Physical stimulations and their osteogenesis-inducing mechanisms

Physical stimulations such as magnetic, electric and mechanical stimulation could enhance cell activity and promote bone formation in bone repair process via activating signal pathways, modulating ion channels, regulating bonerelated gene expressions, etc. In this paper, bioeffects of physical stimulations on cell activity, tissue growth and bone healing were systematically summarized, which especially focused on their osteogenesis-inducing mechanisms. Detailedly, magnetic stimulation could produce Hall effect which improved the permeability of cell membrane and promoted the migration of ions, especially accelerating the extracellular calcium ions to pass through cell membrane. Electric stimulation could induce inverse piezoelectric effect which generated electric signals, accordingly up-regulating intracellular calcium levels and growth factor synthesis. And mechanical stimulation could produce mechanical signals which were converted into corresponding biochemical signals, thus activating various signaling pathways on cell membrane and inducing a series of gene expressions. Besides, bioeffects of physical stimulations combined with bone scaffolds which fabricated using 3D printing technology on bone cells were discussed. The equipments of physical stimulation system were described. The opportunities and challenges of physical stimulations were also presented from the perspective of bone repair.

3D-printed scaffolds with bioactive elements-induced photothermal effect for bone tumor therapy

For treatment of bone tumor and regeneration of bone defects, the biomaterials should possess the ability to kill tumor cells and regenerate bone defect simultaneously. To date, there are a few biomaterials possessing such dual functions, the disadvantages, however, such as long-term toxicity and degradation, restrict their application. Although bioactive elements have been incorporated into biomaterials to improve their osteogenic activity, there is no report about elements-induced functional scaffolds for photothermal tumor therapy. Herein, the elements (Cu, Fe, Mn, Co)-doped bioactive glass-ceramic (BGC) scaffolds with photothermal effect and osteogenic differentiation ability were prepared via 3D-printing method. Moreover, the photothermal anti-tumor effect and osteogenic activity of these scaffolds were systematically investigated. The prepared elements-doped scaffolds possessed excellent photothermal performance, which displayed a trend, 5Cu-BGC > 5Fe-BGC > 5Mn-BGC > 5Co-BGC, in this study. The final temperature of elements-doped scaffolds can be well controlled by altering the doping element categories, contents and laser power density. Additionally, the hyperthermia induced by 5Cu-BGC, 5Fe-BGC and 5Mn-BGC effectively killed tumor cells in vitro and inhibited tumor growth in vivo. More importantly, 5Fe-BGC and 5Mn-BGC scaffolds could promote rabbit bone mesenchymal stem cells (rBMSCs) adhesion, and the ionic products released from elements-doped scaffolds significantly stimulated the osteogenic differentiation of bone-forming cells. These results suggested that 5Fe-BGC and 5Mn-BGC scaffolds possessed promising potential for photothermal treatment of bone tumor and at the same time for stimulating bone regeneration, representing a smart strategy for the treatment of bone tumors by combining dual functional bioactive ions with tissue engineering scaffolds.

STATEMENT OF SIGNIFICANCE

The major innovation of this study is that we fabricated the elements (Cu, Fe, Mn, Co)-doped bioactive scaffolds via 3D printing technique and found that they possess distinct photothermal performance and osteogenic differentiation ability. To the best of our knowledge, there is no report about elements-doped scaffolds for photothermal therapy of bone tumor. This is an important research advance by combining the photothermal effect and osteogenic differentiation activity of bioactive elements in the scaffold system for potential bone tumor therapy and bone reconstruction. We optimized the elements-doped scaffolds and found the photothermal effect of elements-doped scaffolds (5Cu-BGC, 5Fe-BGC, 5Mn-BGC) could effectively kill tumor cells in vivo. The photothermal performance of elements-doped scaffolds follows a trend: 5Cu-BGC > 5Fe-BGC > 5Mn-BGC > 5Co-BGC > BGC. Compared to traditional nano-sized photothermal agents, bioactive elements-induced functional scaffolds have better biosecurity and bioactivity. Furthermore, 5Fe-BGC and 5Mn-BGC scaffolds displayed excellent bone-forming activity by stimulating the osteogenic differentiation of bone-forming cells. The major significance of the study is that the elements-doped bioactive glass-ceramics (5Fe-BGC, 5Mn-BGC) have great potential to be used as bifunctional scaffolds for photothermal tumor therapy and bone regeneration, representing a smart strategy for the treatment of bone tumors by combining dual functional bioactive ions with tissue engineering scaffolds.

