Fabrication of chitin-chitosan/nano ZrO(2) composite scaffolds for tissue engineering applications

Melt electrowriting of poly(ϵ-caprolactone)-poly(ethylene glycol) backbone polymer blend scaffolds with improved hydrophilicity and functionality

Melt electrowriting (MEW) is an additive manufacturing technique that harnesses electro-hydrodynamic phenomena to produce 3D-printed fibres with diameters on the scale of 10s of microns. The ability to print at this small scale provides opportunities to create structures with incredibly fine resolution and highly defined morphology. The current gold standard material for MEW is poly(ϵ-caprolactone) (PCL), a polymer with excellent biocompatibility but lacking in chemical groups that can allow intrinsic additional functionality. To provide this functionality while maintaining PCL's positive attributes, blending was performed with a Poly(Ethylene Glycol) (PEG)-based Acrylate endcapped Urethane-based Precursor (AUP). AUPs are a group of polymers, built on a backbone of existing polymers, which introduce additional functionality by the addition of one or more acrylate groups that terminate the polymer chain of a backbone polymer. By blending with a 20kDa AUP-PEG in small amounts, it is shown that MEW attributes are preserved, producing high-quality meshes. Blends were produced in various PCL:AUP weight ratios (100:0, 90:10 and 0:100) and processed into both solvent-cast films and MEW meshes that were used to characterise the properties of the blends. It was found that the addition of AUP-PEG to PCL significantly increases the hydrophilicity of structures produced with these polymers, and adds swelling capability compared to the non-swelling PCL. The developed blend (90:10) is shown to be processable using MEW, and the quality of manufactured scaffolds is evaluated against pure PCL scaffolds by performing scanning electron microscopy image analysis, with the quality of the novel MEW blend scaffolds showing comparable quality to that of pure PCL. The presence of the functionalisable AUP material on the surface of the developed scaffolds is also confirmed using fluorescence labelling of the acrylate groups. Biocompatibility of the MEW-processable blend was confirmed through a cell viability study, which found a high degree of cytocompatibility.

Fabrication and characterization of a bioactive composite scaffold based on polymeric collagen/gelatin/nano β-TCP for alveolar bone regeneration

One strategy to correct alveolar bone defects is use of bioactive bone substitutes to maintain the structure of defect site and facilitate cells and vessels' ingrowth. This study aimed to fabricate and characterize the freeze-dried bone regeneration scaffolds composed of polymeric Type I collagen, nano Beta-tricalcium phosphate (β-TCP), and gelatin. The stable structures of scaffolds were obtained by thermal crosslinking and EDC/NHS ((1-ethyl-3-(3-dimethylaminopropyl) carbodiimide)/(N-hydroxysuccinimide)) chemical crosslinking processes. Subsequently, the physicochemical and biological properties of the scaffolds were characterized and assessed. The results indicated the bioactive composite scaffolds containing 10% and 20% (w/v) nano β-TCP exhibited suitable porosity (84.45 ± 25.43 nm, and 94.51 ± 14.69 nm respectively), a rapid swelling property (reaching the maximum swelling rate at 1 h), excellent degradation resistance (residual mass percentage of scaffolds higher than 80% on day 90 in PBS and Type I collagenase solution respectively), and sustained calcium release capabilities. Moreover, they displayed outstanding biological properties, including superior cell viability, cell adhesion, and cell proliferation. Additionally, the scaffolds containing 10% and 20% (w/v) nano β-TCP could promote the osteogenic differentiation of MC3T3-E1. Therefore, the bioactive composite scaffolds containing 10% and 20% (w/v) nano β-TCP could be further studied for being used to treat alveolar bone defects in vivo.

Zirconia based composite scaffolds and their application in bone tissue engineering

In the field of bone tissue engineering, biomimetic scaffold utilization is deemed an immensely promising method. The bio-ceramic material Zirconia (ZrO2) has garnered significant attention in the biomimetic scaffolds realm due to its remarkable biocompatibility, superior mechanical strength, and exceptional chemical stability. Numerous examinations have been conducted to investigate the properties and functions of biomimetic structures built from zirconia. Generally, nano-ZrO2 materials have showcased encouraging applications in bone tissue engineering, providing a blend of mechanical robustness, bioactivity, drug delivery capabilities, and antibacterial properties. This review aims to concentrate on the properties and preparations of ZrO2 and its composite materials, while emphasizing its role along with other materials as scaffolds for bone tissue repair applications. The study also discusses the constraints of materials and technology involved in this domain. Ongoing research and development in this area are anticipated to further augment the potential of nano-ZrO2 for advancing bone regeneration therapies.

Recent Advances in the Production of Pharmaceuticals Using Selective Laser Sintering

Selective laser sintering (SLS) is an additive manufacturing process that has shown promise in the production of medical devices, including hip cups, knee trays, dental crowns, and hearing aids. SLS-based 3D-printed dosage forms have the potential to revolutionise the production of personalised drugs. The ability to manipulate the porosity of printed materials is a particularly exciting aspect of SLS. Porous tablet formulations produced by SLS can disintegrate orally within seconds, which is challenging to achieve with traditional methods. SLS also enables the creation of amorphous solid dispersions in a single step, rather than the multi-step process required with conventional methods. This review provides an overview of 3D printing, describes the operating mechanism and necessary materials for SLS, and highlights recent advances in SLS for biomedical and pharmaceutical applications. Furthermore, an in-depth comparison and contrast of various 3D printing technologies for their effectiveness in tissue engineering applications is also presented in this review.

