WashU affiliated authors: Hamed Gholami Derami (Dept. of Mechanical Engineering and Materials Science)
Abstract: Polydopamine (PDA), a synthetic and organic material, has emerged as a promising material platform for various applications in energy, environmental, and biomedical fields. PDA, formed by self-polymerization of dopamine, is rich in catechol and amine groups, which facilitate covalent conjugation and/or other non-covalent interactions with organic and inorganic materials. It is highly biocompatible, biodegradable, has broadband light absorption spectrum and excellent light-to-heat conversion efficiency. Also, it is easy to synthesize and functionalize. The combination of excellent characteristics of polydopamine-based nanomaterials, make them a promising adsorbent agent for environmental wastewater treatment and photothermal agent for biomedical applications.
In the first half of thesis, we utilize the surface chemical functionality of polydopamine nanoparticles and their affinity to heavy metal ions and organic dyes to realize multifunctional filtration membranes that remove heavy metal ions and organic dyes from water through adsorption and catalytic degradation. Polydopamine exhibits high adsorption capacity toward heavy metal ions and organic dyes. Adsorption-based membrane technologies can be ideal for continuous flow water purification and have been extensively employed at industrial scale for water reclamation. By introducing polydopamine nanoparticles during bacteria-mediated cellulose growth, we fabricated a composite foam and membrane to study the adsorption behavior of the nanocomposites in different environmentally relevant pH and concentrations. The PDA/BNC membrane was used to investigate the removal efficiency of toxic heavy metals ions such as Pb (II) and Cd (II) and organic pollutants such as rhodamine 6G and methylene blue. Furthermore, to improve the range of pH in which the composite membrane is effective for dye removal, we fabricated another novel polydopamine/nanocellulose membrane, which is decorated with palladium (Pd) nanoparticles to remove organic dyes from contaminated water through catalytic dye degradation.
In the second part of thesis, we develop polydopamine-based nanomaterials and experimental setups to be used in biomedical applications such as drug delivery and photothermal stimulation of cells. Using mesoporous silica-coated PDA nanoparticles as drug carrier and tetradecanol (TD) as gate keeper, we demonstrated that we could enhance the immune system response toward Melanoma cancer in mouse model through combination of photothermal and immunotherapy. Polydopamine core works as a photothermal agent to cause localized release of gardiquimod and tumor cell death upon NIR laser irradiation, hence, release of tumor associated antigens. Antigen presenting cells (APCs) including the dendritic cells and macrophages uptake these antigens and be activated around tumor site in response to these signals. Furthermore, these activated APCs, present the antigen to CD8+ cytotoxic T cells to actuate anti-tumor immune response. We have shown that this treatment is effective in reducing the tumor size and eliminating it in majority of cases. Also, the treatment created a memory effect in immune system toward melanoma cancer when second cancer event happened in mice that were treated before.
Finally, we investigated the possibility of controlling the excitable cells’ activity through nanoheating. This was made possible by using polydopamine nanoparticles to localize the heat on cell membrane. We demonstrated that by using polydopamine nanoparticle and polydopamine/collagen 3D foam, and by applying NIR laser light, we can reversibly modulate the activity of in vitro cultured neurons and cardiomyocytes. A reduction in firing rate of neurons and an increase in beating rate of cardiomyocytes with different degree of inhibition and excitation was observed. Effect of different parameters on the quality of modulation was investigated.