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7. ZIF-8-decorated wood sponge derived from biomimetic mineralization of polydopamine

Author

Sun, Fei, Zhang, Mengjia, Zhu, Haixin, Huang, Yuewen, Song, Bin, Wang, Peijiang, Jiang, Shanshan, and Wang, Bin

Abstract

Zeolitic imidazolate framework-8 (ZIF-8) is extensively researched and used because of its exclusive structural and excellent physicochemical properties; however, significant challenges of alleviating the adverse effects of its particle form in many aspects are still faced by the scientific community. In this study, in situ growth of ZIF-8 within the pore channels and surfaces of green cellulose-based wood sponge was attempted through polydopamine-mediated incubation. The wood sponge was prepared by eliminating lignin and hemicellulose from natural balsa wood. Then, the sponge was impregnated with dopamine aqueous solution to yield polydopamine-covered wood sponge (PWS). ZIF-8 crystals were ultimately in situ grown in the substrate after sequential impregnation with zinc nitrate hexahydrate and 2-methylimidazole aqueous solutions at room temperature. Additionally, the effects of the deposition concentration of the dopamine aqueous solution and ZIF-8 incubation time were investigated. The obtained ZIF-8@PWS was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, Brunauer–Emmett–Teller analysis and thermogravimetric analysis. Finally, the toluene adsorption performance of porous ZIF-8@PWS in aqueous solution was also briefly evaluated, and it was demonstrated that the maximum adsorption capacity was 106.4 mg/g and the removal rate was as high as 94.2%. This work validates the envisioned universal protocol of preparing ZIF-8-decorated porous substrates through the integrated mediating role of polydopamine.

Published
2024
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13. Effect of working environment and procedural strategies on mechanical performance of bioresorbable vascular scaffolds

Author

Massachusetts Institute of Technology. Center for Biomedical Engineering, Massachusetts Institute of Technology. Institute for Medical Engineering & Science, Massachusetts Institute of Technology. Impact and Crashworthiness Laboratory, Massachusetts Institute of Technology. Department of Mechanical Engineering, Wang, Peijiang, Rikhtegar Nezami, Farhad, Gorji Bandpay, Maysam, Berti, Francesca, Petrini, Lorenza, Wierzbicki, Tomasz, Migliavacca, Francesco, Edelman, Elazer R, Massachusetts Institute of Technology. Center for Biomedical Engineering, Massachusetts Institute of Technology. Institute for Medical Engineering & Science, Massachusetts Institute of Technology. Impact and Crashworthiness Laboratory, Massachusetts Institute of Technology. Department of Mechanical Engineering, Wang, Peijiang, Rikhtegar Nezami, Farhad, Gorji Bandpay, Maysam, Berti, Francesca, Petrini, Lorenza, Wierzbicki, Tomasz, Migliavacca, Francesco, and Edelman, Elazer R

Abstract

Polymeric bioresorbable scaffolds (BRS), at their early stages of invention, were considered as a promising revolution in interventional cardiology. However, they failed dramatically compared to metal stents showing substantially higher incidence of device failure and clinical events, especially thrombosis. One problem is that use of paradigms inherited from metal stents ignores dependency of polymer material properties on working environment and manufacturing/deployment steps. Unlike metals, polymeric material characterization experiments cannot be considered identical under dry and submerged conditions at varying rates of operation. We demonstrated different material behaviors associated with variable testing environment and parameters. We, then, have employed extracted material models, which are verified by computational methods, to assess the performance of a full-scale BRS in different working condition and under varying procedural strategies. Our results confirm the accepted notion that slower rate of crimping and inflation can potentially reduce stress concentrations and thus reduce localized damages. However, we reveal that using a universal set of material properties derived from a benchtop experiment conducted regardless of working environment and procedural variability may lead to a significant error in estimation of stress-induced damages and overestimation of benefits procedural updates might offer. We conclude that, for polymeric devices, microstructural damages and localized loss of structural integrity should complement former macroscopic performance-assessment measures (fracture and recoil). Though, to precisely capture localized stress concentration and microstructural damages, context-related testing environment and clinically-relevant procedural scenarios should be devised in preliminary experiments of polymeric resorbable devices to enhance their efficacy and avoid unpredicted clinical events. Statement of Significance: Bioresorbable scaffolds (, National Institutes of Health (R01 GM 49039)

Published
2020

17. Bioresorbable scaffold: an integrated approach

Author

Wang, Peijiang

Subjects
Biomedical engineering
Abstract

Bioresorbable scaffolds (BRS) were thought to represent the next cardiovascular interventional revolution in relief of obstructive coronary atherosclerosis, yet they failed in comparison to metal stents. They were expected to provide mechanical support non-inferior to metal stents in short-term and gradually degrade to eliminate long-term complications associated with permanent implants. However, their clinical performances at all times were inferior to metal stents, including increased rate of thrombosis and myocardial infraction. These problems evaded detection, emerging only in clinical trials, leading one to wonder if BRS were appropriately characterized during the preclinical testing. We specifically questioned whether methods designed for metal stents could detect issues with BRS or hide potential areas of concerns. This work sought to determine how to define mechanical failure modes of BRS distinct from metal stents, and if such definition might have predicted clinical failure of the 1st generation BRS and if implemented now enable optimization of the design of next generation scaffolds. We developed a BRS-specific integrated approach involving benchtop mechanical testing, computational modelling, material characterization, and animal model validation evaluating de novo intact devices or those in which control defects were introduced. We performed mechanical characterizations with variable working environments and parameters. Micro-cracks and localized deformations were identified as a form of accelerated wear and challenge to structural integrity. We designed and built a high-throughput multimodal fatigue tester to generate deformation modes evident in arterial deformations in vivo, and test scaffold durability during acute and subacute timeframes. We reproduced fracture rates and locations seen in animal models, and revealed the relationship between loading modes, scaffold design, and fracture initiation and propagation. Finally, we utilized Raman spectroscopy to identify heterogeneities in material microstructures, which induced non-uniform degradation and severe localized deformations that could explain early structural failures and late clinical complications. Failure modes of BRS are distinct from those of bare metal stents and techniques designed to detect the one are not readily appropriate for the other. Characterization of device performance matched to device design might enable more appropriate device design.

Published
2018

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