Abstract
Fast imaging of molecular changes under high-resolution and label-free conditions are essential for understanding in-vivo processes, however, current techniques are not able to monitor such changes in real time. Polarization sensitive second harmonic generation (PSHG) imaging is a minimally invasive optical microscopy technique capable of quantifying molecular conformational changes occurring below the diffraction limit. Up to now, such information is generally retrieved by exciting the sample with different linear polarizations. This procedure requires the sample to remain static during measurements (from a few second to minutes), preventing the use of PSHG microscopy from studying moving samples or molecular dynamics in living organisms. Here we demonstrate an imaging method that is one order of magnitude faster than conventional PSHG. Based on circular polarization excitation and instantaneous polarimetry analysis of the second harmonic signal generated in the tissue, the method is able to instantaneously obtain molecular information within a pixel dwell time. As a consequence, a single scan is only required to retrieve all the information. This allowed us to perform PSHG imaging in moving C. elegans, monitoring myosin's dynamics during the muscular contraction and relaxation. Since the method provides images of the molecular state, an unprecedented global understanding of the muscles dynamics is possible by correlating changes in different regions of the sample.
Highlights
Second harmonic generation (SHG) is a promising technique for totally non-invasive highresolution optical imaging [1]
The results above shows that SS-Polarization-based SHG (PSHG) has similar capabilities that standard PSHG in retrieving molecular information in static samples, such as starch, collagen, myosin and microtubules
To standard PSHG, the theoretical model does not take into account changes caused by the tissue birefringence or scattering on both, the excitation and the SHG polarization
Summary
Second harmonic generation (SHG) is a promising technique for totally non-invasive highresolution optical imaging [1]. This non-linear non-resonant contrast mechanism is offering intrinsic advantages over linear optical imaging, such as optical sectioning, reduced photodamage and deeper tissue penetration depth. The contrast, generated from specific SHG active molecules is endogenous and as a consequence, no additional modification of the sample is required [2]. Polarization-based SHG (PSHG) imaging takes advantage of the molecular structure [3,4,5,6,7] and the differentiated response with respect the excitation polarization to reveal geometrical details at the molecular level in a quantitative way [8]. PSHG microscopy is a promising tool in disease diagnosis [9] and biological research for studies in cornea [10, 11], muscle [12], osteogenesis imperfecta [13] ischemia [14] and aging [15]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
