RESUMEN
Gas-liquid interfaces are reaching a particular interest in biomedicine. Microbubbles, ultrasound contrast agents of clinical routine, gained increasing attention as theranostic platforms due to the preserved acoustic response, drug conjugation capabilities, and applicability in biological barrier opening. A combination of microbubbles and photodynamic therapy agents can enhance the photodynamic effect, yet the evaluation of agent conjugation on microbubble stabilization and photodynamic effect is needed. Hence, two commercially available phthalocyanine photosensitizers - Holosens® (ZnPc) and Photosens® (AlPc) - were coupled with bovine serum albumin before microbubble synthesis. We demonstrated an albumin: phthalocyanine ratio of 1:1 and covalent attachment for ZnPc, a ratio of 1:3 with electrostatic binding for AlPc. Submicron-sized microbubbles (air- and SF6- filled) had a diameter of 0.8 µm. Albumin-phthalocyanine conjugates increased the microbubble concentration and shelf-life stability compared to plain ones. We hypothesized that phthalocyanine fluorescence lifetime values decreased after conjugation with microbubbles due to narrow distance between conjugates in the shell. Agents based on AlPc demonstrated higher photodynamic activity than agents based on ZnPc, and microbubbles preserved acoustic stability in human blood plasma. The biodistribution of AlPc-conjugated microbubbles was evaluated. We conclude that our microbubble platforms demonstrate greater photodynamic activity and prolonged stability for further applications in photodynamic therapy.
RESUMEN
Microbubbles are intravascular contrast agents clinically used in diagnostic sonography, echocardiography, and radiology imaging applications. However, up to date, the idea of creating microbubbles with multiple functionalities (e.g., multimodal imaging, photodynamic therapy) remained a challenge. One possible solution is the modification of bubble shells by introducing specific compounds responsible for such functions. In the present work, air-core microbubbles with the shell consisting of bovine serum albumin, albumin-coated gold nanocages, and zinc phthalocyanine were prepared using the sonication method. Various physicochemical parameters such as stability over time, size, and concentration were investigated to prove the potential use of these microbubbles as contrast agents. This work shows that hybrid microbubbles have all the necessary properties for multimodal imaging (ultrasound, raster-scanning microscopy, and fluorescence tomography), which demonstrate superior characteristics for potential theranostic and related biomedical applications.
RESUMEN
Microbubbles have already reached clinical practice as ultrasound contrast agents for angiography. However, modification of the bubbles' shell is needed to produce probes for ultrasound and multimodal (fluorescence/photoacoustic) imaging methods in combination with theranostics (diagnostics and therapeutics). In the present work, hybrid structures based on microbubbles with an air core and a shell composed of bovine serum albumin, albumin-coated gold nanoparticles, and clinically available photodynamic dyes (zinc phthalocyanine, indocyanine green) were shown to achieve multimodal imaging for potential applications in photodynamic therapy. Microbubbles with an average size of 1.5 ± 0.3 µm and concentration up to 1.2 × 109 microbubbles/mL were obtained and characterized. The introduction of the dye into the system reduced the solution's surface tension, leading to an increase in the concentration and stability of bubbles. The combination of gold nanoparticles and photodynamic dyes' influence on the fluorescent signal and probes' stability is described. The potential use of the obtained probes in biomedical applications was evaluated using fluorescence tomography, raster-scanning optoacoustic microscopy and ultrasound response measurements using a medical ultrasound device at the frequency of 33 MHz. The results demonstrate the impact of microbubbles' stabilization using gold nanoparticle/photodynamic dye hybrid structures to achieve probe applications in theranostics.
RESUMEN
A layered perovskite-type oxide intercalated with n-butylamine is reported as an efficient photocatalyst for hydrogen production from aqueous solutions of alcohols for the first time. The hybrid photocatalyst H2Nd2Ti3O10×BuNH2 was synthesized by solid-state ceramic method followed by protonation, intercalation of methylamine and subsequent substitution by n-butylamine. The product was characterized by powder XRD, TGA, STA-MS, DRS, IR, and Raman spectroscopy, CHN analysis, SEM. Intercalation of n-butylamine caused a dramatic increase in photocatalytic activity of H2Nd2Ti3O10 in the reaction of hydrogen evolution from aqueous solutions of methanol, ethanol, and n-butanol under UV radiation. While the non-intercalated Pt-loaded H2Nd2Ti3O10 showed a maximum quantum efficiency of only 2% in the 220-340 nm range, the efficiency for hybrid samples reached 23% under the same conditions and after variation of experimental parameters even 52% efficiency was achieved. This effect may be associated with the significant expansion of the interlayer space, which is considered as a separate reaction zone.