Biomedical Applications of Zirconia-Based Nanomaterials: Challenges and Future Perspectives

ZrO₂ nanoparticles have received substantially increased attention in every field of life owing to their wide range of applications. Zirconium oxide is a commercially economical, non-hazardous, and sustainable metal oxide having diversified potential applications. ZrO₂ NPs play a vast role in the domain of medicine and pharmacy such as anticancer, antibacterial, and antioxidant agents and tissue engineering owing to their reliable curative biomedical applications. In this review article, we address all of the medical and biomedical applications of ZrO₂ NPs prepared through various approaches in a critical way. ZrO₂ is a bio-ceramic substance that has received increased attention in biomimetic scaffolds owing to its high mechanical strength, excellent biocompatibility, and high chemical stability. ZrO₂ NPs have demonstrated potential anticancer activity against various cancer cells. ZrO₂-based nanomaterials have exhibited potential antibacterial activity against various bacterial strains and have also demonstrated excellent antioxidant activity. The ZrO₂ nanocomposite also exhibits highly sensitive biosensing activity toward the sensing of glucose and other biological species.

Rapid Prototyping of 3D-Printed AgNPs- and Nano-TiO2-Embedded Hydrogels as Novel Devices with Multiresponsive Antimicrobial Capability in Wound Healing

Two antimicrobial agents such as silver nanoparticles (AgNPs) and titanium dioxide (TiO₂) have been formulated with natural polysaccharides (chitosan or alginate) to develop innovative inks for the rapid, customizable, and extremely accurate manufacturing of 3D-printed scaffolds useful as dressings in the treatment of infected skin wounds. Suitable chemical-physical properties for the applicability of these innovative devices were demonstrated through the evaluation of water content (88-93%), mechanical strength (Young's modulus 0.23-0.6 MPa), elasticity, and morphology. The antimicrobial tests performed against Staphylococcus aureus and Pseudomonas aeruginosa demonstrated the antimicrobial activities against Gram+ and Gram- bacteria of AgNPs and TiO₂ agents embedded in the chitosan (CH) or alginate (ALG) macroporous 3D hydrogels (AgNPs MIC starting from 5 µg/mL). The biocompatibility of chitosan was widely demonstrated using cell viability tests and was higher than that observed for alginate. Constructs containing AgNPs at 10 µg/mL concentration level did not significantly alter cell viability as well as the presence of titanium dioxide; cytotoxicity towards human fibroblasts was observed starting with an AgNPs concentration of 100 µg/mL. In conclusions, the 3D-printed dressings developed here are cheap, highly defined, easy to manufacture and further apply in personalized antimicrobial medicine applications.

Cell-based wound dressing: Bilayered PCL/gelatin nanofibers-alginate/collagen hydrogel scaffold loaded with mesenchymal stem cells

Wound dressing is applied to promote the healing process, wound protection, and additionally regeneration of injured skin. In this study, a bilayer scaffold composed of a hydrogel and nanofibers was fabricated to improve the regeneration of injured skin. To this end, polycaprolactone/gelatin (PCL/Gel) nanofibers were electrospun directly on the prepared collagen/alginate (Col/Alg) hydrogel. The bilayer scaffold was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), mechanical properties, and swelling/degradation time. Cytotoxicity assays were evaluated using MTT assay. Then, the nanofiber and bilayer scaffolds were seeded with Adipose-derived stem cells (ADSCs). ADSCs were isolated from rat adipose tissue and analyzed using flow cytometry, in advance. Full-thickness wounds on the backs of rats were dressed with ADSCs-seeded bilayer scaffolds and nanofibers. Histopathological evaluations were performed after 14 and 21 days using H&E (hematoxylin and eosin) staining. The results indicated that re-epithelialization, angiogenesis, and collagen remodeling were enhanced in ADSCs-seeded bilayer scaffolds and nanofibers in comparison with the control group. In conclusion, the best re-epithelialization, collagen organization, neovascularization, and low presence of inflammation in the wound area were observed in the ADSCs-seeded bilayer scaffolds.

Antioxidant, antibacterial, and anti-inflammatory Periplaneta americana remnant chitosan/polysaccharide composite film: In vivo wound healing application evaluation

Periplaneta americana (P. americana), which is widely used for wound healing in China, produces a large amount of solid waste (P. americana remnant) after pharmaceutical production extraction. P. americana remnant chitosan (PAC) has a low molecular weight, low crystallinity, and easily modifiable structural properties. In this study, PAC and P. americana remnant polysaccharide (PAP) were used as raw materials to prepare a composite film (PAPCF). The good biocompatibility of the composite film was verified by cell proliferation assays and protein adsorption assays. The bioactivity of the composite film was assessed by antibacterial and in vivo/vitro antioxidant assays to evaluate its potential as a wound dressing. The wound healing experiment revealed that PAPCF improved wound closure and collagen deposition, decreased reactive oxygen species levels, and attenuated the inflammatory response, enabling rapid wound healing from the inflammatory phase to the proliferative phase in mice. Additionally, PAPCF was administered only once, reducing the chance of infection from multiple deliveries. In summary, this paper presents an easy-to-administer, cost-effective, and effective dressing candidate for wound treatment based on the environmental concept of resource reuse.

