comparative Study of Crystallization, Mechanical Properties, and In Vitro Cytotoxicity of Nanocomposites at Low Filler Loadings of Hydroxyapatite for Bone-Tissue Engineering Based on Poly(l-lactic acid)/Cyclo Olefin Copolymer

A poly(l-lactic acid)/nanohydroxyapatite (PLLA/nHA) scaffold works as a bioactive, osteoconductive scaffold for bone-tissue engineering, but its low degradation rate limits embedded HA in PLLA to efficiently interact with body fluids. In this work, nano-hydroxyapatite (nHA) was added in lower filler loadings (1, 5, 10, and 20 wt%) in a poly(l-lactic acid)/cyclo olefin copolymer10 wt% (PLLA/COC10) blend to obtain novel poly(l-lactic acid)/cyclo olefin copolymer/nanohydroxyapatite (PLLA/COC10-nHA) scaffolds for bone-tissue regeneration and repair. Furthermore, the structure-activity relationship of PLLA/COC10-nHA (ternary system) nanocomposites in comparison with PLLA/nHA (binary system) nanocomposites was systematically studied. Nanocomposites were evaluated for structural (morphology, crystallization), thermomechanical properties, antibacterial potential, and cytocompatibility for bone-tissue engineering applications. Scanning electron microscope images revealed that PLLA/COC10-nHA had uniform morphology and dispersion of nanoparticles up to 10% of HA, and the overall nHA dispersion in matrix was better in PLLA/COC10-nHA as compared to PLLA/nHA. Fourier transformation infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), and differential scanning calorimetry (DSC) studies confirmed miscibility and transformation of the α-crystal form of PLLA to the ά-crystal form by the addition of nHA in all nanocomposites. The degree of crystallinity (%) in the case of PLLA/COC10-nHA 10 wt% was 114% higher than pure PLLA/COC10 and 128% higher than pristine PLLA, indicating COC and nHA are acting as nucleating agents in the PLLA/COC10-nHA nanocomposites, causing an increase in the degree of crystallinity (%). Moreover, PLLA/COC10-nHA exhibited 140 to 240% (1-20 wt% HA) enhanced mechanical properties in terms of ductility as compared to PLLA/nHA. Antibacterial activity results showed that 10 wt% HA in PLLA/COC10-nHA showed substantial activity against P. aeruginosa, S. aureus, and L. monocytogenes. In vitro cytocompatibility of PLLA/COC10 and PLLA nanocomposites with nHA osteoprogenitor cells (MC3T3-E1) and bone mesenchymal stem cells (BMSC) was evaluated. Both cell lines showed two- to three-fold enhancement in cell viability and 10- to 30-fold in proliferation upon culture on PLLA/COC10-nHA as compared to PLLA/nHA composites. It was observed that the ternary system PLLA/COC10-nHA had good dispersion and interfacial interaction resulting in improved thermomechanical and enhanced osteoconductive properties as compared to PLLA/nHA.

The effect of enhanced bone marrow in conjunction with 3D-printed PLA-HA in the repair of critical-sized bone defects in a rabbit model

Background

Traditionally, the iliac crest has been the most common harvesting site for autologous bone grafts; however, it has some limitations, including poor bone availability and donor-site morbidity. This study sought to explore the effect of enhanced bone marrow (eBM) in conjunction with three-dimensional (3D)-printed polylactide–hydroxyapatite (PLA-HA) scaffolds in the repair of critical-sized bone defects in a rabbit model.

Methods

First, 3D-printed PLA-HA scaffolds were fabricated and evaluated using micro-computed tomography (µCT) and scanning electron microscopy (SEM). Twenty-seven New Zealand white rabbits were randomly divided into 3 groups (n=9 per group), and the defects were treated using 3D-printed PLA-HA scaffolds (the PLA-HA group) or eBM in conjunction with 3D-printed PLA-HA scaffolds (the PLA-HA/eBM group), or were left untreated (the control group). Radiographic, µCT, and histological analyses were performed to evaluate bone regeneration in the different groups.

