Effect of the Materials Properties of Hydroxyapatite Nanoparticles on Fibronectin Deposition and Conformation

Hydroxyapatite (HAP, Ca₁₀(PO₄)₆(OH)₂) nanoparticles with controlled materials properties have been synthesized through a two-step hydrothermal aging method to investigate fibronectin (Fn) adsorption. Two distinct populations of HAP nanoparticles have been generated: HAP1 particles had smaller size, plate-like shape, lower crystallinity, and more negative ζ potential than HAP2 particles. We then developed two-dimensional platforms containing HAP and Fn and analyzed both the amount and the conformation of Fn via Förster resonance energy transfer (FRET) at various HAP concentrations. Our FRET analysis reveals that larger amounts of more compact Fn molecules were adsorbed onto HAP1 than onto HAP2 particles. Additionally, our data show that the amount of compact Fn adsorbed increased with increasing HAP concentration due to the formation of nanoparticle agglomerates. We propose that both the surface chemistry of single nanoparticles and the size and morphology of HAP agglomerates play significant roles in the interaction of Fn with HAP. Collectively, our findings suggest that the HAP-induced conformational changes of Fn, a critical mechanotransducer protein involved in the communication of cells with their environment, will ultimately affect downstream cellular behaviors. These results have important implications for our understanding of organic–inorganic interactions in physiological and pathological biomineralization processes such as HAP-related inflammation

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

Representative case from ex vivo experiments with core specimens of breast tissue included in the microcalcification group (case #2).

<p>Specimen mammography (A) and photoacoustic images obtained from both 700 nm (B) and 800 nm (C) wavelengths were reconstructed with comparable configurations in both directions (top-down and lateral views). The locations of photoacoustic signals were well matched with microcalcifications observed in specimen mammography. The photoacoustic image at 800 nm (C) showed decreasing photoacoustic signal intensities in the region confirmed as microcalcifications through specimen mammography compared with the photoacoustic image at 700 nm (B). The mean value of PAI ratio^† from region of interest was 2.80. Abbreviations: PAI ratio, calculated ratio of the amplitude occurring at the 700 nm wavelength section to that occurring at the 800 nm wavelength section.</p

Multiple regression analysis in the microcalcification group (n = 11) to find factors that contribute to PAI ratios.

<p>*Malignant result according to the pathology report.</p>†<p>Median value of calcification-foci in the core.</p><p>Abbreviations: PAI ratio, calculated ratio of the amplitude occurring at the 700 nm wavelength section to that occurring at the 800 nm wavelength section.</p

Diagram demonstrates experimental arrangement (A) to acquire photoacoustic signal images from 8-gauge core-biopsied breast specimens (B).

<p>To obtain 3-dimensional photoacoustic data, the probe was mechanically moved along the frame scanning direction (B).</p

Results of blind review to assume calcification on PAI.

<p>Abbreviations: PAI, photoacoustic Imaging.</p

PAI ratios from regions of interest within each core.

<p>Abbreviations: PAI ratio, calculated ratio of the amplitude occurring at the 700 nm wavelength section to that occurring at the 800 nm wavelength section.</p

Representative case from ex vivo experiments with core specimens of breast tissue included in the control group (case #5).

<p>Specimen mammography (A) and photoacoustic images (B, C) were reconstructed with comparable configurations in both directions (top-down and lateral views). The photoacoustic image at 800 nm (C) shows constant photoacoustic signal intensities from an unidentified target compared with the photoacoustic image at 700 nm (B). The signal foci in the region of interest are assumed to be in the core. All these foci show constant photoacoustic intensities. The mean value of PAI ratio^† from region of interest within this core was 1.21. The other bright signal foci around the core may be photoacoustic signals from the interfaces between the surfaces of specimen and the gel pad, which show grossly constant photoacoustic signal intensities. Abbreviations: PAI ratio, calculated ratio of the amplitude occurring at the 700 nm wavelength section to that occurring at the 800 nm wavelength section.</p

Change in mean values of the maximum photoacoustic signals at the 700 nm and 800 nm wavelength sections in the control and microcalcification group.

<p>Change in mean values of the maximum photoacoustic signals at the 700 nm and 800 nm wavelength sections in the control and microcalcification group.</p

A 43-year-old male underwent total thyroidectomy due to thyroid cancer.

<p>A specimen radiograph (a) showed a mass with diffuse punctate calcifications in the left thyroid gland and no discernable calcifications in the right thyroid gland. To verify calcifications on photoacoustic imaging, two thyroid tissues from different lobes were obtained from thyroid specimens, with tissue from the left lobe containing compact punctate calcifications and tissue from the right lobe not containing any calcifications (two square boxes). The tissues were retrieved from the specimen without disturbing pathologic diagnosis. A specimen radiograph (b) showed punctate microcalcifications (arrows) acquired from the left thyroid gland and no calcifications acquired from the right thyroid gland. The texture analysis was conducted for the selected region-of-interests (ROIs) indicated by the white boxes in PA images (c) at 700-nm lasing wavelength. Note that the clustered hyperreactive PA signals suspected from the blood coagulations (white arrows) were excluded in the texture analysis, which can also be found on the corresponding photographs (d). In visual assessment of PA image, the ROI of the right resected tissue with microcalcifications contains more PA signals than that of the left resected tissue without microcalcifications. Although the mean value of samples from the left thyroid gland was higher than that of those from the right thyroid gland on specimen US, the mean value of samples from the right thyroid gland was higher than that of the left thyroid gland on both photoacoustic images. There were psammoma bodies from a left resected tissue and no psammoma bodies (arrows) (H&E; X100) from a right resected tissue on pathology (e).</p