Two-photon microscopy for microrobotics: Visualization of micro-agents below fixed tissue.

Optical microscopy is frequently used to visualize microrobotic agents (i.e., micro-agents) and physical surroundings with a relatively high spatio-temporal resolution. However, the limited penetration depth of optical microscopy techniques used in microrobotics (in the order of 100 µm) reduces the capability of visualizing micro-agents below biological tissue. Two-photon microscopy is a technique that exploits the principle of two-photon absorption, permitting live tissue imaging with sub-micron resolution and optical penetration depths (over 500 µm). The two-photon absorption principle has been widely applied to fabricate sub-millimeter scale components via direct laser writing (DLW). Yet, its use as an imaging tool for microrobotics remains unexplored in the state-of-the-art. This study introduces and reports on two-photon microscopy as an alternative technique for visualizing micro-agents below biological tissue. In order to validate two-photon image acquisition for microrobotics, two-type micro-agents are fabricated and employed: (1) electrospun fibers stained with an exogenous fluorophore and (2) bio-inspired structure printed with autofluorescent resin via DLW. The experiments are devised and conducted to obtain three-dimensional reconstructions of both micro-agents, perform a qualitative study of laser-tissue interaction, and visualize micro-agents along with tissue using second-harmonic generation. We experimentally demonstrate two-photon microscopy of micro-agents below formalin-fixed tissue with a maximum penetration depth of 800 µm and continuous imaging of magnetic electrospun fibers with one frame per second acquisition rate (in a field of view of 135 × 135 µm2). Our results show that two-photon microscopy can be an alternative imaging technique for microrobotics by enabling visualization of micro-agents under in vitro and ex ovo conditions. Furthermore, bridging the gap between two-photon microscopy and the microrobotics field has the potential to facilitate in vivo visualization of micro-agents.

Hyperbaric oxygen for idiopathic sudden hearing loss: is the routine application helpful?

CONCLUSION: We recommend the routine application of hyperbaric oxygen (HBO) in conjunction with intravenous steroid (IVS) for all patients with idiopathic sudden sensorineural hearing loss (ISSNHL). For best results, this therapy must be started within 14 days. OBJECTIVE: To investigate the necessity of routine application of HBO therapy for ISSNHL. METHODS: This was a retrospective cohort study. A total of 300 patients (300 diseased ears) were divided into 3 groups according to the therapy received: IVS (group A), HBO (group B), or IVS + HBO (group C). Patients in each treatment group were subdivided into subgroups according to the time of therapy initiation. The outcomes of their hearing recovery were classified into three recovery grades: good, fair, and poor. RESULTS: The proportion of patients responding to therapy and those with complete recovery was the highest in the combined treatment group, 84% and 58%, respectively, regardless of the initial hearing levels. In all the groups, mean gains of cases in whom therapy was started in the first 2 weeks were significantly higher (p < 0.05) and hypercholesterolemia (>240 mg/dl) caused significantly worse responses (p < 0.05).