Enhancing proliferation and osteogenic differentiation of HMSCs on casein/chitosan multilayer films

Casein-based conjugates and graft copolymers. Synthesis, properties, and applications

Biobased natural polymers, including polymers of natural origin such as casein, are growing rapidly in the light of the environmental pollution caused by many mass-produced commercial synthetic polymers. Although casein has interesting intrinsic properties, especially for the food industry, numerous chemical reactions have been carried out to broaden the range of its properties, most of them preserving casein's nontoxicity and biodegradability. New conjugates and graft copolymers have been developed especially by Maillard reaction of the amine functions of the casein backbone with the aldehyde functions of sugars, polysaccharides, or other molecules. Carried out with dialdehydes, these reactions lead to the cross-linking of casein giving three-dimensional polymers. Acylation and polymerization of various monomers initiated by amine functions are also described. Other reactions, far less numerous, involve alcohol and carboxylic acid functions in casein. This review provides an overview of casein-based conjugates and graft copolymers, their properties, and potential applications.

Wet-Spun Chitosan-Sodium Caseinate Fibers for Biomedicine: From Spinning Process to Physical Properties

We designed and characterized chitosan-caseinate fibers processed through wet spinning for biomedical applications such as drug delivery from knitted medical devices. Sodium caseinate was either incorporated directly into the chitosan dope or allowed to diffuse into the chitosan hydrogel from a coagulation bath containing sodium caseinate and sodium hydroxide (NaOH). The latter route, where caseinate was incorporated in the neutralization bath, produced fibers with better mechanical properties for textile applications than those formed by the chitosan-caseinate mixed collodion route. The latter processing method consists of enriching a pre-formed chitosan hydrogel with caseinate, preserving the structure of the semicrystalline hydrogel without drastically affecting interactions involved in the chitosan self-assembly. Thus, dried fibers, after coagulation in a NaOH/sodium caseinate aqueous bath, exhibited preserved ultimate mechanical properties. The crystallinity ratio of chitosan was not significantly impacted by the presence of caseinate. However, when caseinate was incorporated into the chitosan dope, chitosan-caseinate fibers exhibited lower ultimate mechanical properties, possibly due to a lower entanglement density in the amorphous phase of the chitosan matrix. A standpoint is to optimize the chitosan-caseinate composition ratio and processing route to find a good compromise between the preservation of fiber mechanical properties and appropriate fiber composition for potential application in drug release.

Surface-modified titanium and titanium-based alloys for improved osteogenesis: A critical review

As implantable materials, titanium, and its alloys have garnered enormous interest from researchers for dental and orthopedic procedures. Despite their success in wide clinical applications, titanium, and its alloys fail to stimulate osteogenesis, resulting in poor bonding strength with surrounding bone tissue. Optimizing the surface topology and altered compositions of titanium and titanium-based alloys substantially promotes peri-implant bone regeneration. This review summarizes the utilization and importance of various osteogenesis components loaded onto titanium and its alloys. Further, different surface-modification methods and the release efficacy of loaded substances are emphasized. Finally, we summarize the article with prospects. We believe that further investigation studies must focus on identifying novel loading components, exploring various innovative, optimized surface-modification methods, and developing a sustained-release system on implant surfaces to improve peri-implant bone formation.

Casein-assisted exfoliation of tungsten disulfide nanosheets for biomedical applications

Our regular life can be more challenging by bone abnormalities. Bone tissue engineering is used for repairing, regenerating, or replacing bone tissue that has been injured or infected. It is effective in overcoming the drawbacks of conventional bone grafting methods like autograft and allograft by enhancing the effectiveness of bone regeneration. Recent discoveries have shown that the exfoliation of transition metal dichalcogenides (TMDs) with protein is in great demand for bone tissue engineering applications. WS2 nanosheets were developed using casein and subsequently characterized with different analytical techniques. Strong absorption peaks were observed in the UV-visible spectra at 520 nm and 630 nm. Alginate and alginate-casein WS2 microspheres were developed. Stereomicroscopic images of the microspheres are spherical in shape and have an average diameter of around 0.8 ± 0.2 mm. The alginate-casein WS2 microspheres show higher content of water absorption and retention properties than only alginate-containing microspheres. The apatite formation in the simulated bodily fluid solution was facilitated more effectively by the alginate-casein-WS2 microspheres. Additionally, alginate-casein-WS2 microspheres have a compressive strength is 58.01 ± 4 MPa. Finally, in vitro cell interaction studies reveals that both the microspheres are biocompatible with the C3H10T1/2 cells, and alginate-casein-WS2-based microspheres promote cell growth more significantly. Alginate-casein-WS2 microspheres promote alkaline phosphatase activity, and mineralization process. Additionally, alginate-casein-WS2-based microspheres exponentially enhance the genes for ALP, BMP-2, OCN, and Collage type-1. The produced alginate-casein-WS2 microspheres could be a suitable synthetic graft for a bone transplant replacement.