Results

The 3D-printed PLA-HA scaffolds were cylindrical, and had a mean pore size of 500±47.1 µm and 60%±3.5% porosity. At 4 and 8 weeks, the lane-sandhu X-ray score in the PLA-HA/eBM group was significantly higher than that in the PLA-HA group and the control group (P<0.01). At 8 weeks, the µCT analysis showed that the bone volume (BV) and bone volume/tissue volume (BV/TV) in the PLA-HA/eBM group were significantly higher than those in the PLA-HA group and the control group (P<0.01). Hematoxylin and eosin staining indicated that the new bone area in the PLA-HA/eBM group was significantly higher than that in the PLA-HA group and the control group (P<0.01).

Conclusions

The group that was treated with eBM in conjunction with 3D-printed PLA-HA showed enhanced bone repair compared to the other 2 groups. PLA-HA/eBM scaffolds represent a promising way to treat critical-sized bone defects.

Biodegradable materials for bone defect repair

Compared with non-degradable materials, biodegradable biomaterials play an increasingly important role in the repairing of severe bone defects, and have attracted extensive attention from researchers. In the treatment of bone defects, scaffolds made of biodegradable materials can provide a crawling bridge for new bone tissue in the gap and a platform for cells and growth factors to play a physiological role, which will eventually be degraded and absorbed in the body and be replaced by the new bone tissue. Traditional biodegradable materials include polymers, ceramics and metals, which have been used in bone defect repairing for many years. Although these materials have more or fewer shortcomings, they are still the cornerstone of our development of a new generation of degradable materials. With the rapid development of modern science and technology, in the twenty-first century, more and more kinds of new biodegradable materials emerge in endlessly, such as new intelligent micro-nano materials and cell-based products. At the same time, there are many new fabrication technologies of improving biodegradable materials, such as modular fabrication, 3D and 4D printing, interface reinforcement and nanotechnology. This review will introduce various kinds of biodegradable materials commonly used in bone defect repairing, especially the newly emerging materials and their fabrication technology in recent years, and look forward to the future research direction, hoping to provide researchers in the field with some inspiration and reference.

Analysis of cell-biomaterial interaction through cellular bridge formation in the interface between hGMSCs and CaP bioceramics

The combination of biomaterials and stem cells for clinical applications constitute a great challenge in bone tissue engineering. Hence, cellular networks derived from cells-biomaterials crosstalk have a profound influence on cell behaviour and communication, preceding proliferation and differentiation. The purpose of this study was to investigate in vitro cellular networks derived from human gingival mesenchymal stem cells (hGMSCs) and calcium phosphate (CaP) bioceramic interaction. Biological performance of CaP bioceramic and hGMSCs interaction was evaluated through cell adhesion and distribution, cellular proliferation, and potential osteogenic differentiation, at three different times: 5 h, 1 week and 4 weeks. Results confirmed that hGMSCs met the required MSCs criteria while displaying osteogenic differentiaton capacities. We found a significant increase of cellular numbers and proliferation levels. Also, protein and mRNA OPN expression were upregulated in cells cultured with CaP bioceramic by day 21, suggesting an osteoinductible effect of the CaP bioceramic on hGMSCs. Remarkably, CaP bioceramic aggregations were obtained through hGMSCs bridges, suggesting the in vitro potential of macrostructures formation. We conclude that hGMSCs and CaP bioceramics with micro and macropores support hGMSC adhesion, proliferation and osteogenic differentiation. Our results suggest that investigations focused on the interface cells-biomaterials are essential for bone tissue regenerative therapies.