Biomimetic development of chitosan and sodium alginate-based nanocomposites contains zirconia for tissue engineering applications

Nanostructured materials possess unique structural and functional properties that play a crucial position in tissue engineering applications. Present investigation is aimed to synthesize chitosan-sodium alginate (CS) nanocomposite using hydrothermally prepared zirconia nanoparticles. In this, three different weight percentages of (0.5, 1, and 1.5) zirconia nanoparticles are utilized for the preparation of biomimetic nanocomposite scaffolds (CSZ) employing 4 wt% of CS by a solvent casting technique. Physico-chemical and thermal behavior of the prepared nanoparticles and their CSZ scaffolds are comprehensively characterized. Bioactivity of the prepared zirconia nanoparticles and CSZ scaffolds are explored in terms of in vitro biocompatibility, protein absorption in simulated body fluid (SBF), and phosphate buffered saline (PBS). Agar disc diffusion method is employed to identify the antibacterial property against Staphylococcus aureus and Escherichia coli. In vitro cytotoxicity of zirconia nanoparticles and CSZ scaffolds is identified against human urothelial carcinoma (UC6) and osteosarcoma (MG-63) cells. These studies explore that zirconia nanoparticles are suitable for biomedical applications while it is interacted with chitosan and sodium alginate (CS) due to their promising biocompatibility. Biomimetically obtained chitosan/sodium alginate scaffold contain 1 wt% zirconia nanoparticles show higher biocompatibility amenable for tissue engineering applications.

Biomedical applications of carbohydrate-based polyurethane: From biosynthesis to degradation

The foremost common natural polymers are carbohydrate-based polymers or polysaccharides, having a long chain of monosaccharide or disaccharide units linked together via a glycosidic linkage to form a complex structure. There are several uses of carbohydrate-based polymers in biomedical sector due to its attractive features including less toxicity, biocompatibility, biodegradability, high reactivity, availability, and relatively inexpensive. The aim of our study was to explore the synthetic approaches for the preparation of numerous carbohydrate-based polyurethanes (PUs) and their wide range of pharmaceutical and biomedical applications. The data summarized in this study shows that the addition of carbohydrates in the structural skeleton of PUs not only improve their suitability but also effect the applicability for employing them in biological applications. Carbohydrate-based units are incorporated into the PUs, which is the most convenient method for the synthesis of novel biocompatible and biodegradable carbohydrate-based PUs to use in various biomedical applications.

Novel chitosan-poly(vinyl acetate) biomaterial suitable for additive manufacturing and bone tissue engineering applications

Chitosan, a biocompatible and biodegradable natural polymer, offers great promise as a biomaterial for tissue engineering applications. Chitosan scaffolds have previously been fabricated using additive manufacturing techniques, however, the use of crosslinkers, weak mechanical stability and structural resolution remain problematic. In this study Chitosan-PVAc biopolymer blends were prepared using a non-organic solvent that can prepare a three-dimensional printable biopolymer in less time than conventional methods. Prepared films were characterised using SEM, FTIR and thermogravimetric analysis. Additionally, the swelling properties, biodegradability and printability of the scaffolds were also studied. The fabricated films were biodegradable within a 3-week period and showed controllable swelling properties. Results indicated no toxicity and cells attached onto films. Additionally, hydrogels showed antibacterial activity against S. aureus, S. epidermidis and E.coli, which could potentially prevent implant related infections. Additive manufacturing simulation of PVAc composite 3% chitosan and PVAc composite 4% chitosan were able to produce a layered scaffold without using crosslinkers and therefore confirming printability. Cytocompabability were assessed using a resazurin assay and cell attachment. From these results, we concluded that the printable PVAc composite 3% chitosan and PVAc composite 4% chitosan biopolymer blends meet the requirements of a biomaterial and can potentially be used for biomedical implants.

Three-Dimensional Zirconia-Based Scaffolds for Load-Bearing Bone-Regeneration Applications: Prospects and Challenges

The design of zirconia-based scaffolds using conventional techniques for bone-regeneration applications has been studied extensively. Similar to dental applications, the use of three-dimensional (3D) zirconia-based ceramics for bone tissue engineering (BTE) has recently attracted considerable attention because of their high mechanical strength and biocompatibility. However, techniques to fabricate zirconia-based scaffolds for bone regeneration are in a stage of infancy. Hence, the biological activities of zirconia-based ceramics for bone-regeneration applications have not been fully investigated, in contrast to the well-established calcium phosphate-based ceramics for bone-regeneration applications. This paper outlines recent research developments and challenges concerning numerous three-dimensional (3D) zirconia-based scaffolds and reviews the associated fundamental fabrication techniques, key 3D fabrication developments and practical encounters to identify the optimal 3D fabrication technique for obtaining 3D zirconia-based scaffolds suitable for real-world applications. This review mainly summarized the articles that focused on in vitro and in vivo studies along with the fundamental mechanical characterizations on the 3D zirconia-based scaffolds.

