Optical trapping of optical nanoparticles:Fundamentals and applications

Optical nanoparticles are nowadays one of the key elements of photonics.They do not only allow optical imaging of a plethora of systems(from cells to microelectronics),but,in many cases,they also behave as highly sensitive remote sensors.In recent years,it has been demonstrated the success of optical tweezers in isolating and manipulating individual optical nanoparticles.This has opened the door to high resolution single particle scanning and sensing.In this quickly growing field,it is now necessary to sum up what has been achieved so far to identify the appropriate system and experimental set-up required for each application.In this review article we summarize the most relevant results in the field of optical trapping of individual optical nanoparticles.After systematic bibliographic research,we identify the main families of optical nanoparticles in which optical trapping has been demonstrated.For each case,the main advances and applications have been described.Finally,we also include our critical opinion about the future of the field,identifying the challenges that we are facing.

Infrared fluorescence imaging of infarcted hearts with A@S nanodots

Ag2S nano dots have already bee n dem onstrated as promisi ng n ear-i nfrared (NIR-II, 1.0-1.45 pm) emitting nan oprobes with low toxicity, high penetration and high resolution for in vivo imaging of, for example, tumors and vasculature. In this work, we have systematically investigated the pote ntial applicati on of function alized Ag2S nano dots for accurate imaging of damaged myocardium tissues after a myocardial in farction in duced by either partial or global ischemia. Ag2S nano dots surface-function alized with the an giote nsin II peptide (ATI I) have show n over 10-fold enhanced binding efficiency to damaged tissues than non-specifically (PEG) functionalized Ag2S nanodots due to their interaction with the upregulated angiotensin II receptor type I (AT1R). It is demonstrated how the NIR-II images generated by ATII-functionalized Ag2S nanodots contain valuable information about the location and extension of damaged tissue in the myocardium allowing for a proper identification of the occluded artery as well as an in direct evaluati on of the damage level. The pote ntial applicati on of Ag2S nano dots in the n ear future for in vivo imaging of myocardial infarction was also corroborated by performing proof of concept whole body imaging experiments.

Less is more:dimensionality reduction as a general strategy for more precise luminescence thermometry

Thermal resolution(also referred to as temperature uncertainty)establishes the minimum discernible temperature change sensed by luminescent thermometers and is a key figure of merit to rank them.Much has been done to minimize its value via probe optimization and correction of readout artifacts,but little effort was put into a better exploitation of calibration datasets.In this context,this work aims at providing a new perspective on the definition of luminescence-based thermometric parameters using dimensionality reduction techniques that emerged in the last years.The application of linear(Principal Component Analysis)and non-linear(t-distributed Stochastic Neighbor Embedding)transformations to the calibration datasets obtained from rare-earth nanoparticles and semiconductor nanocrystals resulted in an improvement in thermal resolution compared to the more classical intensity-based and ratiometric approaches.This,in turn,enabled precise monitoring of temperature changes smaller than 0.1℃.The methods here presented allow choosing superior thermometric parameters compared to the more classical ones,pushing the performance of luminescent thermometers close to the experimentally achievable limits.

New opportunities for light-based tumor treatment with an“iron fist”

The efficacy of photodynamic treatments of tumors can be significantly improved by using a new generation of nanoparticles that take advantage of the unique properties of the tumor microenvironment.