Zhiyi Du1,Mingsheng Li1,Guo Chen1,Maijie Xiang1,Nan Zheng1,Chen Yang1,Jixin Cheng1
Boston University1
Zhiyi Du1,Mingsheng Li1,Guo Chen1,Maijie Xiang1,Nan Zheng1,Chen Yang1,Jixin Cheng1
Boston University1
Photoacoustic has been shown as an emerging method for imaging and cellular modulation in biomedical applications. Up to this date generation of photoacoustic signals in photoacoustic agents and materials relies on absorption based on the electronic transitions in visible range such as gold nanoparticles or NIR range such as carbon based materials. However, operation in these wavelengthes will also interfere with other imaging modality using the same range. For example, successfully photoacoustic modulation has been achieved using carbon materials that broadly absorb while quality of Ca imaging when recording neuron responses upon modulation can be affected. Here, we show for the first time the intrinsic vibrational transition of C-H bond upon absorption of MIR can lead to efficient photoacoustic conversion. Specifically, owing to the high concentration of C-H bond in it, PDMS film was shown to generate 3 MPa photoacoustic pressure at 10 μm away from acoustic source under 2960 cm<sup>-1</sup> laser illumination, corresponding to 190 N/J PA conversion efficiency. Such a high PA conversion is comparable to the widely developed CNT/PDMS PA device. Successful photoacoustic neurostimulation of GCaMP6f labeled cortical neurons cultured on PDMS film has been demonstrated and validated using Ca imaging. Taking the advantage of high transparency of PDMS film in visible and NIR range, especially at the GCaMP6f fluorescence excitation and emission wavelengths (i.e., 497 and 512 nm), Ca imaging can be performed in both epi and trans modes with substantially improved imaging quality. By focusing the illumination area, neuromodulation with high spatial resolution of 5-10 microns can be achieved to enable single neuron and subcellular stimulation. Given the fact that C-H bond is commonly existed in most of the organic materials and has the absorption far away from visible range, we herein provide a universal method to fabricate transparent photoacoustic film highly compatible with fluorescence imaging.