Fluorinated graphene as an anticancer nanocarrier: an experimental and DFT study

Both experimental and theoretical research was conducted to explore the performance of fluorinated graphene as a novel anticancer nanocarrier, and we also reported its first application in cancer chemo-photothermal therapy.

Long-term G1 cell cycle arrest in cervical cancer cells induced by co-immobilized TNF-α plus IFN-γ polymeric drugs

A realistic control of cell cycle arrest is an attractive goal for the development of new effective anti-cancer drugs. Any clinical application of an effective anti-cancer drug necessarily relies on the understanding of cellular interaction mechanisms. In the present study, we prepared a co-immobilized TNF-α plus IFN-γ biomaterial, which showed a significant inhibition effect on cervical cancer cell growth, as demonstrated by a series of structural and cellular characterizations. We found that co-immobilized TNF-α plus IFN-α induced a long-term G₁ phase cell cycle arrest in HeLa, SiHa, and CaSki cells, respectively. More surprisingly, the expression level of the p27 protein decreased, even when p27 mRNA was highly expressed. In addition, gene-chip results and microarray analysis showed that p57 may be downstream from p27, which acts as a direct regulator of the long-term G₁ cell cycle arrest in these cells, leaving no escape for cervical cancer cells. Finally, we also investigated the anti-tumor mechanism of co-immobilized TNF-α plus IFN-γin vivo, using a nude mice animal model. To sum up, our findings suggested that the co-immobilized TNF-α plus IFN-γ can induce a long-term cell cycle arrest in cancer, thus serving as a very efficient tool for treating cervical cancer.

3D-printed bioceramic scaffolds with antibacterial and osteogenic activity

Bacterial infection poses a significant risk with the wide application of bone graft materials. Designing bone grafts with good antibacterial performance and excellent bone-forming activity is of particular significance for bone tissue engineering. In our study, a 3D printing method was used to prepare β-tricalcium phosphate (β-TCP) bioceramic scaffolds. Silver (Ag) nanoparticles were uniformly dispersed on graphene oxide (GO) to form a homogeneous nanocomposite (named Ag@GO) with different Ag-to-graphene oxide mass ratios, with this being synthesized via the liquid chemical reduction approach. Ag@GO nanocomposites were successfully modified on the β-TCP scaffolds by a simple soaking method to achieve bifunctional biomaterials with antibacterial and osteogenic activity. The prepared scaffolds possessed a connected network with triangle pore morphology and the surfaces of the β-TCP scaffolds were uniformly modified by the Ag@GO nanocomposite layers. The Ag content in the scaffolds was controlled by changing the coating times and concentration of the Ag@GO nanocomposites. The antibacterial activity of the scaffolds was assessed with Gram-negative bacteria (Escherichia coli, E. coli). The results demonstrated that the scaffolds with Ag@GO nanocomposites presented excellent antibacterial activity. In addition, the scaffolds coated with Ag@GO nanocomposites conspicuously accelerated the osteogenic differentiation of rabbit bone marrow stromal cells by improving their alkaline phosphatase activity and bone-related gene expression (osteopontin, runt-related transcription factor 2, osteocalcin and bone sialoprotein). This study demonstrates that bifunctional scaffolds with a combination of antibacterial and osteogenic activity can be achieved for the reconstruction of large-bone defects while preventing or treating infections.

Targeting ligand-functionalized photothermal scaffolds for cancer cell capture and in situ ablation

Targeting ligands with different grafting densities were introduced into photothermal scaffolds for cancer cell specific capture and ablation.

Preparation of dexamethasone-loaded calcium phosphate nanoparticles for the osteogenic differentiation of human mesenchymal stem cells

Dexamethasone (DEX)-loaded biphasic calcium phosphate nanoparticles (BCP-NPs) are prepared by incorporation of DEX during or after the formation of BCP-NPs. The DEX-loaded BCP-NPs release DEX in a sustained manner and enhance the osteogenic differentiation of hMSCs.

