Seeing, Targeting and Delivering with Upconverting Nanoparticles.

Efficient control over drug release is critical to increasing drug efficacy and avoiding side effects. An ideal drug delivery system would deliver drugs in the right amount, at the right location and at the right time noninvasively. This can be achieved using light-triggered delivery: light is noninvasive, spatially precise and safe if appropriate wavelengths are chosen. However, the use of light-controlled delivery systems has been limited to areas that are not too deep inside the body because ultraviolet (UV) or visible (Vis) light, the typical wavelengths used for photoreactions, have limited penetration and are toxic to biological tissues. The advent of upconverting nanoparticles (UCNPs) has made it possible to overcome this crucial challenge. UCNPs can convert near-infrared (NIR) radiation, which can penetrate deeper inside the body, to shorter wavelength NIR, Vis and UV radiation. UCNPs have been used as bright, in situ sources of light for on-demand drug release and bioimaging applications. These remote-controlled, NIR-triggered drug delivery systems are especially attractive in applications where a drug is required at a specific location and time such as in anesthetics, postwound healing, cardiothoracic surgery and cancer treatment. In this Perspective, we discuss recent progress and challenges as well as propose potential solutions and future directions, especially with regard to their translation to the clinic.

Raman Spectroscopy for Inverted Papilloma: A Proof-of-Concept Study.

Inverted papillomas are tumors of the sinonasal tract with a propensity to recur. Raman spectroscopy can potentially identify inverted papillomas from other tissue based on biochemical signatures. A pilot study comparing Raman spectroscopy to histopathology for 3 types of sinonasal tissue was performed. Spectral data of biopsies from patients with normal sinonasal mucosa, chronic rhinosinusitis, and inverted papillomas are compared to histopathology using principal component analysis and linear discriminant analysis after data preprocessing. A total of 18 normal, 15 chronic rhinosinusitis, and 18 inverted papilloma specimens were evaluated. The model distinguished normal sinonasal mucosa, chronic rhinosinusitis, and inverted papilloma tissue with an overall accuracy of 90.2% (95% confidence interval, 0.86-0.94). In conclusion, Raman spectroscopy can distinguish inverted papilloma, normal sinonasal mucosa, and chronically rhinosinusitis tissue with acceptable accuracy.

Nano graphene oxide-wrapped gold nanostars as ultrasensitive and stable SERS nanoprobes.

We report a facile method to synthesize highly branched gold nanostars wrapped with nano graphene oxide (nGO) sheets with or without the addition of Raman dyes, as nanoprobes with high SERS activity. Both cysteamine and nGO are added to gold nanostars; the positively charged amino groups help self-assembly of nGO flakes around the nanostars. This increases the Raman signal of nGO by 5.3 folds compared to samples in which nGO is in contact with the nanostars but does not wrap them. We also prepare dye-based SERS nanoprobes by sandwiching a typical Raman reporter such as Rhodamine B (RhB), Crystal Violet (CV) and Rhodamine 6G (R6G) between the nanostars and the nGO coating. The Raman signals of RhB are 5.2 times larger when sandwiched between nGO and nanostars than if the molecules are just adsorbed on the nanostar surface, and similar enhancements are observed for the other dyes. In addition to improving SERS efficiency, the wrapping greatly improves the stability of the dye-based nanoprobes, showing a reproducible Raman signal of RhB for over a week in simulated body fluids at 37 °C. High SERS signal, facile fabrication method and excellent stability make these nanoprobes highly promising for SERS-based biosensing and bioimaging applications.

Controlled biohybrid nanoprobes with silver nanoparticle clusters for Raman imaging.

A new class of biohybrid nanoprobes has been developed for surface-enhanced Raman scattering-based bioimaging. Silver nanoparticle clusters were encapsulated in polymeric nanoparticles using electrohydrodynamic jetting, followed by stabilization and bioconjugation. Controlled SERS intensity with high sensitivity, chemical stability, and biocompatibility makes the SERS biohybrid nanoprobes useful for bioimaging.