Multi-Stimuli-Responsive Janus Hollow Polydopamine Nanotubes

Abstract

A tubular-shaped Janus nanoparticle based on polydopamine that responds to near-infrared, magnetic, and pH stimuli is reported. The robust tubular polydopamine structure was obtained by optimizing the halloysite template-to-dopamine ratio during synthesis. The inner and outer surfaces of the tube were exposed at different steps of the template−sonication−-etching process, enabling the differential surface modification of these surfaces. Poly(ethylene glycol) (PEG) and poly(N-isopropylacrylamide) (PNIPAM) were grafted to the outer and inner surface of the nanotube, respectively. The PEG-coated surface limited aggregation of the nanoparticles at elevated temperatures. The PNIPAM-coated interior enhanced doxorubicin loading and endowed the nanoparticle with temperature-responsive behavior. The deposition of precipitated Fe 3 O 4 nanoparticles further modified the nanoparticles. The resulting magnetic Janus nanoparticles responded to pH, temperature, and magnetic fields. Temperature changes could be induced by near-infrared laser, and all three stimuli were found to influence release rates of adsorbed doxorubicin from the nanoparticles. The interaction of the stimuli on release kinetics was elucidated using a linear mixed model; reduced pH and NIR irradiation enhanced release while applying a static magnetic field retarded release. Furthermore, the mechanism was shifted toward Fickian behavior by applying a static magnetic field and low pH conditions. However, NIR irradiation only shifted the behavior toward Fickian behavior at low pH.

Interactions of Melanin with Electromagnetic Radiation: From Fundamentals to Applications

“…(b) Schematic illustrations of synthesis of PDA with different morphologies: (i) template method: PDA is first coated on a variety of templates, followed by stretching the resultant PDA composites, or removing the templates using different chemicals, resulting in ellipsoidal and hollow (Reproduced with permission from ref . Copyright 2019 American Chemical Society), porous (Reproduced with permission from ref , Copyright 2021 American Chemical Society), tubular (Reproduced with permission from refs , . Copyright 2016 American Chemical Society.…”

“…Copyright 2018 John Wiley and Sons), (ix, x) nanotubes ([ix] was reproduced with permission from ref . Copyright 2016 American Chemical Society; [x] was reproduced with permission from ref . Copyright 2022 American Chemical Society), (xi) nanofibers (Reproduced with permission from ref .…”

“…A large number of reviews have comprehensively discussed PDA, and metal–phenolic systems in terms of their syntheses and fundamentals. ,− Nevertheless, morphology of PDA has long been limited to spherical particles, and efforts have not been made until recently to obtain other morphologies (e.g., ellipsoidal). − ,,, These newly developed protocols and their updated formation mechanism have not been included in any reviews yet. In addition, since the starting precursors and properties of the metal–phenolic systems are analogous to plant melanin, these systems may be defined as “melanin-like” materials.…”

“…17,159 PDA is also coated on polystyrene (PS) particles, and the PDA-coated PS is embedded into PVA with subsequent stretching, which gives rise to ellipsoidal PDA@PS particles (Figure 5b, (i) and c, (ii)). 126 Further, coating PDA on PS or other templates (e.g., mesoporous silica [SiO 2 ], 16 curcumin, 21 DNA origami 19 ), followed by chemical removal of these templates (i.e., tetrahydrofuran [THF] for PS, 17 hydrofluoric acid [HF] for SiO 2 , 16 acetone for curcumin, 21 and HCl for DNA origami 19 ) (Figure 5b, (i)), or synthesizing PDA with some additives (e.g., P123, F127, folic acid [FA]) (Figure 5b, (ii,iii)), 20,23 results in nanostructures with more shapes, including hollow (Figure 5c, (iii)), 17 capsule-like (Figure 5c, (iv,v)), 18 porous (Figure 5c, (vi)), 16 cross pattern (Figure 5c, (vii)), 19 walnut-like (Figure 5c, (viii)), 20 tubular (Figure 5c, (ix,x)), 21,22,166 and fibrous (Figure 5c, (xi)). 23 PDA nanosheets were obtained by removing the large size of the synthesized PDA with a "liquid cascade centrifugation" strategy and maintaining the supernatant where the nanosheets accumulate (Figure 5c, (xii)).…”

“…These functions, together with the presence of functional groups (hydroxyl, carboxylic, or catechol groups) that possibly endow strong interactive forces (e.g., hydrogen bonding) between melanin and its combined materials, provide opportunities for creation of the next generation of advanced functional materials for diverse applications . The past two decades have seen an explosion of studies on the design of multifunctional materials based on polydopamine (PDA), a material that approximates eumelanin. − Efforts have also been extended, in the past five years, toward many more melanin analogues that includes PDA with morphologies beyond solid spherical ones, − synthetic allomelanin, − pheomelanin-like materials, , and polymeric materials prepared from tyrosine-derivatives. − These efforts aim to replicate melanin’s native functions by mimicking its intrinsic chemistries or morphologies. However, in some cases, we still lack an understanding of melanin’s interactions with its surroundings, which is needed for mimicry of its functions.…”