Browsing by Author "Wang, Wenbo"

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    Effects of Chemical and Structural Heterogeneity on the Tribocorrosion Resistance of Metals in Aqueous Solutions
    Wang, Wenbo (Virginia Tech, 2022-06-27)
    The corrosion-wear resistance tradeoff in conventional metals imposes a great challenge to their reliable long-term performance under extreme conditions where surface stress and corrosive environment coexist (i.e., tribocorrosion). In this work, strategies to introduce chemical and structural heterogeneity with controlled length-scale at nanometers were proposed and studied in three metallic systems (i.e., Zr-based, Al-based and Mg-based), in order to enhance their tribocorrosion resistance. In the first study, ZrCuNiAl thin film metallic glasses (TFMG) with either homogeneous or heterogeneous local composition were deposited by magnetron sputtering through controlling processing conditions (i.e., argon (Ar) pressure). It was found that the mechanical properties, wear, corrosion and tribocorrosion resistance of ZrCuNiAl TFMG were significantly affected by nanoscale chemical heterogeneity. As a result, nanoscale chemical heterogeneity promoted ductility but reduced hardness, which in turn weakened wear resistance. While, in the 0.6 M NaCl solution, the resistance to pitting corrosion and tribocorrosion was improved because the presence of nanoscale chemical heterogeneity facilitates to generate more protective passive layer with lower defect density and faster repassivated capability, compared to their homogenous counterparts. In the second study, nanoscale chemical and structural heterogeneity were introduced in Al by forming Al/X nanostructured metallic multilayers (NMMs), where X=Mg, Cu, and Ti. Compared to the respective monolithic films, the alternating nanolayer configuration not only increased strength due to the presence of abundant interfaces but also reduced surface activity and pitting susceptibility. The electrochemical performance was significantly affected by the interaction, i.e., galvanic effect, between Al layer and underlayer constituents, which in turn led to different tribocorrosion behaviors, Specifically, transmission electron microscopy revealed that the materials loss in Al/Mg and Al/Cu NMMs primarily resulted from corrosion, while Al/Ti was dominated by severe plastic deformation during tribocorrosion as a result of sustained surface passivity. Lastly, in the bulk biodegradable Mg alloys system, the surface was treated by femtosecond laser shock peening (fs-LSP) technique with ultra-low pulse energy to introduce structural heterogeneity. Treatment conditions (e.g., power density, direct ablation and confined ablation) significantly affected the ultimate peening effect and further surface performance. In this work, the optimized peening effect was obtained at 28 GW/cm2 laser power density in the confined ablation with the assistance of the adsorption layer and confining medium. Combined with transmission electron microscopy and finite element analysis, the improvement of surface performance was attributed to high dislocation density near the surface, rather than compressive residual stress. The existence of structural heterogeneity not only reduced corrosion kinetics but simultaneously improved the self-repassivation in the blood bank buffered saline solution at body temperature.
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    Noncovalently particle-anchored cytokines with prolonged tumor retention safely elicit potent antitumor immunity
    Niu, Liqian; Jang, Eungyo; Chin, Ai Lin; Huo, Ziyu; Wang, Wenbo; Cai, Wenjun; Rong, Tong (American Association for the Advancement of Science, 2024-04-19)
    Preclinical studies have shown that immunostimulatory cytokines elicit antitumor immune responses but their clinical use is limited by severe immune-related adverse events upon systemic administration. Here, we report a facile and versatile strategy for noncovalently anchoring potent Fc-fused cytokine molecules to the surface of size-discrete particles decorated with Fc-binding peptide for local administration. Following intratumoral injection, particle-anchored Fc cytokines exhibit size-dependent intratumoral retention. The 1-micrometer particle prolongs intratumoral retention of Fc cytokine for over a week and has minimal systemic exposure, thereby eliciting antitumor immunity while eliminating systemic toxicity caused by circulating cytokines. In addition, the combination of these particle-anchored cytokines with immune checkpoint blockade antibodies safely promotes tumor regression in various syngeneic tumor models and genetically engineered murine tumor models and elicits systemic antitumor immunity against tumor rechallenge. Our formulation strategy renders a safe and tumor-agnostic approach that uncouples cytokines’ immunostimulatory properties from their systemic toxicities for potential clinical application.