ICG-loaded gold nano-bipyramids with NIR activatable dual PTT-PDT therapeutic potential in melanoma cells

A great amount of effort is directed towards the progress of cancer treatment approaches aspiring to develop non-invasive, targeted and highly efficient therapies. In this context, Photothermal (PTT) and Photodynamic (PDT) Therapies were proven as promising. This work aims to integrate the therapeutic activities of two near-infrared (NIR) photoactive biomaterials - gold nano-bipyramids (AuBPs) and Indocyanine Green (ICG) - into one single targeted hybrid nanosystem able to operate as dual PTT-PDT agent with higher efficiency compared with each one alone. Firstly, different aspect ratio' AuBPs were systematically investigated in water solution for their intrinsic ability to efficiently generate toxic reactive oxygen species, namely oxygen singlet (¹O₂), under NIR laser irradiation, as this effect is less investigated in literature. Interestingly, the photodynamic activity of AuBPs measured by monitoring the photooxidation of 9,10-Anthracenediyl-bis(methylene)dimalonic acid (ABDA) - a well-known ¹O₂ sensor, is important, counting for 30 % decrease in ABDA optical absorbance for the most active AuBPs, well-correlating with the previously determined photothermal conversion efficiency. Furthermore, ICG was successfully grafted onto the Poly-lactic acid (PLA) coating of plasmonic nanoparticles and, consequently, the as-designed fully integrated hybrid nanosystem shows improved PTT-PDT performance in solution. Specifically, by triggering simultaneous PTT-PDT activities, the ¹O₂ amount is doubled, while the heating monitoring shows higher and faster increase in temperature compared to AuBPs alone. Finally, the efficiency of the combined PTT-PDT therapeutic activity was validated in vitro against B16-F10 cell line by covalent conjugation of the nanosystem with Folic Acid, which ensures the cellular recognition by overexpression of folate receptor.

Preparation and in vitro evaluation of PLA/biphasic calcium phosphate filaments used for fused deposition modelling of scaffolds

Ceramic materials such as calcium phosphates (CaPs) with a composition similar to the mineral phase of bones and polymeric polylactic acid (PLA) are potential candidates for the manufacturing of scaffolds to act as bone substitutes and for tissue engineering applications, due to their bioresorbability and biocompatibility. Variables such as porosity, topography, morphology, and mechanical properties play an essential role in the scaffolds response. In this paper, a polymer/ceramic composite filament of 1.7 mm in diameter based on PLA and biphasic calcium phosphates (BCPs) was obtained by hot-melt extrusion in a single screw extruder. The particles of BCP were obtained by solution-combustion synthesis, and the PLA used was commercial grade. The BCPs ceramics were characterized by X-ray diffraction (XRD), scanning electron microscopic (SEM), transmission electron microscopy (TEM), and Brunauer, Emmett, and Teller (BET). It was possible to confirm that the main inorganic phases were hydroxyapatite (HAP) and tricalcium phosphate (TCP) with grain sizes below 100 nm and with high porosity. The Filaments obtained are a bit fragile but were able to be used in fused deposition modelling (FDM) using low-cost commercial printers. The filaments were characterized by SEM and energy dispersive X-ray (EDX). The in-vitro tests of filaments showed deposition of apatite phases on their surface, non-cytotoxic behavior, adequate cell proliferation and cell adhesion.

Cornstarch-based wound dressing incorporated with hyaluronic acid and propolis: In vitro and in vivo studies

The unique physicochemical and functional characteristics of starch-based biomaterials and wound dressings have been proposed for several biomedical applications. Film dressings of cornstarch/hyaluronic acid/ ethanolic extract of propolis (CS/HA/EEP) were prepared by solvent-casting and characterized by attenuated total reflectance/Fourier transform infrared spectroscopy, scanning electron microscopy, gas chromatography/mass spectrometry, light transmission, opacity measurements, EEP release, equilibrium swelling, and in vitro and in vivo evaluations. The CS/HA/0.5%EEP film dressing exhibited higher antibacterial activity against Staphylococcus aureus (2.08 ± 0.14 mm), Escherichia coli (2.64 ± 0.18 mm), and Staphylococcus epidermidis (1.02 ± 0.15 mm) in comparison with the CS, CS/HA, and CS/HA/0.25%EEP films. Also, it showed no cytotoxicity for the L929 fibroblast cells. This wound dressing could effectively accelerate the wound healing process at Wistar rats' skin excisions. These results indicate that enrichment of cornstarch wound dressings with HA and EEP can significantly enhance their potential efficacy as wound dressing material.

