Visible‐Light‐Triggered Drug Release from TiO₂ Nanotube Arrays: A Controllable Antibacterial Platform

Abstract

Abstract:In this work, we use a double-layered stack of TiO 2 nanotubes (TiNTs) to construct a visible-light triggered drug delivery system. Key for visible-light drug release is a hydrophobic cap on the nanotubes containing Au nanoparticles (AuNPs). The AuNPs allow for a photocatalytic scission of the hydrophobic chain under visible light. To demonstrate the principle, we loaded antibiotic (ampicillin sodium (AMP)) in the lower part of the TiO 2 nanotube stack, triggered visible light induced release, and carried out antibacterial studies. The release from the platform becomes most controllable if the drug is silane-grafted in hydrophilic bottom layer for drug storage. Thus visible-light photocatalysis can also determine the release kinetics of the active drug from the nanotube wall.2 Controllable drug delivery has attracted wide interest in biomedicine and other fields of science in order to achieve a targeted use of an active substance at the right time and the right place.Particularly drug release mechanisms with triggers that respond to surrounding factors, such as pH, [1] temperature, [2] illumination and ionic strength [3] are of a high practical significance. Many nanomaterials are, or can be designed to be particularly sensitive to environmental factors and therefore a steeply increasing number of studies is being carried out on the development of "smart" nanomaterial-based drug carriers. Systems have been developed with great biocompatibility and the feasibility of targeted drug delivery with a much higher control over the pharmacokinetics (which can decrease systemic toxicity). [4,5] For example, Dai and his coworkers prepared pH-sensitive polyethylene glycol functionalized graphene oxide for the delivery of aromatic drugs, [6a, 6b] or hierarchical hollow CaCO 3 nanoparticles have been reported for a localizing drug release reacting on a pH change. [6c] Another example is the work of Zhang et al. that reported a free-radical precipitation polymerization method to synthesize a temperature responding drug carrier. [7] As drug carrier a wide range of nanoparticles, [8] microgel, [9] nanotubes [10,11] and polymeric micelles [12, 2b] have been explored. Especially, drug carriers based on nanotubes have various beneficial features due to their intrinsic high surface-to-volume ratio, well defined geometry and stable structure. [13] In the past decade TiO 2 nanotube arrays (TiNTs) grown by a self-organizing electrochemical anodization process have attracted tremendous scientific interest due to the combination of geometric features with an inherent photocatalytic activity. TiNTs have shown great potential in optics, energy storage, bioelectronics as well as for medical devices. [14] Biocompatible scaffolds for hosting functional guest molecules can be fabricated, taking advantage of the large number of hydroxyl groups present on the tube walls. These provide the possibility of incorporating desired functional groups, to load drugs or graft capping molecules and thus establish advanced storage and relea...

Titanium Dioxide Nanoparticles: Prospects and Applications in Medicine

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Visible light to switch-on desorption from goethite

“…The visible light triggered release of adsorbed ions/molecules from the surface of nanoparticles could open a wide range of novel applications including drug delivery, sedimentation, desalination, change in pH, optical devices based on ionic dyes and sensing. 1,2 Light can be further used to induce the mechanical response of materials 3,4 or fluorescence switching which is applicable in sensors and fluorescent logic devices. [5][6][7] Access to this untapped abundant source of energy offers a safe, easy and readily accessible means to switch-on or switchoff different phenomena.…”

Photoactivated drug delivery and bioimaging

“…These ROS demonstrates effective cytotoxicty and would be able to destroy tumor cell structures, and thus achieve the targeted cell death in vitro and in vivo. 52 55 In this rational design, the AuNPs could also act as photocatalyst, which can generate active radical species, e.g., O˙2 or OH˙, under visible light illumination to cleave the linkage group between AuNPs and TiO 2 nanotube. So the payload molecules inside the TiO 2 nanotube could diffuse into the surroundings and exhibited the promising drug activity.…”