Effect of Chitosan/Nano-TiO2 Composite Coating on the Postharvest Quality of Blueberry Fruit

Blueberries are a rich source of health-promoting compounds such as vitamins and anthocyanins and show a high antioxidant capacity. Thus, considerable commercial and scientific interest exists in prolonging its postharvest life to meet the year-round demand for this fruit. In this investigation, the effect of a chitosan-based edible coating, as well as a chitosan-based edible coating containing nanosized titanium dioxide particles (CTS-TiO2), on the postharvest quality of blueberry fruit quality was evaluated during storage at 0 °C. The blueberries were treated with a chitosan coating (CTS) and a CTS-TiO2 composite, respectively. The most suitable chitosan and nano-TiO2 fraction concentrations to be incorporated in the coating formulation were prepared based on the wettability of the corresponding coating solutions. Changes in firmness, total soluble solids (TSS), titratable acidity (TA), ascorbic acid (VC), malondialdehyde (MDA), polyphenol oxidase (PPO), and peroxidase (POD) activities, anthocyanins, flavonoids, total phenolic content, and microbiological analysis were measured and compared. This combined treatment prevented product corruption. Compared with CTS, the CTS-TiO2 composite coating application effectively slowed down the decrease in firmness, TSS, VC, and TA in the blueberries. Additionally, changes in the total polyphenol, anthocyanin, and flavonoid contents and the antioxidant capacity of CTS-TiO2 composite coating blueberry fruits were delayed. Therefore, these results indicated that the chitosan/nano-TiO2 composite coating could maintain the nutrient composition of blueberries while playing a significant role in preserving the quality of fruit at 0 °C.

Changing the morphology of one-dimensional titanate nanostructures affects its tissue distribution and toxicity

The present research investigated the impact of the morphology change of titanate (TiO₂) nanostructures on its tissue distribution and toxicity. The TiO₂ nanotubes, rods, and ribbons were synthesized by the hydrothermal technique, and the morphology was adjusted by alteration of the hydrothermal duration time. The characterization techniques were X-ray diffraction, high-resolution transmission electron microscopy, dynamic light scattering, and the Brunauer-Emmett-Teller method for measuring the surface area. The intravenously administrated dose (5 mg/kg) was injected as a single dose for 1 day and consecutively for 42 days. The quantitative analysis of accumulated TiO₂ nanostructures in the liver, spleen, and the heart was performed using an inductively coupled plasma emission spectrometer, and the organs' toxicity was estimated by histopathological analysis. The prepared nanostructures exhibited differences in morphology, crystallinity, size distribution, surface area, zeta potential, and aspect ratio. The results revealed a tissue distribution difference between the liver, spleen, and heart of these nanostructures, the distribution order was the liver, spleen, and the heart for all TiO₂ nanostructures. The toxicity was induced with different degrees. The nanotubes were the most harmful among the three formats. In summary, changes in the morphology of the TiO₂ nanostructures change its distribution and toxicity.

Novel hybrid polyester-polyacrylate hydrogels enriched with platelet-derived growth factor for chondrogenic differentiation of adipose-derived mesenchymal stem cells in vitro

Background

The goal of the present study was to create a new biodegradable hybrid PCL-P (HEMA-NIPAAm) thermosensitive hydrogel scaffold by grafting PNIPAAm-based copolymers with biodegradable polyesters to promote the chondrogenic differentiation of human progenitor cells (adipose-derived stem cells-hASCs) in the presence of the platelet-derived growth factor (PDGF-BB). Different mixture ratios including 50 mmol ε-caprolactone and 10 mmol HEMA (S-1), 30 mmol ε-caprolactone and 10 mmol HEMA (S-2), 10 mmol ε-caprolactone and 30 mmol HEMA (S-3) were copolymerized followed by the addition of NIPAAm.

Results

A mild to moderate swelling and wettability rates were found in S-2 group copmpared to the S-1 ans S-3 samples. After 7 weeks, S-2 degradation rate reached ~ 43.78%. According to the LCST values, S-2, reaching 37 °C, was selected for different in vitro assays. SEM imaging showed nanoparticulate structure of the scaffold with particle size dimensions of about 62–85 nm. Compressive strength, Young’s modulus, and compressive strain (%) of S-2 were 44.8 MPa, 0.7 MPa, and 75.5%. An evaluation of total proteins showed that the scaffold had the potential to gradually release PDGF-BB. When hASCs were cultured on PCL-P (HEMA-NIPAAm) in the presence of PDGF-BB, the cells effectively attached and flattened on the scaffold surface for a period of at least 14 days, the longest time point evaluated, with increased cell viability rates as measured by performing an MTT assay (p < 0.05). Finally, a real-time RT-PCR analysis demonstrated that the combination of PCL-P (HEMA-NIPAAm) and PDGF-BB promoted the chondrogenesis of hASCs over a period of 14 days by up-regulating the expression of aggrecan, type-II collagen, SOX9, and integrin β1 compared with the non-treated control group (p < 0.05).

