Central Taiwan University of Science and Technology

StoS is a hybrid histidine kinase that, to date, has been investigated only in Xanthomonas oryzae pathovar oryzae. In this study, we elucidated the function and transcriptional regulation of the stoS gene in X. campestris pathovar campestris (Xcc). An stoS deletion mutant and its complemented strain were constructed to assess phenotypic characteristics. Inactivation of StoS markedly decreased tolerance to heat, sodium dodecyl sulfate, and hydrogen peroxide, impaired membrane integrity, and reduced stationary-phase survival, whereas complementation restored these phenotypes. Transcriptional mapping identified a guanine residue 22 nucleotides upstream of the start codon as the transcription start site. Promoter activity assays further revealed that stoS expression is regulated by nutrient availability and environmental stress. Together, these results demonstrate that stoS plays a crucial role in maintaining membrane stability and stress resilience in Xcc. By providing the first functional characterization of stoS in Xcc, this study extends its investigation beyond X. oryzae pathovar oryzae and advances current understanding of stress-adaptive regulation in Xanthomonas.

This study presents the development of a lead-based molecular probe integrated with an extended-gate field-effect transistor (EGFET) for the highly sensitive detection of lead ions (Pb2+). The molecular probe was carefully selected and engineered to exhibit a strong binding affinity for Pb2+ while maintaining both thermodynamic stability and structural robustness. To enhance sensing performance, we employed a pulsed temperature profile strategy that accelerates molecular interactions and overcome energy barriers, followed by a stabilization step to preserve the integrity of the formed complexes. Through this approach, the sensor achieved an ultralow detection limit of 1 pM, highlighting the crucial role of molecular probe structural stability and thermodynamic properties in improving overall sensing efficiency. DNA linkers functionalized with reactive groups and fluorescent labels were employed to enable real-time monitoring of surface modification and facilitate efficient molecular immobilization, thereby enhancing the sensor's versatility. Moreover, constructing a monolayer sensing interface allowed direct regulation of the electric double layer (EDL), resulting in rapid signal responses. Selectivity tests confirmed the sensor's preferential interaction with Pb2+ ions. Overall, this study developed an innovative sensing platform that achieves ultralow detection limits and high selectivity for Pb2+. The platform is highly versatile and can be extended to EGFET-based sensing of a wide range of molecules.

This study presents a novel surface modification strategy for the low-modulus beta-type Ti-13Nb-7Sn-4Mo alloy to enhance its bioactivity for biomedical implants. A hierarchical micro-/submicro-/nano-structured surface was developed, incorporating a Ca(1-x)SrxTiO3 layer and metallic Ag nanoparticles. Elemental analysis showed surface concentrations of 2.61 f 0.39 at.% Ca, 1.14 f 0.23 at.% Sr, and 0.21 f 0.14 at.% Ag. X-ray photoelectron spectroscopy confirmed the presence of TiO2, Nb2O5, SnO2, MoO2, MoO3, Mo2O5, CaTiO3, SrTiO3, and metallic Ag. Water contact angles of 23.7 degrees for NT-Ca and 29.1 degrees for NT-Ca-Sr-Ag indicated moderate surface hydrophilicity. In simulated body fluid, all samples initiated apatite formation within one day. However, the NT-Ca-Sr-Ag surface exhibited faster and denser apatite growth after 14 days compared to the NT sample. The average weight gains of the NT, NT-Ca, and NT-Ca-Sr-Ag samples were measured as 2.87 f 0.3 mg/cm2, 2.93 f 0.45 mg/cm2, and 3.10 f 0.4 mg/cm2, respectively. These results demonstrate that the hierarchical Ca(1-x)SrxTiO3/nanotube surface combined with Sr and Ag incorporation enhances the surface's apatite-forming ability. The presence of Sr may enhance bioactivity, while Ag provides potential antibacterial activity. Although antibacterial performance was not directly tested in this study, the combined incorporation of Ca, Sr, and Ag on a hierarchical surface structure represents a novel design strategy with clear clinical relevance for Ti-based implants.

Titanium (Ti) and its alloys are widely used as hard tissue implants due to their excellent mechanical strength, corrosion resistance, and biocompatibility. However, their bioinert nature limits osseointegration, requiring surface modification to enhance biological responses. In this study, a hierarchical micro/submicro/nano-textured bioactive surface was constructed on a metastable beta-type Ti-13Nb-7Sn-4Mo alloy using anodization, microwave annealing, and hydrothermal treatment with a sustainable Ca source. The microwave annealing process produced crystalline TiO2 nanotube arrays with either anatase or mixed anatase/rutile phases, allowing investigation of phase-dependent CaTiO3 formation while preserving nanotube morphology. Subsequent hydrothermal treatment employed oyster shell-derived biogenic Ca to synthesize CaTiO3 on the nanotube surfaces. The selective nucleation and growth of CaTiO3 on anatase versus rutile phases generated distinct surface architectures, with partial decoration by micron- and submicron-sized CaTiO3 crystallites at 180 degrees C and complete coverage at 190 degrees C. The anatase-rich surfaces (M500H180) exhibited more uniform CaTiO3 coverage, better preserved nanotube structure, and enhanced surface hydrophilicity, which collectively promoted surface-induced mineralization behavior, as evidenced by apatite formation after 14 days in simulated body fluid. This study demonstrates a novel, eco-friendly strategy for fabricating phase-controlled CaTiO3 coatings on Ti-based alloys using biogenic Ca, highlighting the synergistic effects of TiO2 crystalline phase, hierarchical surface morphology, and sustainable Ca sources. The developed surfaces offer both environmental and functional advantages, providing a promising strategy for phase-controlled ceramic surface functionalization on Ti-based alloys.