A Two-Dimensional Wireless and Passive Sensor for Stress Monitoring

A new two-dimensional wireless and passive stress sensor using the inverse magnetostrictive effect is proposed, designed, analyzed, fabricated, and tested in this work. Three pieces of magnetostrictive material are bonded on the surface of a smart elastomer structure base to form the sensor. Using the external load, an amplitude change in the higher-order harmonic signal of the magnetic material is detected (as a result of the passive variation of the magnetic permeability wirelessly). The finite element method (FEM) is used to accomplish the design and analysis process. The strain-sensitive regions of the tension and torque are distributed at different locations, following the FEM analysis. After the fabrication of a sensor prototype, the mechanical output performance is measured. The effective measurement range is 0–40 N and 0–4 N·M under tension and torque, respectively. Finally, the error of the sensor after calibration and decoupling for F_x is 3.4% and for T_x is 4.2% under a compound test load (35 N and 3.5 N·M). The proposed sensor exhibits the merits of being passive and wireless, and has an ingenious structure. This passive and wireless sensor is useful for the long-term detection of mechanical loading within a moving object, and can even potentially be used for tracing dangerous overloads and for preventing implant failures by monitoring the deformation of implants in the human body.

A comprehensive review of biodegradable synthetic polymer-ceramic composites and their manufacture for biomedical applications

The application of various materials in biomedical procedures has recently experienced rapid growth. One area that is currently receiving significant attention from the scientific community is the treatment of a number of different types of bone-related diseases and disorders by using biodegradable polymer-ceramic composites. Biomaterials, the most common materials used to repair or replace damaged parts of the human body, can be categorized into three major groups: metals, ceramics, and polymers. Composites can be manufactured by combining two or more materials to achieve enhanced biocompatibility and biomechanical properties for specific applications. Biomaterials must display suitable properties for their applications, about strength, durability, and biological influence. Metals and their alloys such as titanium, stainless steel, and cobalt-based alloys have been widely investigated for implant-device applications because of their excellent mechanical properties. However, these materials may also manifest biological issues such as toxicity, poor tissue adhesion and stress shielding effect due to their high elastic modulus. To mitigate these issues, hydroxyapatite (HA) coatings have been used on metals because their chemical composition is similar to that of bone and teeth. Recently, a wide range of synthetic polymers such as poly (l-lactic acid) and poly (l-lactide-co-glycolide) have been studied for different biomedical applications, owing to their promising biocompatibility and biodegradability. This article gives an overview of synthetic polymer-ceramic composites with a particular emphasis on calcium phosphate group and their potential applications in tissue engineering. It is hoped that synthetic polymer-ceramic composites such as PLLA/HA and PCL/HA will provide advantages such as eliminating the stress shielding effect and the consequent need for revision surgery.

Osteogenic Differentiation of Human Mesenchymal Stem cells in a 3D Woven Scaffold

Fiber-based scaffolds produced by textile manufacturing technology offer versatile materials for tissue engineering applications since a wide range of crucial scaffold parameters, including porosity, pore size and interconnectivity, can be accurately controlled using 3D weaving. In this study, we developed a weavable, bioactive biodegradable composite fiber from poly (lactic acid) (PLA) and hydroxyapatite powder by melt spinning. Subsequently, scaffolds of these fibers were fabricated by 3D weaving. The differentiation of human mesenchymal stem cells (hMSCs) in vitro was studied on the 3D scaffolds and compared with differentiation on 2D substrates having the same material composition. Our data showed that the 3D woven scaffolds have a major impact on hMSCs proliferation and activation. The 3D architecture supports the differentiation of the hMSCs into osteoblast cells and enhances the production of mineralized bone matrix. The present study further confirms that a 3D scaffold promotes hMSCs differentiation into the osteoblast–lineage and bone mineralization.

