Polymer-based nanocomposites such as polycaprolactone/graphene oxide (PCL/GO) have emerged as alternatives for bone tissue engineering (BTE) applications. The objective of this research was to investigate the impact of a gelatin (Gt) coating on the degradability and different properties of PCL nanofibrous scaffolds fabricated by an electrospinning technique with 1 and 2 wt% GO. Uniform PCL/GO fibers were obtained with a beadless structure and rough surface. PCL/GO scaffolds exhibited an increase in their crystallization temperature (Tc), attributed to GO, which acted as a nucleation agent. Young’s modulus increased by 32 and 63% for the incorporation of 1 and 2 wt% GO, respectively, in comparison with neat PCL. A homogeneous Gt coating was further applied to these fibers, with incorporations as high as 24.7 wt%. The introduction of the Gt coating improved the hydrophilicity and degradability of the scaffolds. Bioactivity analysis revealed that the hydroxyapatite crystals were deposited on the Gt-coated scaffolds, which made them different from their uncoated counterparts. Our results showed the synergic effect of Gt and GO in enhancing the multifunctionality of the PCL, in particular the degradability rate, bioactivity, and cell adhesion and proliferation of hGMSC cells, making it an interesting biomaterial for BTE.

Although the architectural design parameters of 3D-printed polymer-based scaffolds—porosity, height-to-diameter (H/D) ratio and pore size—are significant determinants of their mechanical integrity, their impact has not been explicitly discussed when reporting bulk mechanical properties. Controlled architectures were designed by systematically varying porosity (30–75%, H/D ratio (0.5–2.0) and pore size (0.25–1.0 mm) and fabricated using fused filament fabrication technique. The influence of the three parameters on compressive mechanical properties—apparent elastic modulus E_app, bulk yield stress σ_y and yield strain ε_y—were investigated through a multiple linear regression analysis. H/D ratio and porosity exhibited strong influence on the mechanical behavior, resulting in variations in mean E_app of 60% and 95%, respectively. σ_y was comparatively less sensitive to H/D ratio over the range investigated in this study, with 15% variation in mean values. In contrast, porosity resulted in almost 100% variation in mean σ_y values. Pore size was not a significant factor for mechanical behavior, although it is a critical factor in the biological behavior of the scaffolds. Quantifying the influence of porosity, H/D ratio and pore size on bench-top tested bulk mechanical properties can help optimize the development of bone scaffolds from a biomechanical perspective.

Direct ink writing (DIW) is an attractive, extrusion-based, additive manufacturing method for fabricating scaffold structures with controlled porosity using custom composite inks. Polycaprolactone–bioactive glass (PCL-BG) inks have gained attention for bone applications, but optimizing the formulation and fabrication of PCL-BG-based inks for improved printability and desired mechano-biological properties remains a challenge. This study employs a two-step design to systematically evaluate the effect of three factors in terms of PCL-BG composite printability and mechano-biological properties: ink preparation (acetone or dichloromethane (DCM) as the solvent, and mechanical compounding), the extrusion temperature (90 °C, 110 °C, and 130 °C), and the BG content (0%, 10%, and 20% BG). Pure PCL was used as the control. Rheological, calorimetric, and thermo-gravimetric analyses were conducted before printing. Cylindrical scaffolds and solid wells were printed to evaluate the printability, mechanical properties, and cytocompatibility. The scaffold porosity and pore size were carefully examined. Mechanical tests demonstrated that composite formulations with added BG and higher printing temperatures increased the elastic modulus and yield strength. However, PCL-DCM-BG combinations exhibited increased brittleness with higher BG content. Despite concerns about the toxic solvent DCM, the cytocompatibility was comparable to pure PCL for all ink preparation methods. The results suggest that the interaction between the ink preparation solvent, the BG content, and the printing temperature is critical for material design and fabrication planning in bone tissue engineering applications, providing insights into optimizing PCL-BG composite ink formulations for 3D printing in bone tissue engineering.

Aminochrome, an endogenous neurotoxin, has been suggested that it is implicated in the loss of dopaminergic neurons that contain neuromelanin in the nigrostriatal system in Parkinson's disease. While aminochrome-induced oxidative stress, as well as its inhibitory effects on microtubule polymerization in neuronal models, are well documented, its impact on autophagosome–lysosome fusion and protein aggregation remains unexplored. The aim of this research was to evaluate the effects of aminochrome on the fusion between autophagosomes and lysosomes, and the accumulation of protein aggregated using SH-SY5Y cells differentiated into dopaminergic neurons. Our findings reveal that aminochrome like vinblastine, delays the fusion of autophagosomes with lysosomes, as evidenced by decreased colocalization of LC3β-LAMP1. This effect was also observed after the addition of autophagy inductors such as rapamycin and trehalose. Moreover, rapamycin and trehalose mitigate aminochrome-induced cell death, whereas vinblastine exacerbates it. Bafilomycin A1, despite reducing LC3β-LAMP1 colocalization, offers protection against aminochrome-induced cytotoxicity. These disruptions in autophagosome-lysosome fusion are associated with accumulation of perinuclear vimentin and ubiquitin aggregates together with increased colocalization between vimentin and ubiquitin. Interestingly, the presence of ubiquitin aggregates at the nuclear level were also observed. It is postulated that the effect of aminochrome on the microtubule network, particularly inhibition of the autophagosome-lysosome fusion and the accumulation of protein aggregates, could be one of the critical events that lead to cell death. Our findings underscore the therapeutic potential of targeting microtubule stabilization and autophagy/UPS induction in Parkinson's disease, an energy-dependent process, highlighting the need for further research into nuclear proteotoxicity mechanisms.

Aminochrome, an endogenous neurotoxin, has been implicated in the loss of neuromelanin-containing dopaminergic neurons in the nigrostriatal system in Parkinson’s disease. Although aminochrome-induced oxidative stress and its inhibitory effects on microtubule polymerization are well documented, its impact on protein aggregation remains poorly understood. The aim of this research was to evaluate the effects of aminochrome on protein aggregate accumulation in SH-SY5Y cells differentiated into dopaminergic neurons. While the role of aminochrome in autophagy has been described, its direct effect on autophagosome–lysosome fusion has not been studied. Our findings reveal that aminochrome, like vinblastine, delays autophagosome–lysosome fusion and induces cell death. This inhibitory effect was also observed in the presence of autophagy inducers, which partially attenuated aminochrome-induced cell death. Under these conditions of disruptions in autophagosome–lysosome fusion, a marked accumulation of perinuclear vimentin and ubiquitin aggregates was observed. Aminochrome also increased colocalization between vimentin and ubiquitin. Interestingly, ubiquitin aggregates were also detected within the nucleus. These findings suggest that aminochrome-induced disruption of the microtubule network, particularly its impairment of autophagosome–lysosome fusion and promotion of protein aggregation, may represent a critical mechanism leading to cell death. In addition, inhibition of autophagosome–lysosome fusion may contribute to the accumulation of perinuclear and nuclear protein aggregates, which may be associated with either toxic or non-toxic pathways. Our findings underscore the therapeutic potential of targeting both microtubule stabilization and proteostasis pathways, including autophagy and the ubiquitin–proteasome system (UPS), in Parkinson’s disease, highlighting the need for further research into nuclear proteotoxicity mechanisms.