Thyroid nodule (TN), a discrete palpable swelling of the thyroid gland, is prevalent among 8% of the adult population. The important concern with these nodules is the differentiation between benign and malignant ones. Since conventional diagnostic techniques (e.g., ultrasound) are not accurate in diagnosis, clinical surgeons adopt to excision biopsy, a golden standard, which requires surgery and removal of the gland. We propose to apply Photoacoustic Spectral Response (PASR), a non-invasive and elasticity based diagnostic technique, onto TN for malignancy diagnosis. In this study, time domain photoacoustic signals were acquired through custom built experimental setup inside the surgical theatre and spectral information were obtained through signal processing. PA spectra could distinguish Follicular Variant of Papillary Thyroid Carcinoma (a thyroid cancer) from the other tissues with a high accuracy which an important challenge in conventional diagnostic techniques. Further, other tissue variants were also successfully differentiated through signal decomposition in a quantitative manner.
The feasibility of continuous wave laser-based photoacoustic (CWPA) response technique in detecting the morphological changes in cells during the biological studies, through the features extracted from CWPA signal (i.e., amplitude) is demonstrated here. Various hematological disorders (e.g., sickle cell anemia, thalesemia) produce distinct changes at the cellular level morphologically. In order to explore the photoacoustic response technique to detect these morphological changes, we have applied CWPA technique onto the blood samples. Results of our preliminary study show a distinct change in the signal amplitude of photoacoustic (PA) signal due to a change in the concentration of blood, which signifies the sensitivity of the technique towards red blood cell (RBC) count (related to hematological disease like anemia). Further hypotonic and hypertonic solutions were induced in blood to produce morphological changes in RBCs (i.e., swollen and shrink, respectively) as compared to the normal RBCs. Experiments were performed using continuous wave laser-based photoacoustic response technique to verify the morphological changes in these RBCs. A distinct change in the PA signal amplitude was found for the distinct nature of RBCs (swollen, shrink, and normal). Thus, this can serve as a diagnostic signature for different biological studies based on morphological changes at cellular level. The experiments were also performed using conventional pulsed laser photoacoustic response technique which uses nano-second pulsed laser and the results obtained from both PA techniques were validated to produce identical changes. This demonstrates the utility of continuous wave laser-based photoacoustic technique for different biological studies related to morphological cellular disorders.
In recent years, gold nanoparticles have emerged as promising agents for plasmonic sensing, photoacoustic imaging, photothermal therapy, and other biomedical applications. In this work, green synthesis of plant‐mediated gold nanoparticles (AuNPs) using an aqueous leaf extract of Pimenta dioica was carried out and the synthesized nanoparticles were characterized using X‐ray diffraction (XRD), ultraviolet‐visible (UV‐Vis) absorption spectroscopy, Fourier transform infra‐red (FTIR) spectroscopy, and electron microscopy. A plausible mechanism of the formation of gold nanoparticles from Pimenta dioica leaf extract was also proposed. Synthesized AuNPs were found to be safe for human cervical cancer (HeLa) and human embryonic kidney 293 (HEK 293) cell lines established using MTT (3‐(4,5‐dimethylthiozol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide) assay. The potential of the synthesized nanoparticles for the plasmonic sensing of analyte molecule was carried out using the AuNPs as a surface‐enhanced Raman spectroscopy substrate. It was found that the AuNPs enhanced the Raman signal of analyte molecules with an enhancement factor of >105 in comparison to the normal Raman signal measured from the analyte, i. e., without nanoparticles. Further, the synthesized AuNPs showed excellent photoacoustic signal responses (PASR) and found to be the most efficient photoacoustic signal generators. The photothermal performance of these nanoparticles was also carried out. Overall, the findings of this study suggest that in future, these AuNPs could be used as a green alternative to conventionally used in‐vivo theranostic agents.
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