Conclusion

These results demonstrate that the PCL-P(HEMA-NIPAAm) hydrogel scaffold carrying PDGF-BB as a matrix for hASC cell seeding is a valuable system that may be used in the future as a three-dimensional construct for implantation in cartilage injuries.

Comprehensive Survey on Nanobiomaterials for Bone Tissue Engineering Applications

One of the most important ideas ever produced by the application of materials science to the medical field is the notion of biomaterials. The nanostructured biomaterials play a crucial role in the development of new treatment strategies including not only the replacement of tissues and organs, but also repair and regeneration. They are designed to interact with damaged or injured tissues to induce regeneration, or as a forest for the production of laboratory tissues, so they must be micro-environmentally sensitive. The existing materials have many limitations, including impaired cell attachment, proliferation, and toxicity. Nanotechnology may open new avenues to bone tissue engineering by forming new assemblies similar in size and shape to the existing hierarchical bone structure. Organic and inorganic nanobiomaterials are increasingly used for bone tissue engineering applications because they may allow to overcome some of the current restrictions entailed by bone regeneration methods. This review covers the applications of different organic and inorganic nanobiomaterials in the field of hard tissue engineering.

Vapor-Deposited Biointerfaces and Bacteria: An Evolving Conversation

At the biointerface where materials and microorganisms meet, the organic and synthetic worlds merge into a new science that directs the design and safe use of synthetic materials for biological applications. Vapor deposition techniques provide an effective way to control the material properties of these biointerfaces with molecular-level precision that is important for biomaterials to interface with bacteria. In recent years, biointerface research that focuses on bacteria-surface interactions has been primarily driven by the goals of killing bacteria (antimicrobial) and fouling prevention (antifouling). Nevertheless, vapor deposition techniques have the potential to create biointerfaces with features that can manipulate and dictate the behavior of bacteria rather than killing or deterring them. In this review, we focus on recent advances in antimicrobial and antifouling biointerfaces produced through vapor deposition and provide an outlook on opportunities to capitalize on the features of these techniques to find unexplored connections between surface features and microbial behavior.

Preparation of Gelatin and Gelatin/Hyaluronic Acid Cryogel Scaffolds for the 3D Culture of Mesothelial Cells and Mesothelium Tissue Regeneration

Mesothelial cells are specific epithelial cells that are lined in the serosal cavity and internal organs. Nonetheless, few studies have explored the possibility to culture mesothelial cells in a three-dimensional (3D) scaffold for tissue engineering applications. Towards this end, we fabricated macroporous scaffolds from gelatin and gelatin/hyaluronic acid (HA) by cryogelation, and elucidated the influence of HA on cryogel properties and the cellular phenotype of mesothelial cells cultured within the 3D scaffolds. The incorporation of HA was found not to significantly change the pore size, porosity, water uptake kinetics, and swelling ratios of the cryogel scaffolds, but led to a faster scaffold degradation in the collagenase solution. Adding 5% HA in the composite cryogels also decreased the ultimate compressive stress (strain) and toughness of the scaffold, but enhanced the elastic modulus. From the in vitro cell culture, rat mesothelial cells showed quantitative cell viability in gelatin (G) and gelatin/HA (GH) cryogels. Nonetheless, mesothelial cells cultured in GH cryogels showed a change in the cell morphology and cytoskeleton arrangement, reduced cell proliferation rate, and downregulation of the mesothelium specific maker gene expression. The production of key mesothelium proteins E-cadherin and calretinin were also reduced in the GH cryogels. Choosing the best G cryogels for in vivo studies, the cell/cryogel construct was used for the transplantation of allograft mesothelial cells for mesothelium reconstruction in rats. A mesothelium layer similar to the native mesothelium tissue could be obtained 21 days post-implantation, based on hematoxylin and eosin (H&E) and immunohistochemical staining.

Application of Chitosan in Bone and Dental Engineering

Chitosan is a deacetylated polysaccharide from chitin, the natural biopolymer primarily found in shells of marine crustaceans and fungi cell walls. Upon deacetylation, the protonation of free amino groups of the d-glucosamine residues of chitosan turns it into a polycation, which can easily interact with DNA, proteins, lipids, or negatively charged synthetic polymers. This positive-charged characteristic of chitosan not only increases its solubility, biodegradability, and biocompatibility, but also directly contributes to the muco-adhesion, hemostasis, and antimicrobial properties of chitosan. Combined with its low-cost and economic nature, chitosan has been extensively studied and widely used in biopharmaceutical and biomedical applications for several decades. In this review, we summarize the current chitosan-based applications for bone and dental engineering. Combining chitosan-based scaffolds with other nature or synthetic polymers and biomaterials induces their mechanical properties and bioactivities, as well as promoting osteogenesis. Incorporating the bioactive molecules into these biocomposite scaffolds accelerates new bone regeneration and enhances neovascularization in vivo.