Three dimensional printed polylactic acid-hydroxyapatite composite scaffolds for prefabricating vascularized tissue engineered bone: An in vivo bioreactor model

The repair of large bone defects with complex geometries remains a major clinical challenge. Here, we explored the feasibility of fabricating polylactic acid-hydroxyapatite (PLA-HA) composite scaffolds. These scaffolds were constructed from vascularized tissue engineered bone using an in vivo bioreactor (IVB) strategy with three-dimensional printing technology. Specifically, a rabbit model was established to prefabricate vascularized tissue engineered bone in two groups. An experimental group (EG) was designed using a tibial periosteum capsule filled with 3D printed (3DP) PLA-HA composite scaffolds seeded with bone marrow stromal cells (BMSCs) and crossed with a vascular bundle. 3DP PLA-HA scaffolds were also combined with autologous BMSCs and transplanted to tibial periosteum without blood vessel as a control group (CG). After four and eight weeks, neovascularisation and bone tissues were analysed by studying related genes, micro-computed tomography (Micro-CT) and histological examinations between groups. The results showed that our method capably generated vascularized tissue engineered bone in vivo. Furthermore, we observed significant differences in neovascular and new viable bone formation in the two groups. In this study, we demonstrated the feasibility of generating large vascularized bone tissues in vivo with 3DP PLA-HA composite scaffolds.

3D printing of hydroxyapatite polymer-based composites for bone tissue engineering

Skeletal defects reconstruction, using custom-made substitutes, represents a valid solution to replacing lost and damaged anatomical bone structures, renew their original function, and at the same time, restore the original aesthetic aspect. Rapid prototyping (RP) techniques allow the construction of complex physical models based on 3D clinical images. However, RP machines usually work with synthetic polymers; therefore, producing custom-made scaffolds using a biocompatible material directly by RP is an exciting challenge. The aim of the present work is to investigate the potentiality of 3D printing as a manufacturing method to produce an osteogenic hydroxyapatite-polylactic acid bone graft substitute.

Investigation of silk fibroin nanoparticle-decorated poly(l-lactic acid) composite scaffolds for osteoblast growth and differentiation

Attempts to reflect the physiology of organs is quite an intricacy during the tissue engineering process. An ideal scaffold and its surface topography can address and manipulate the cell behavior during the regeneration of targeted tissue, affecting the cell growth and differentiation significantly. Herein, silk fibroin (SF) nanoparticles were incorporated into poly(l-lactic acid) (PLLA) to prepare composite scaffolds via phase-inversion technique using supercritical carbon dioxide (SC-CO2). The SF nanoparticle core increased the surface roughness and hydrophilicity of the PLLA scaffolds, leading to a high affinity for albumin attachment. The in vitro cytotoxicity test of SF/PLLA scaffolds in L929 mouse fibroblast cells indicated good biocompatibility. Then, the in vitro interplay between mouse preosteoblast cell (MC3T3-E1) and various topological structures and biochemical cues were evaluated. The cell adhesion, proliferation, osteogenic differentiation and their relationship with the structures as well as SF content were explored. The SF/PLLA weight ratio (2:8) significantly affected the MC3T3-E1 cells by improving the expression of key players in the regulation of bone formation, ie, alkaline phosphatase (ALP), osteocalcin (OC) and collagen 1 (COL-1). These results suggest not only the importance of surface topography and biochemical cues but also the potential of applying SF/PLLA composite scaffolds as biomaterials in bone tissue engineering.

