Gold nanorods can be used as photothermal converters, permitting near-infrared (NIR) light to be transmitted deep into tissues without causing damage. We prepared hybrid nanorods with a core-shell structure, i.e., a single gold nanorod encapsulated in a poly (N-isopropylacrylamide) nanogel. Hybrid nanorods demonstrated remote, reversible, pulsatile phase transition and in vivo action after irradiation using a NIR laser.

No abstract

In this study, we prepared gold nanorod (NR)-embedded N-isopropylacrylamide (NIPAM) hydrogels and studied their volume phase transition behavior induced by near-infrared (near-IR) laser irradiation utilizing the photothermal conversion characteristics of the NRs. When poly(ethylene glycol)-modified NRs were used for the preparation of composite gels, the NRs showed marked dispersion stability in the gel. Near-IR laser irradiation of the gel (cylindrical shape, diameter = 140 microm) under the following conditions, NR concentrations in the gel > or =100 microM and laser irradiation power > or =490 mW, resulted in shrinkage of the gel in the following manner: (1) waist formation around the irradiation spot and (2) growth of the waist along the axial directions of the gel. The gel shrinking induced by near-IR irradiation occurred much more rapidly than that afforded by a temperature jump, because the former was not accompanied by the skin layer formation, which disturbs the rapid shrinking of the gels. When a composite gel containing the model drug (rhodamine-labeled dextran) was irradiated with a near-IR laser, the rapid release of the drug was observed. Taking advantage of the high spatial resolution of the irradiation point, we further achieved the irradiation-point-specific release of the drug from one such gel.

No abstract