Additive manufacturing of photo-crosslinked gelatin scaffolds for adipose tissue engineering

There exists a clear clinical need for adipose tissue reconstruction strategies to repair soft tissue defects which outperform the currently available approaches. In this respect, additive manufacturing has shown to be a promising alternative for the development of larger constructs able to support adipose tissue engineering. In the present work, a thiol-ene photo-click crosslinkable gelatin hydrogel was developed which allowed extrusion-based additive manufacturing into porous scaffolds. To this end, norbornene-functionalized gelatin (Gel-NB) was combined with thiolated gelatin (Gel-SH). The application of a macromolecular gelatin-based thiolated crosslinker holds several advantages over conventional crosslinkers including cell-interactivity, less chance at phase separation between scaffold material and crosslinker and the formation of a more homogeneous network. Throughout the paper, these photo-click scaffolds were benchmarked to the conventional methacrylamide-modified gelatin (Gel-MA). The results indicated that stable scaffolds could be realized which were further characterized physico-chemically by performing swelling, mechanical and in vitro biodegradability assays. Furthermore, the seeded adipose tissue-derived stem cells (ASCs) remained viable (>90%) up to 14 days and were able to proliferate. In addition, the cells could be differentiated into the adipogenic lineage on the photo-click crosslinked scaffolds, thereby performing better than the cells supported by the frequently reported Gel-MA scaffolds. As a result, the developed photo-click crosslinked scaffolds can be considered a promising candidate towards adipose tissue engineering and a valuable alternative for the omnipresent Gel-MA. STATEMENT OF SIGNIFICANCE: The field of adipose tissue engineering has emerged as a promising strategy to repair soft tissue defects. Herein, Gel-NB/Gel-SH gelatin-based hydrogel scaffolds were produced using extrusion-based additive manufacturing. Using a cell-interactive, thiolated gelatin crosslinker, a homogeneous network was formed and the risk of phase separation between norbornene-modified gelatin and macromolecular crosslinkers was reduced. UV-induced crosslinking of these materials is based on step growth polymerization which requires less free radicals to enable polymerization. Our results demonstrated the potential of the developed scaffolds, due to their favourable physico-chemical characteristics as well as their adipogenic differentiation potential when benchmarked to Gel-MA scaffolds. Hence, the hydrogels could be of great interest towards future development of adipose tissue constructs and tissue engineering in general.

Femtosecond Laser Fabrication of Engineered Functional Surfaces Based on Biodegradable Polymer and Biopolymer/Ceramic Composite Thin Films

Surface functionalization introduced by precisely-defined surface structures depended on the surface texture and quality. Laser treatment is an advanced, non-contact technique for improving the biomaterials surface characteristics. In this study, femtosecond laser modification was applied to fabricate diverse structures on biodegradable polymer thin films and their ceramic blends. The influences of key laser processing parameters like laser energy and a number of applied laser pulses (N) over laser-treated surfaces were investigated. The modification of surface roughness was determined by atomic force microscopy (AFM). The surface roughness (R_rms) increased from approximately 0.5 to nearly 3 µm. The roughness changed with increasing laser energy and a number of applied laser pulses (N). The induced morphologies with different laser parameters were compared via Scanning electron microscopy (SEM) and confocal microscopy analysis. The chemical composition of exposed surfaces was examined by FTIR, X-ray photoelectron spectroscopy (XPS), and XRD analysis. This work illustrates the capacity of the laser microstructuring method for surface functionalization with possible applications in improvement of cellular attachment and orientation. Cells exhibited an extended shape along laser-modified surface zones compared to non-structured areas and demonstrated parallel alignment to the created structures. We examined laser-material interaction, microstructural outgrowth, and surface-treatment effect. By comparing the experimental results, it can be summarized that considerable processing quality can be obtained with femtosecond laser structuring.

Fabrication and characterization of novel ethyl cellulose-grafted-poly (ɛ-caprolactone)/alginate nanofibrous/macroporous scaffolds incorporated with nano-hydroxyapatite for bone tissue engineering

The major challenge of tissue regeneration is to develop three dimensional scaffolds with suitable properties which would mimic the natural extracellular matrix to induce the adhesion, proliferation, and differentiation of cells. Several materials have been used for the preparation of the scaffolds for bone regeneration. In this study, novel ethyl cellulose-grafted-poly (ɛ-caprolactone) (EC-g-PCL)/alginate scaffolds with different contents of nano-hydroxyapatite were prepared by combining electrospinning and freeze-drying methods in order to provide nanofibrous/macroporous structures with good mechanical properties. For this aim, EC-g-PCL nanofibers were obtained with electrospinning, embedded layer-by-layer in alginate solutions containing nano-hydroxyapatite particles, and finally, these constructions were freeze-dried. The scaffolds possess highly porous structures with interconnected pore network. The swelling, porosity, and degradation characteristics of the EC-g-PCL/alginate scaffolds were decreased with the increase in nano-hydroxyapatite contents, whereas increases in the in-vitro biomineralization and mechanical strength were observed as the nano-hydroxyapatite content was increased. The cell response to EC-g-PCL/alginate scaffolds with/or without nano-hydroxyapatite was investigated using human dental pulp stem cells (hDPSCs). hDPSCs displayed a high adhesion, proliferation, and differentiation on nano-hydroxyapatite-incorporated EC-g-PCL/alginate scaffolds compared to pristine EC-g-PCL/alginate scaffold. Overall, these results suggested that the EC-g-PCL/alginate-HA scaffolds might have potential applications in bone tissue engineering.