Casein-Coated Molybdenum Disulfide Nanosheets Augment the Bioactivity of Alginate Microspheres for Orthopedic Applications

Defects and disorders of the bone due to disease, trauma, or abnormalities substantially affect a person's life quality. Research in bone tissue engineering is motivated to address these clinical needs. The present study demonstrates casein-mediated liquid exfoliation of molybdenum disulfide (MoS₂) and its coupling with alginate to create microspheres to engineer bone graft substitutes. Casein-exfoliated nano-MoS₂ was chemically characterized using different analytical techniques. The UV-visible spectrum of nano-MoS₂-2 displayed strong absorption peaks at 610 and 668 nm. In addition, the XPS spectra confirmed the presence of the molybdenum (Mo, 3d), sulfur (S, 2p), carbon (C, 1s), oxygen (O, 1s), and nitrogen (N, 1s) elements. The exfoliated MoS₂ nanosheets were biocompatible with the MG-63, MC3T3-E1, and C2C12 cells at 250 μg/mL concentration. Further, microspheres were created using alginate, and they were characterized physiochemically and biologically. Stereomicroscopic images showed that the microspheres were spherical with an average diameter of 1 ± 0.2 mm. The dispersion of MoS₂ in the alginate matrix was uniform. The alginate-MoS₂ microspheres promoted apatite formation in the SBF (simulated body fluid) solution. Moreover, the alginate-MoS₂ was biocompatible with MG-63 cells and promoted cell proliferation. Higher alkaline phosphatase activity and mineralization were observed on the alginate-MoS₂ with the MG-63 cells. Hence, the developed alginate-MoS₂ microsphere could be a potential candidate for a bone graft substitute.

Application Progress of Modified Chitosan and Its Composite Biomaterials for Bone Tissue Engineering

In recent years, bone tissue engineering (BTE), as a multidisciplinary field, has shown considerable promise in replacing traditional treatment modalities (i.e., autografts, allografts, and xenografts). Since bone is such a complex and dynamic structure, the construction of bone tissue composite materials has become an attractive strategy to guide bone growth and regeneration. Chitosan and its derivatives have been promising vehicles for BTE owing to their unique physical and chemical properties. With intrinsic physicochemical characteristics and closeness to the extracellular matrix of bones, chitosan-based composite scaffolds have been proved to be a promising candidate for providing successful bone regeneration and defect repair capacity. Advances in chitosan-based scaffolds for BTE have produced efficient and efficacious bio-properties via material structural design and different modifications. Efforts have been put into the modification of chitosan to overcome its limitations, including insolubility in water, faster depolymerization in the body, and blood incompatibility. Herein, we discuss the various modification methods of chitosan that expand its fields of application, which would pave the way for future applied research in biomedical innovation and regenerative medicine.

Osteon-mimetic 3D nanofibrous scaffold enhances stem cell proliferation and osteogenic differentiation for bone regeneration

