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Inspired by nature, we combine the easy decoration of polydopamine with the attractive biomimetic silification to develop a facile synthetic route toward raspberry-like nanocomposite particles, and further lead to the superhydrophobic and superoleophilic surfaces by mimicking the lotus leaf surface structures in the usage of these particles. In this approach, monodisperse polystyrene (PS) particles are used as the template particles, and then, follows with a subsequent polydopamine (PDA) coating step through the self-polymerization of dopamine in a weakly alkaline aqueous environment (pH = 8.5). The obtained core–shell PS/PDA particles are used as the active substrates for the biomimetic silification under the ambient conditions, allowing a well-controlled synthesis of raspberry-like PS/SiO 2 nanocomposite particles with a tunable surface roughness. Upon adjusting the concentration of silica precursor, the surface geometry and the coverage degree of silica nanoparticles of PS/PDA composite particles can be easily tailored. The whole procedure is carried out in a mild environment, no intricate instruments or toxic reagents are involved. In addition, these raspberry-like PS/SiO 2 nanocomposite particles self-assemble onto the glass slides driven by capillary force during drying, forming a hierarchical dual-sized rough structure, which is analogous to the surface morphology of lotus leaf in nature. Making full use of this hierarchical surface, superhydrophobic and superoleophilic surfaces can be successfully achieved via a rational surface modification of this lotus leaf-like surface structure. The superhydrophobic performances can be readily adjusted by varying the scale ratio of the micro/nano surface structures. [ABSTRACT FROM AUTHOR]

Mussel-inspired chemistry (polydopamine) offers great opportunities to develop inexpensive and efficient process for many types of materials with complex shapes and functions in a mild and friendly environment. This paper describes a facile, yet green approach to synthesize polydopamine/silver (PDA/Ag) nanocomposite particles with a combination use of polydopamine chemistry and electroless metallization of Ag. In this approach, monodisperse spherical polydopamine particles are first synthesized by the oxidation and self-polymerization of dopamine (monomer) in an alkaline water–ethanol solution at room temperature, which are served as the active templates for secondary reactions due to the abundant catechol and amine groups on the surface. Subsequently, the silver precursor-[Ag(NH 3 ) 2 ] + ions introduced are easily absorbed onto the surface of the PDA particles, and are immediately in situ reduced to metallic Ag nanoparticles with the help of these active catechol and amine groups. During the preparation, no additional reductants, toxic reagents and intricate instruments are needed. These as-synthesized PDA/Ag nanocomposite particles are ideal candidates for antibacterial application because they do not show significant cytotoxicity against HEK293T human embryonic kidney cells in the in vitro cytotoxicity assay, whereas demonstrate enhanced antibacterial abilities against Escherichia coli (Gram-negative bacteria) and Staphylococcus aureus (Gram-positive bacteria) in the antibacterial assays. Owing to their excellent cytocompatibilities and antibacterial activities, these PDA/Ag nanocomposite particles can be considered as the promising antibacterial materials for future biomedical applications. [ABSTRACT FROM AUTHOR]

Polydopamine/hydroxyapatite/nisin (PDA/HAP/Nisin) composites with good bioactivities and enhanced antibacterial activities are achieved and can serve as ideal antimicrobial biomaterials for biomedical application. Microbial contamination caused by bacterial adhesion and colonization onto the materials surfaces has long been a serious threat to human health. Thus, it is imperative to develop advanced antimicrobial materials for bio-applications. Here, a unique polydopamine/ hydroxyapatite/nisin (PDA/HAP/Nisin) composite with good bioactivities and enhanced antibacterial activities have been developed. The uniform PDA particles are first prepared via the dopamine self-polymerization in an alkaline water-ethanol mixed solvent. Due to the abundance surface catecholamine moieties, PDA particles can serve as the powerful templates for the in-situ mineralization of hydroxyapatite (HAP) in a simulated body fluid (SBF) solution, forming PDA/HAP composites. Transmission electron microscopy, scanning electron microscopy, transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction are used to investigate the morphology, surface composition, and crystalline structure of the PDA/HAP composites. These PDA/HAP composites are utilized as the reservoir for loading the antimicrobial peptide–nisin. Ultraviolet visible spectrophotometry analysis shows that PDA/HAP composites have exhibited a high loading capacity and a superior loading efficiency for nisin. The resulting PDA/HAP/Nisin composites are ideal antimicrobial biomaterials for bio-application because they exhibit not only a significant in vitro cytocompatibility to human embryonic kidney HEK293 T cells, but also the enhanced antibacterial activities against Staphylococcus aureus (Gram-positive bacteria). These advantageous properties of the PDA/HAP/Nisin composites allow them as the promising candidates for a broad range of bio-applications, e.g., drug delivery, implant engineering, and bio-scaffold. [ABSTRACT FROM AUTHOR]