Chitin/silk fibroin/TiO2 bio-nanocomposite as a biocompatible wound dressing bandage with strong antimicrobial activity

Interconnected microporous biodegradable and biocompatible chitin/silk fibroin/TiO₂ nanocomposite wound dressing with high antibacterial, blood clotting and mechanical strength properties were synthesized using freeze-drying method. The prepared nanocomposite dressings were characterized using SEM, FTIR, and XRD analysis. The prepared nanocomposite dressings showed high porosity above 90% with well-defined interconnected porous construction. Swelling and water uptake of the dressing were 93%, which is great for wound dressing applications. Haemostatic potential of the prepared dressings was studied and the results proved the higher blood clotting ability of the nanocomposites compared to pure components and commercially available products. Besides, cell viability, attachment and proliferation by MTT assay and DAPI staining on HFFF2 cell as a Human Caucasian Foetal Foreskin Fibroblast proved the cytocompatibility nature of the nanocomposite scaffolds with well improved proliferation and cell attachment. To determine the antimicrobial efficiencies, both disc diffusion method and colony counts were performed and results imply that nanocomposite scaffolds have high antimicrobial activity and could successfully inhibit the growth of E. coli, S. aureus, and C. albicans. Moreover, based on these results, the prepared chitin/silk fibroin/TiO₂ nanocomposite dressing could serve as a kind of promising wound dressing with great antibacterial and antifungal properties.

Fabrication and evaluation of 3D printed BCP scaffolds reinforced with ZrO2 for bone tissue applications

Fused deposition modeling (FDM) is a promising 3D printing and manufacturing step to create well interconnected porous scaffold designs from the computer-aided design (CAD) models for the next generation of bone scaffolds. The purpose of this study was to fabricate and evaluate a new biphasic calcium phosphate (BCP) scaffold reinforced with zirconia (ZrO₂ ) by a FDM system for bone tissue engineering. The 3D slurry foams with blending agents were successfully fabricated by a FDM system. Blending materials were then removed after the sintering process at high temperature to obtain a targeted BCP/ZrO₂ scaffold with the desired pore characteristics, porosity, and dimension. Morphology of the sintered scaffold was investigated with SEM/EDS mapping. A cell proliferation test was carried out and evaluated with osteosarcoma MG-63 cells. Mechanical testing and cell proliferation evaluation demonstrated that 90% BCP and 10% ZrO₂ scaffold had a significant effect on the mechanical properties maintaining a structure compared that of only 100% BCP with no ZrO₂ . Additionally, differentiation studies of human mesenchymal stem cells (hMSCs) on BCP/ZrO₂ scaffolds in static and dynamic culture conditions showed increased expression of bone morphogenic protein-2 (BMP-2) when cultured on BCP/ZrO₂ scaffolds under dynamic conditions compared to on BCP control scaffolds. The manufacturing of BCP/ZrO₂ scaffolds through this innovative technique of a FDM may provide applications for various types of tissue regeneration, including bone and cartilage.

Methacrylated gelatin/hyaluronan-based hydrogels for soft tissue engineering

In vitro–generated soft tissue could provide alternate therapies for soft tissue defects. The aim of this study was to evaluate methacrylated gelatin/hyaluronan as scaffolds for soft tissue engineering and their interaction with human adipose–derived stem cells (hASCs). ASCs were incorporated into methacrylated gelatin/hyaluronan hydrogels. The gels were photocrosslinked with a lithium phenyl-2,4,6-trimethylbenzoylphosphinate photoinitiator and analyzed for cell viability and adipogenic differentiation of ASCs over a period of 30 days. Additionally, an angiogenesis assay was performed to assess their angiogenic potential. After 24 h, ASCs showed increased viability on composite hydrogels. These results were consistent over 21 days of culture. By induction of adipogenic differentiation, the mature adipocytes were observed after 7 days of culture, their number significantly increased until day 28 as well as expression of fatty acid binding protein 4 and adiponectin. Our scaffolds are promising as building blocks for adipose tissue engineering and allowed long viability, proliferation, and differentiation of ASCs.

Natural and synthetic polymers/bioceramics/bioactive compounds-mediated cell signalling in bone tissue engineering

Bone is a highly integrative and dynamic tissue of the human body. It is continually remodeled by bone cells such as osteoblasts, osteoclasts. When a fraction of a bone is damaged or deformed, stem cells and bone cells under the influence of several signaling pathways regulate bone regeneration at the particular locale. Effective therapies for bone defects can be met via bone tissue engineering which employs drug delivery systems with biomaterials to enhance cellular functions by acting on signaling pathways such as Wnt, BMP, TGF-β, and Notch. This review provides the current understanding of polymers/bioceramics/bioactive compounds as scaffolds in activation of signaling pathways for the formation of bone.

Synthesis and properties of poly(DEX-GMA/AAc) microgel particle as a hemostatic agent

Poly(DEX-GMA/AAc) microgel particles were designed for the staunching of bleeding through absorption of water in blood and forming a gelled film as a barrier.