The scaffold microstructure is important for bone tissue engineering. Failure to synergistically imitate the hierarchical microstructure of the components of bone, such as an osteon with concentric multilayers assembled by nanofibers, hinders the performance for guiding bone regeneration. Here, a 2D bilayer nanofibrous membrane (BLM) containing poly(lactide-co-glycolide) (PLGA)/polycaprolactone (PCL) composite membranes in similar compositions (PCL15 and PCL20), but possessing different degrees of shrinkage, was fabricated via sequential electrospinning. Upon incubation in phosphate buffered saline (PBS) (37 °C), the 2D BLM spontaneously deformed into a 3D shape induced by PCL crystallization within the PLGA matrix, and the PCL15 and PCL20 layer formed a concave and convex surface, respectively. The 3D structure contained curved multilayers with an average diameter of 776 ± 169 μm, and on the concave and convex surface the nanofiber diameters were 792 ± 225 and 881 ± 259 nm, respectively. The initial 2D structure facilitated the even distribution of seeded cells. Adipose-derived stem cells from rats (rADSCs) proliferated faster on a concave surface than on a convex surface. For the 3D BLM, the osteogenic differentiation of rADSCs was significantly higher than that on 2D surfaces, even without osteogenic supplements, which resulted from the stretched cell morphology on the curved sublayer leading to increased expression of lamin-A. After being implanted into cranial defects in Sprague Dawley (SD) rats, 3D BLM significantly accelerated bone formation. In summary, 3D BLM with an osteon-like structure provides a potential strategy to repair bone defects.

Recent advances in chitosan-based layer-by-layer biomaterials and their biomedical applications

In recent years, chitosan-based biomaterials have been continually and extensively researched by using layer-by-layer (LBL) assembly, due to their potentials in biomedicine. Various chitosan-based LBL materials have been newly developed and applied in different areas along with the development of technologies. This work reviews the recent advances of chitosan-based biomaterials produced by LBL assembly. Driving forces of LBL, for example electrostatic interactions, hydrogen bond as well as Schiff base linkage have been discussed. Various forms of chitosan-based LBL materials such as films/coatings, capsules and fibers have been reviewed. The applications of these biomaterials in the field of antimicrobial applications, drug delivery, wound dressings and tissue engineering have been comprehensively reviewed.

Chitosan grafted/cross-linked with biodegradable polymers: A review

Public perception of polymers has been drastically changed with the improved plastic management at the end of their life. However, it is widely recognised the need of developing biodegradable polymers, as an alternative to traditional petrochemical polymers. Chitosan (CH), a biodegradable biopolymer with excellent physiological and structural properties, together with its immunostimulatory and antibacterial activity, is a good candidate to replace other polymers, mainly in biomedical applications. However, CH has also several drawbacks, which can be solved by chemical modifications to improve some of its characteristics such as solubility, biological activity, and mechanical properties. Many chemical modifications have been studied in the last decade to improve the properties of CH. This review focussed on a critical analysis of the state of the art of chemical modifications by cross-linking and graft polymerization, between CH or CH derivatives and other biodegradable polymers (polysaccharides or proteins, obtained from microorganisms, synthetized from biomonomers, or from petrochemical products). Both techniques offer the option of including a wide variety of functional groups into the CH chain. Thus, enhanced and new properties can be obtained in accordance with the requirements for different applications, such as the release of drugs, the improvement of antimicrobial properties of fabrics, the removal of dyes, or as scaffolds to develop bone tissues.

Methods for the Assembly and Characterization of Polyelectrolyte Multilayers as Microenvironments to Modulate Human Mesenchymal Stromal Cell Response

Thin films are of interest in materials design because they allow for the modification of surface properties of materials while the bulk properties of the material are largely unaffected. In this work, we outline methods for the assembly of thin films using a technique known as layer-by-layer (LbL). Furthermore, their interactions with human mesenchymal stromal cells (hMSCs) are discussed. hMSCs are a subject of growing interest because of their potential to treat or cure diseases, given their immunosuppressive properties, multipotent differentiation capabilities, and tissue regeneration capabilities. Numerous improvements and modifications have been suggested for the harvesting, treatment, and culture of hMSCs prior to their administration in human subjects. Here, we discuss methods to assess the interactions of hMSCs with thin LbL-assembled films of heparin and collagen. Three different methods are discussed. The first details the preparation of heparin/collagen multilayers on different surfaces and the seeding of cells on these multilayers. The second method details the characterization of multilayers, including techniques to assess the thickness, roughness, and surface charge of the multilayers, as well as in situ deposition of multilayers. The third method details the analysis of cell interactions with the multilayers, including techniques to assess proliferation, viability, real-time monitoring of hMSC behavior, analysis of hMSC-adhesive proteins on the multilayers, immunomodulatory factor expression of hMSCs, and cytokine expression on heparin/collagen multilayers. We propose that the methods described in this work will assist in the design and characterization of LbL-assembled thin films and the analysis of hMSCs cultured on these thin films.

