Bioresorbable Microdroplet Lasers as Injectable Systems for Transient Thermal Sensing and Modulation

Abstract

Minimally invasive methods for temperature sensing and thermal modulation in living tissues have extensive applications in biological research and clinical care. As alternatives to bioelectronic devices for this purpose, functional nanomaterials that self-assemble into optically active microstructures offer important features in remote sensing, injectability, and compact size. This paper introduces a transient, or bioresorbable, system based on injectable slurries of well-defined microparticles that serve as photopumped lasers with temperature-sensitive emission wavelengths (>4−300 nm °C−1 ). The resulting platforms can act as tissue-embedded thermal sensors and, simultaneously, as distributed vehicles for thermal modulation. Each particle consists of a spherical resonator formed by self-organized cholesteric liquid crystal molecules doped with fluorophores as gain media, encapsulated in thin shells of soft hydrogels that offer adjustable rates of bioresorption through chemical modification. Detailed studies highlight fundamental aspects of these systems including particle sensitivity, lasing threshold, and size. Additional experiments explore functionality as photothermal agents with active temperature feedback (ΔT = 1 °C) and potential routes in remote evaluation of thermal transport properties. Cytotoxicity evaluations support their biocompatibility, and ex vivo demonstrations in Casper fish illustrate their ability to measure temperature within biological tissues with resolution of 0.01 °C. This collective set of results demonstrates a range of multifunctional capabilities in thermal sensing and modulation.

Droplet Lasers for Smart Photonic Labels

“…Specifically, a droplet with smaller size contains a smaller volume of excitable gain medium and thus, the resonance efficiency of the radial cavity is lowered. 41 Representative emission spectra corresponding to RhB droplets with different sizes are reported in Figure 3C. The emission is shifted toward smaller wavelength with decreasing the cavity size, spanning in a broad spectral range determined by the RhB fluorescence emission band.…”

“…The energy thresholds corresponding to the onset of lasing are determined from the intersection of the two linear regimes and fall in the range 8–130 μJ for all the droplets analyzed with variations that depend on the droplet size. Specifically, a droplet with smaller size contains a smaller volume of excitable gain medium and thus, the resonance efficiency of the radial cavity is lowered …”

“…Specifically, a droplet with smaller size contains a smaller volume of excitable gain medium and thus, the resonance efficiency of the radial cavity is lowered. 41 …”

Wireless Power Transfer and Telemetry for Implantable Bioelectronics

“…In this study, RF‐based WPT and telemetry strategies used for various implantable devices, such as sensors, [ 64 ] stimulators, [ 65 ] and drug injectors, [ 66 ] are reviewed ( Figure a). First, RF‐based WPT strategies (e.g., near‐field power transfer and radiative power transfer) that devise appropriate materials [ 67–69 ] and/or component designs to specific applications are discussed (Figure 1b).…”

Self-Assembled Biophotonic Lasing Network Driven by Amyloid Fibrils in Microcavities

“…Unlike conventional networks, “biophotonic networks” represent a distinctive fashion for investigating the light–matter interaction with biological networks, providing a wealth of interesting physical phenomena. ,,,, Various approaches have therefore been studied to increase the interaction of light with biological structures. − Optical cavities, which possess the ability to enhance light–matter interaction by confining photons in small volumes, have played an important role in modern optics, lasing, and sensing applications. − Integrating biophotonic network with optical cavity can significantly amplify tiny heterogeneity in biological structures. As shown in Figure a, when a biophotonic network is confined in a microcavity formed by two highly reflective mirrors, the photons emitting from networks couple with the external Fabry–Perot (FP) cavities, creating a series of “mirror images” of the biological network with enhanced features.…”