Nanocomposites of Molybdenum Disulfide/Methoxy Polyethylene Glycol-<i>co</i>-Polypyrrole for Amplified Photoacoustic Signal

Photoacoustic activity is the generation of an ultrasonic signal via thermal expansion or bubble formation, stimulated by laser irradiation. Photoacoustic nanoplatforms have recently gained focus for application in bioelectric interfaces. Various photoacoustic material types have been evaluated, including gold nanoparticles, semiconductive π-conjugating polymers (SP), etc. In this study, surfactant-free methoxy-polyethylene glycol-<i>co</i>-polypyrrole copolymer (mPEG-<i>co</i>-PPyr) nanoparticles (NPs) and mPEG-<i>co</i>-PPyr NP/molybdenum disulfide (mPEG-<i>co</i>-PPyr/MoS₂) nanocomposites (NCs) were prepared and their photoacoustic activity was demonstrated. The mPEG-<i>co</i>-PPyr NPs and mPEG-<i>co</i>-PPyr/MoS₂ NCs both showed photoacoustic signal activity. The mPEG-<i>co</i>-PPyr/MoS₂ NCs presented a higher photoacoustic signal amplitude at 700 nm than the mPEG-<i>co</i>-PPyr NPs. The enhanced photoacoustic activity of the mPEG-<i>co</i>-PPyr/MoS₂ NCs might be attributed to heterogeneous interfacial contact between mPEG-<i>co</i>-PPyr and the MoS₂ nanosheets due to complex formation. Laser ablation of MoS₂ might elevate the local temperature and facilitate the thermal conductive transfer in the mPEG-<i>co</i>-PPyr/MoS₂ NCs, amplifying PA signal. Our study, for the first time, demonstrates enhanced PA activity in SP/transition metal disulfide (TMD) composites as photoacoustic nanoplatforms

Amplified Photoacoustic Performance and Enhanced Photothermal Stability of Reduced Graphene Oxide Coated Gold Nanorods for Sensitive Photoacoustic Imaging

We report a strongly amplified photoacoustic (PA) performance of the new functional hybrid material composed of reduced graphene oxide and gold nanorods. Due to the excellent NIR light absorption properties of the reduced graphene oxide coated gold nanorods (r-GO-AuNRs) and highly efficient heat transfer process through the reduced graphene oxide layer, r-GO-AuNRs exhibit excellent photothermal stability and significantly higher photoacoustic amplitudes than those of bare-AuNRs, nonreduced graphene oxide coated AuNRs (GO-AuNRs), or silica-coated AuNR, as demonstrated in both <i>in vitro</i> and <i>in vivo</i> systems. The linear response of PA amplitude from reduced state controlled GO on AuNR indicates the critical role of GO for a strong photothermal effect of r-GO-AuNRs. Theoretical studies with finite-element-method lab-based simulation reveal that a 4 times higher magnitude of the enhanced electromagnetic field around r-GO-AuNRs can be generated compared with bare AuNRs or GO-AuNRs. Furthermore, the r-GO-AuNRs are expected to be a promising deep-tissue imaging probe because of extraordinarily high PA amplitudes in the 4–11 MHz operating frequency of an ultrasound transducer. Therefore, the r-GO-AuNRs can be a useful imaging probe for highly sensitive photoacoustic images and NIR sensitive therapeutics based on a strong photothermal effect