New synthesis method of HA/P(D,L)LA composites: study of fibronectin adsorption and their effects in osteoblastic behavior for bone tissue engineering

A novel synthetic method to synthesize hydroxyapatite/poly (D,L) lactic acid biocomposite is presented in this study by mixing only the precursors hydroxyapatite and (D,L) LA monomer without adding neither solvent nor catalyst. Three compositions were successfully synthesized with the weight ratios of 1/1, 1/3, and 3/5 (hydroxyapatite/(D,L) lactic acid), and the grafting efficiency of poly (D,L) lactic acid on hydroxyapatite surface reaches up to 84 %. Scanning electron microscopy and Fourier transform infrared spectroscopy showed that the hydroxyapatite particles were successfully incorporated into the poly (D,L) lactic acid polymer and X ray diffraction analysis showed that hydroxyapatite preserved its crystallinity after poly (D,L) lactic acid grafting. Differential scanning calorimetry shows that Tg of hydroxyapatite/poly (D,L) lactic acid composite is less than Tg of pure poly (D,L) lactic acid, which facilitates the shaping of the composite obtained. The addition of poly (D,L) lactic acid improves the adsorption properties of hydroxyapatite for fibronectin extracellular matrix protein. Furthermore, the presence of poly (D,L) lactic acid on hydroxyapatite surface coated with fibronectin enhanced pre-osteoblast STRO-1 adhesion and cell spreading. These results show the promising potential of hydroxyapatite/poly (D,L) lactic acid composite as a bone substitute material for orthopedic applications and bone tissue engineering.

Porous poly(L-lactic acid) sheet prepared by stretching with starch particles as filler for tissue engineering

Porous poly(L-lactic acid) (PLLA) sheets were prepared by uniaxial stretching PLLA sheets containing starch filler. Here, the starch filler content, stretching ratio, stretching rate and stretching temperature are important factors to influence the structure of the porous PLLA sheets, therefore, they have been investigated in detail. The pore size distribution and tortuosity were characterized by Mercury Intrusion Porosimetry. The results revealed that the porosity and pore size enlarged with the increase of the starch filler content and stretching ratio, while shrank with the rise of stretching temperature. On the other hand, the pore structure almost had no changes with the stretching rate ranging between 5 and 40 mm/min. In order to test and verify that the porous PLLA sheet was suitable for the tissue engineering, the starch particles were removed by selective enzymatic degradation and its in vitro biocompatibility to osteoblast-like MC3T3-E1 cells was investigated.

Biomedical Applications of Biodegradable Polyesters

The focus in the field of biomedical engineering has shifted in recent years to biodegradable polymers and, in particular, polyesters. Dozens of polyester-based medical devices are commercially available, and every year more are introduced to the market. The mechanical performance and wide range of biodegradation properties of this class of polymers allow for high degrees of selectivity for targeted clinical applications. Recent research endeavors to expand the application of polymers have been driven by a need to target the general hydrophobic nature of polyesters and their limited cell motif sites. This review provides a comprehensive investigation into advanced strategies to modify polyesters and their clinical potential for future biomedical applications.

Effect of chemical heterogeneity of biodegradable polymers on surface energy: A static contact angle analysis of polyester model films

Biodegradable and bioassimilable poly((R,S)-3,3 dimethylmalic acid) (PDMMLA) derivatives were synthesized and characterized in order to develop a new coating for coronary endoprosthesis enabling the reduction of restenosis. The PDMMLA was chemically modified to form different custom groups in its side chain. Three side groups were chosen: the hexyl group for its hydrophobic nature, the carboxylic acid and alcohol groups for their acid and neutral hydrophilic character, respectively. The sessile drop method was applied to characterize the wettability of biodegradable polymer film coatings. Surface energy and components were calculated. The van Oss approach helped reach not only the dispersive and polar acid-base components of surface energy but also acid and basic components. Surface topography was quantified by atomic force microscopy (AFM) and subnanometer average values of roughness (Ra) were obtained for all the analyzed surfaces. Thus, roughness was considered to have a negligible effect on wettability measurements. In contrast, heterogeneous surfaces had to be corrected by the Cassie-Baxter equation for copolymers (10/90, 20/80 and 30/70). The impact of this correction was quantified for all the wettability parameters. Very high relative corrections (%) were found, reaching 100% for energies and 30% for contact angles.

