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The development of bone repair scaffolds has long been a research hotspot in tissue engineering. Owing to its unique capability for personalized customization of scaffold geometry and microstructure, 3D printing technology has been extensively adopted for fabricating bone repair scaffolds. Poly-L-lactic acid (PLLA), endowed with favorable biodegradability, excellent biocompatibility, and reliable in vivo safety, is widely used as a matrix material for 3D printed bone repair scaffolds. PLLA is a bioinert polymer characterized by inferior cell adhesion and osteogenic differentiation capabilities. To mitigate this bioinertness limitation, the present study employed N-methylpyrrolidone (NMP) etching to modify the surface of 3D-printed PLLA bone repair scaffolds. Following NMP etching for 1–24 h, the originally smooth scaffold surface evolved into a hierarchical, petal-like gradient microstructure, accompanied by a marked increase in surface roughness. Correspondingly, the hydrophilicity of the treated scaffolds was also enhanced. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses further confirmed that the crystallinity of PLLA in the scaffolds was significantly enhanced. Concomitantly, the modified scaffolds exhibited a marked improvement in adsorption capacity for green fluorescent protein (GFP), while the adhesion and proliferation of MC3T3-E1 on their surface were also significantly promoted. In vivo animal experiments demonstrated that the NMP-etched scaffolds could accelerate the process of bone defect repair. Collectively, surface modification of 3D-printed PLLA bone scaffolds via NMP etching enables precise modulation of their physicochemical properties, thereby effectively mitigating the inherent bioinertness limitation of PLLA scaffolds. Graphical Abstract

The development of an effective scaffold for bone defect repair is an urgent clinical need. However, it is challenging to design a scaffold with efficient osteoinduction and antimicrobial activity for regeneration of bone defect. In this study, we successfully prepared a hydroxyapatite (HA) porous scaffold with a surface-specific binding of peptides during osteoinduction and antimicrobial activity using a three-dimensional (3D) printing technology. The HA binding domain (HABD) was introduced to the C-terminal of bone morphogenetic protein 2 mimetic peptide (BMP2-MP) and antimicrobial peptide of PSI10. The binding capability results showed that BMP2-MP and PSI10-containing HABD were firmly bound to the surface of HA scaffolds. After BMP2-MP and PSI10 were bound to the scaffold surface, no negative effect was observed on cell proliferation and adhesion. The gene expression and protein translation levels of type I collagen (COL-I), osteocalcin (OCN) and Runx2 have been significantly improved in the BMP2-MP/HABP group. The level of alkaline phosphatase significantly increased in the BMP2-MP/HABP group. The inhibition zone test against Staphylococcus aureus and Escherichia coli BL21 prove that the PSI10/HABP@HA scaffold has strong antibacterial ability than another group. These findings suggest that 3D-printed HA scaffolds with efficient osteoinduction and antimicrobial activity represent a promising biomaterial for bone defect reconstruction.

Observational studies have suggested an association between inflammatory markers and low back pain (LBP), but the causal relationship between these factors remains uncertain. We conducted a bidirectional two-sample Mendelian randomization analysis (MR) study to investigate whether there is a causal relationship between inflammatory markers and low back pain. We obtained genetic data for CRP, along with its upstream inflammatory markers IL-6, IL-8, and IL-10, as well as low back pain from publicly available genome-wide association studies (GWAS). We applied several MR methods, including inverse variance weighting, weighted median, MR-Egger, Wald Ratio, and MR-PRESSO, to test for causal relationships. Sensitivity analyses were also conducted to assess the robustness of the results. Our analyses utilizing the Inverse Variance Weighted (IVW) method, the MR-Egger method, and the weighted median method indicated that IL-6 may be associated with an increased risk of LBP (Effect Size: -0.009, 95% Confidence Interval: -0.013-0.006, p = 9.16e-08); however, in the reverse direction, there was no significant causal effect of LBP on inflammatory markers. Our study used a Mendelian randomization approach and found that elevated IL-6 levels may reduce the risk of LBP.

Zhongxing Liu,1,2,* Mengzhe Tian,3,* Lincheng Duan21Dujiangyan Traditional Chinese Medicine Hospital, Chengdu, Sichuan, People’s Republic of China; 2Chengdu University of Traditional Chinese Medicine, Chengdu, Sichuan, People’s Republic of China; 3Chengdu Sport University, Chengdu, Sichuan, People’s Republic of China*These authors contributed equally to this workCorrespondence: Lincheng Duan, Chengdu University of Traditional Chinese Medicine, Chengdu, Sichuan, People’s Republic of China, Email [email protected]View the original paper by Ms Chai and colleaguesA Response to Letter has been published for this article.

[This corrects the article DOI: 10.3389/fimmu.2023.1174656.].

Electroconductive hydrogels (EHs) are promising composite biomaterials of hydrogels and conductive electroactive polymers, incorporating bionic physicochemical properties of hydrogels and conductivity, electrochemistry, and electrical stimulation (ES) responsiveness of conductive electroactive polymers. The biomedical domain has increasingly seen EHs’ application to imitating the biological and electrical properties of human tissues, acclaimed as one of the most effective biomaterials. Bone’s complex bioelectrochemical properties and the corresponding stem cell differentiation affected by electrical signal elevate EHs’ application value in repairing and treating bone, cartilage, and skeletal muscle. Noteworthily, the latest orthopedic biological applications require broader information of EHs. Except for presenting the classification and synthesis of EHs, this review recapitulates the advance of EHs application to orthopedics in the past five years and discusses the pertinent development tendency and challenge, aiming to provide a reference for EHs application direction and prospect in orthopedic therapy.