Layer-by-layer self-assembly polyelectrolytes loaded with cyclic adenosine monophosphate enhances the osteo/odontogenic differentiation of stem cells from apical papilla

Cyclic adenosine monophosphate (cAMP) is a second messenger involved in the dental regeneration. However, efficient long-lasting delivery of cAMP that is sufficient to mimic the in vivo microenvironment remains a major challenge. Here, cAMP was loaded in stem cells from apical papilla (SCAPs) using layer-by-layer self-assembly with gelatin and alginate polyelectrolytes (LBL-cAMP-SCAPs). LBL-cAMP-SCAPs expressed cAMP and increased the phosphorylation level of cAMP-response element-binding protein (CREB) which were evaluated by immunofluorescence and western blotting (WB). Enzyme-linked immunosorbent assay (ELISA) demonstrated that a sustained release of cAMP and vascular endothelial growth factor (VEGF) were present up to 14 days. Scanning electron microscopy (SEM) found LBL-coated SCAPs exhibited a spheroid-like morphology. CCK8 and live/dead staining showed that LBL treatment had no significant effect on cell proliferation and viability. LBL-cAMP-SCAPs enhanced mineralized nodule formation and up-regulated the mRNA levels of the osteogenesis-related genes, as well as related transcription factor-2 protein level which were revealed by Alizarin red staining, RT-PCR and WB, respectively. In conclusion, LBL self-assembly loaded with cAMP promoted the osteo/odontogenic differentiation of SCAPs, thereby providing a potential strategy for bioactive molecular delivery in dental regeneration.

Inhibition of CXCR4 inhibits the proliferation and osteogenic potential of fibroblasts from ankylosing spondylitis via the Wnt/β‑catenin pathway

Ankylosing spondylitis (AS) is an autoimmune condition characterized by chronic inflammation and abnormal ossification as the primary features of the disease. The aim of the present study was to investigate the role of C‑X‑C chemokine receptor type 4 (CXCR4) in ossification from patients with AS. CXCR4 expression was assessed by western blot analysis and immunohistochemistry analysis of tissues obtained from patients with AS and controls. Fibroblasts were isolated, cultured and incubated with AMD 3100 and stromal cell‑derived factor‑1 to inhibit and promote CXCR4 levels, respectively. CXCR4 was upregulated in hip synovial tissues from patients with AS compared with that observed in controls. AS fibroblasts exhibited increased proliferation and growth rates. Inhibition of CXCR4 increased the phosphorylation of β‑catenin and downregulated the expression of β‑catenin, v‑myc avian myelocytomatosis viral oncogene homolog, cyclin D1 and osteocalcin. Alizarin red staining demonstrated a decrease in biomineralization activity following the inhibition of CXCR4. These data support the hypothesis that inhibiting CXCR4 in patients with AS may suppress the ossification of fibroblasts.

Surface Modification of Dental Titanium Implant by Layer-by-Layer Electrostatic Self-Assembly

In vivo implants that are composed of titanium and titanium alloys as raw materials are widely used in the fields of biology and medicine. In the field of dental medicine, titanium is considered to be an ideal dental implant material. Good osseointegration and soft tissue closure are the foundation for the success of dental implants. Therefore, the enhancement of the osseointegration and antibacterial abilities of titanium and its alloys has been the focus of much research. With its many advantages, layer-by-layer (LbL) assembly is a self-assembly technique that is used to develop multilayer films based on complementary interactions between differently charged polyelectrolytes. The LbL approach provides new methods and applications for the surface modification of dental titanium implant. In this review, the application of the LbL technique to surface modification of titanium including promoting osteogenesis and osseointegration, promoting the formation and healing of soft tissues, improving the antibacterial properties of titanium implant, achieving local drug delivery and sustained release is summarized.

Generation of a co-culture cell micropattern model to simulate lung cancer bone metastasis for anti-cancer drug evaluation

A549/OB co-culture micropattern was fabricated through μ-eraser strategy to mimic lung cancer bone metastasis for DOX efficacy evaluation.