Development of a bone substitute material based on alpha-tricalcium phosphate scaffold coated with carbonate apatite/poly-epsilon-caprolactone

Interconnected porous tricalcium phosphate ceramics are considered to be potential bone substitutes. However, insufficient mechanical properties when using tricalcium phosphate powders remain a challenge. To mitigate these issues, we have developed a new approach to produce an interconnected alpha-tricalcium phosphate (α-TCP) scaffold and to perform surface modification on the scaffold with a composite layer, which consists of hybrid carbonate apatite / poly-epsilon-caprolactone (CO3Ap/PCL) with enhanced mechanical properties and biological performance. Different CO3Ap combinations were tested to evaluate the optimal mechanical strength and in vitro cell response of the scaffold. The α-TCP scaffold coated with CO3Ap/PCL maintained a fully interconnected structure with a porosity of 80% to 86% and achieved an improved compressive strength mimicking that of cancellous bone. The addition of CO3Ap coupled with the fully interconnected microstructure of the α-TCP scaffolds coated with CO3Ap/PCL increased cell attachment, accelerated proliferation and resulted in greater alkaline phosphatase (ALP) activity. Hence, our bone substitute exhibited promising potential for applications in cancellous bone-type replacement.

Microsphere-Based Scaffolds Carrying Opposing Gradients of Chondroitin Sulfate and Tricalcium Phosphate

Extracellular matrix (ECM) components, such as chondroitin sulfate (CS) and tricalcium phosphate, serve as raw materials, and thus spatial patterning of these raw materials may be leveraged to mimic the smooth transition of physical, chemical, and mechanical properties at the bone-cartilage interface. We hypothesized that encapsulation of opposing gradients of these raw materials in high molecular weight poly(d,l-lactic-co-glycolic acid) (PLGA) microsphere-based scaffolds would enhance differentiation of rat bone marrow-derived stromal cells. The raw material encapsulation altered the microstructure of the microspheres and also influenced the cellular morphology that depended on the type of material encapsulated. Moreover, the mechanical properties of the raw material encapsulating microsphere-based scaffolds initially relied on the composition of the scaffolds and later on were primarily governed by the degradation of the polymer phase and newly synthesized ECM by the seeded cells. Furthermore, raw materials had a mitogenic effect on the seeded cells and led to increased glycosaminoglycan (GAG), collagen, and calcium content. Interestingly, the initial effects of raw material encapsulation on a per-cell basis might have been overshadowed by medium-regulated environment that appeared to favor osteogenesis. However, it is to be noted that in vivo, differentiation of the cells would be governed by the surrounding native environment. Thus, the results of this study demonstrated the potential of the raw materials in facilitating neo-tissue synthesis in microsphere-based scaffolds and perhaps in combination with bioactive signals, these raw materials may be able to achieve intricate cell differentiation profiles required for regenerating the osteochondral interface.

Conidia of the insect pathogenic fungus, Metarhizium anisopliae, fail to adhere to mosquito larval cuticle

Adhesion of conidia of the insect pathogenic fungus, Metarhizium anisopliae, to the arthropod host cuticle initially involves hydrophobic forces followed by consolidation facilitated by the action of extracellular enzymes and secretion of mucilage. Gene expression analysis and atomic force microscopy were used to directly quantify recognition and adhesion between single conidia of M. anisopliae and the cuticle of the aquatic larval stage of Aedes aegypti and a representative terrestrial host, Tenebrio molitor. Gene expression data indicated recognition by the pathogen of both hosts; however, the forces for adhesion to the mosquito were approximately five times lower than those observed for Tenebrio. Although weak forces were recorded in response to Aedes, Metarhizium was unable to consolidate firm attachment. An analysis of the cuticular composition revealed an absence of long-chain hydrocarbons in Aedes larvae which are thought to be required for fungal development on host cuticle. This study provides, to our knowledge, the first evidence that Metarhizium does not form firm attachment to Ae. aegypti larvae in situ, therefore preventing the normal route of invasion and pathogenesis from occuring.