In situ synthesised TiO2-chitosan-chondroitin 4-sulphate nanocomposites for bone implant applications

The artificial materials for bone implant applications are gaining more importance in the recent years. The series titania-chitosan-chondroitin 4-sulphate nanocomposites of three different concentrations (2:1:x, where x- 0.125, 0.25, 0.5) have been synthesised by in situ sol-gel method and characterised by various techniques. The particle size of the nanocomposites ranges from 30-50 nm. The bioactivity, swelling nature, and the antimicrobial nature of the nanocomposites were investigated. The swelling ability and bioactivity of the composites is significantly greater and they possess high zone of inhibition against the microorganisms such as Staphylococcus aureus and Escherichia coli. The cell viability of the nanocomposites were evaluated by using MG-63 and observed the composites possess high cell viability at low concentration. The excellent bioactivity and biocompatibility makes these nanocomposites a promising biomaterial for bone implant applications.

An overview of chitin or chitosan/nano ceramic composite scaffolds for bone tissue engineering

Chitin and chitosan based nanocomposite scaffolds have been widely used for bone tissue engineering. These chitin and chitosan based scaffolds were reinforced with nanocomponents viz Hydroxyapatite (HAp), Bioglass ceramic (BGC), Silicon dioxide (SiO₂), Titanium dioxide (TiO₂) and Zirconium oxide (ZrO₂) to develop nanocomposite scaffolds. Plenty of works have been reported on the applications and characteristics of the nanoceramic composites however, compiling the work done in this field and presenting it in a single article is a thrust area. This review is written with an aim to fill this gap and focus on the preparations and applications of chitin or chitosan/nHAp, chitin or chitosan/nBGC, chitin or chitosan/nSiO₂, chitin or chitosan/nTiO₂ and chitin or chitosan/nZrO₂ in the field of bone tissue engineering in detail. Many reports so far exemplify the importance of ceramics in bone regeneration. The effect of nanoceramics over native ceramics in developing composites, its role in osteogenesis etc. are the gist of this review.

Investigation of synergistic effects of inductive and conductive factors in gelatin-based cryogels for bone tissue engineering

Macroporous and biocompatible scaffolds for bone tissue engineering were prepared from 4% gelatin (G) and 4% gelatin/2% nanohydroxyapatite (nHAP), (GN), by cryogelation. The cryogels have interconnected pores with pore size around 100 μm and a high degree of cross-linking. The incorporation of nHAP slightly reduced the porosity, degree of crosslinking, swelling kinetics and equilibrium water uptake, but enhanced the toughness of the cryogel scaffolds. The osteo-regeneration potential of GN cryogels was further enhanced by binding with bone morphogenetic protein (BMP-2) to produce the gelatin/nHAP/BMP-2 (GNB) scaffold. The efficacy of BMP-2 incorporation was tested through in vitro release studies and a sustained release profile could be observed from the cumulative BMP-2 release curve. To elucidate the effect of cryogel composition on cell proliferation and differentiation, rabbit adipose-derived stem cells (ADSCs) were seeded in cryogel scaffolds. In vitro studies demonstrated a reduced proliferation rate and enhanced osteogenic differentiation of ADSCs in GNB cryogel scaffolds from the combined effect of nHAP and BMP-2, judging from the elevated alkaline phosphatase activity and the degree of mineralization. Confocal microscopy confirmed high viability and good cytoskeletal spreading of ADSCs on cryogels while osteocalcin (OCN) protein quantification affirmed the dominance of GNB in the osteogenic differentiation of ADSCs compared to G and GN cryogels. The maximum osteogenesis capability of GNB was also confirmed through the up-regulation of specific bone maker genes of early marker protein collagen I (COL I) and late marker protein osteopontin (OPN). From an in vivo animal model, computed tomography analysis confirmed the superior bone regeneration capability of ADSCs in GNB cryogels by implanting ADSCs/GNB cryogel constructs in rabbit calvarial critical size defects. Histological and immunohistochemical analysis demonstrated new bone formation and continued expression of COL I and OCN bone-specific proteins at the defect site. Taken together, the results demonstrate that G cryogels modified with osteo-conductive nHAP and osteo-inductive BMP-2 could provide cues to synergistically promote the osteogenesis of ADSCs in vitro and in vivo.

Chitosan based biocomposite scaffolds for bone tissue engineering

The clinical demand for scaffolds and the diversity of available polymers provide freedom in the fabrication of scaffolds to achieve successful progress in bone tissue engineering (BTE). Chitosan (CS) has drawn much of the attention in recent years for its use as graft material either as alone or in a combination with other materials in BTE. The scaffolds should possess a number of properties like porosity, biocompatibility, water retention, protein adsorption, mechanical strength, biomineralization and biodegradability suited for BTE applications. In this review, CS and its properties, and the role of CS along with other polymeric and ceramic materials as scaffolds for bone tissue repair applications are highlighted.

Antibacterial properties of Cu–ZrO2thin films prepared via aerosol assisted chemical vapour deposition

The antibacterial properties of a Cu–ZrO₂film grownviaaerosol assisted chemical vapour deposition are presented.