Composite scaffolds of gelatin and gold nanoparticles with tunable size and shape for photothermal cancer therapy

Photothermal therapy (PTT) has been extensively investigated as a promising strategy for cancer therapy. For successful application of this technique, various nanomaterials have been explored as photothermal conversion agents. Gold nanoparticles (AuNPs), especially Au nanorods and Au nanostars, have received much attention for photothermal therapy because of their facile preparation and high photothermal conversion efficiency. Due to the limited accumulation and easy diffusion of free nanoparticles, incorporation of nanoparticles into scaffolds for direct implantation has been demonstrated as an attractive way for cancer therapy applications. In this study, composite porous scaffolds of gelatin and AuNPs were prepared by introducing Au nanorods and Au nanostars with average sizes of around 35.0, 65.0 and 115.0 nm in gelatin scaffolds. The composite scaffolds were used for the localized PTT application of cancer cells. Gel/AuNP composite scaffolds supported cell adhesion and showed good biocompatibility. Temperature in the composite scaffolds increased quickly upon NIR laser irradiation. Photothermal efficiency and cancer cell killing efficiency were dependent on the shape, size and amount of AuNPs in the composite scaffolds. The composite scaffolds prepared with 65.0 nm Au nanorods showed the highest photothermal efficiency and cell killing efficiency. The results indicated the importance of the shape and size modulation of AuNPs for photothermal therapy applications.

Comprehensive Review on the Use of Graphene-Based Substrates for Regenerative Medicine and Biomedical Devices

Recent research suggests that graphene holds great potential in the biomedical field because of its extraordinary properties. Whereas initial attempts focused on the use of suspended graphene for drug delivery and bioimaging, more recent work has demonstrated its advantages for preparing substrates for tissue engineering and biomedical devices and products. Cells are known to interact with and respond to nanoparticles differently when presented in the form of a substrate than in the form of a suspension. In tissue engineering, a stable and supportive substrate or scaffold is needed to provide mechanical support, chemical stimuli, and biological signals to cells. This review compiles recent advances of the impact of both graphene and graphene-derived particles to prepare supporting substrates for tissue regeneration and devices as well as the associated cell response to multifunctional graphene substrates. We discuss the interaction of cells with pristine graphene, graphene oxide, functionalized graphene, and hybrid graphene particles in the form of coatings and composites. Such materials show excellent biological outcomes in vitro, in particular, for orthopedic and neural tissue engineering applications. Preliminary evaluation of these graphene-based materials in vivo reinforces their promise for tissue regeneration and implants. Although the reported findings of studies on graphene-based substrates are promising, several questions and concerns associated with their in vivo use persist. Possible strategies to examine these issues are presented.

Preparation of gelatin/Fe3O4 composite scaffolds for enhanced and repeatable cancer cell ablation

Various nanomaterials have been extensively investigated for photothermal ablation of cancer cells because of their high photothermal conversion efficiency. However, the poor targeting specificity and low repeated heating efficiency of nanomaterials restrict their applications in the clinic. In this work, porous gelatin/iron oxide (Gel/Fe₃O₄) composite scaffolds were prepared by a facile ice particulate templating method for efficient and repeatable cancer cell ablation. Gel/Fe₃O₄ composite scaffolds showed controlled porous structure consisting of large pores and interconnecting small pores. The strong absorption in the near-infrared (NIR) region enabled the Gel/Fe₃O₄ composite scaffolds to elevate local temperature quickly under NIR laser irradiation. The composite scaffolds allowed cell adhesion and proliferation showing good biocompatibility. Cancer cells entrapped in the scaffolds could be efficiently killed during laser irradiation. Moreover, the therapeutic efficacy of Gel/Fe₃O₄ composite scaffolds could be enhanced by repeated laser irradiation treatment, which is important for clinical application because of the resistant and recurrent nature of cancer. The results indicated that the porous Gel/Fe₃O₄ composite scaffolds had good biocompatibility and excellent cancer cell ablation efficacy, which may provide an attractive way to use porous scaffolds for cancer therapy application.