Optical manipulation of plasmonic nanoparticles provides opportunities for fundamental and technical innovation in nanophotonics. Optical heating arising from the photon-to-phonon conversion is considered as an intrinsic loss in metal nanoparticles, which limits their applications. We show here that this drawback can be turned into an advantage, by developing an extremely low-power optical tweezing technique, termed opto-thermoelectric nanotweezers (OTENT). Through optically heating a thermoplasmonic substrate, alight-directed thermoelectric field can be generated due to spatial separation of dissolved ions within the heating laser spot, which allows us to manipulate metal nanoparticles of a wide range of materials, sizes and shapes with single-particle resolution. In combination with dark-field optical imaging, nanoparticles can be selectively trapped and their spectroscopic response can be resolved in-situ. With its simple optics, versatile low-power operation, applicability to diverse nanoparticles, and tuneable working wavelength, OTENT will become a powerful tool in colloid science and nanotechnology.

Our study highlights the overactivated neddylation pathway in lung cancer development and as a promising therapeutic target.

Reversible assembly of plasmonic nanoparticles can be used to modulate their structural, electrical, and optical properties. Common and versatile tools in nanoparticle manipulation and assembly are optical tweezers, but these require tightly focused and high-power (10-100 mW/μm) laser beams with precise optical alignment, which significantly hinders their applications. Here we present light-directed reversible assembly of plasmonic nanoparticles with a power intensity below 0.1 mW/μm. Our experiments and simulations reveal that such a low-power assembly is enabled by thermophoretic migration of nanoparticles due to the plasmon-enhanced photothermal effect and the associated enhanced local electric field over a plasmonic substrate. With software-controlled laser beams, we demonstrate parallel and dynamic manipulation of multiple nanoparticle assemblies. Interestingly, the assemblies formed over plasmonic substrates can be subsequently transported to nonplasmonic substrates. As an example application, we selected surface-enhanced Raman scattering spectroscopy, with tunable sensitivity. The advantages provided by plasmonic assembly of nanoparticles are the following: (1) low-power, reversible nanoparticle assembly, (2) applicability to nanoparticles with arbitrary morphology, and (3) use of simple optics. Our plasmon-enhanced thermophoretic technique will facilitate further development and application of dynamic nanoparticle assemblies, including biomolecular analyses in their native environment and smart drug delivery.

Diabetic wound healing is one of the major challenges in the biomedical fields. The conventional single drug treatments have unsatisfactory efficacy, and the drug delivery effectiveness is restricted by the penetration depth. Herein, we develop a magnesium organic framework-based microneedle patch (denoted as MN-MOF-GO-Ag) that can realize transdermal delivery and combination therapy for diabetic wound healing. Multifunctional magnesium organic frameworks (Mg-MOFs) are mixed with poly­(γ-glutamic acid) (γ-PGA) hydrogel and loaded into the tips of MN-MOF-GO-Ag, which slowly releases Mg2+ and gallic acid in the deep layer of the dermis. The released Mg2+ induces cell migration and endothelial tubulogenesis, while gallic acid, a reactive oxygen species-scavenger, promotes antioxidation. Besides, the backing layer of MN-MOF-GO-Ag is made of γ-PGA hydrogel and graphene oxide-silver nanocomposites (GO-Ag) which further enables excellent antibacterial effects for accelerating wound healing. The therapeutic effects of MN-MOF-GO-Ag on wound healing are demonstrated with the full-thickness cutaneous wounds of a diabetic mouse model. The significant improvement of wound healing is achieved for mice treated with MN-MOF-GO-Ag.