A novel therapeutic strategy of multimodal nanoconjugates for state-of-the-art brain tumor phototherapy

Background The outcome of phototherapy, including photothermal therapy (PTT) and photodynamic therapy (PDT) for glioblastoma multiforme (GBM), is disappointing due to insufficient photoconversion efficiency and low targeting rate. The development of phototherapeutic agents that target GBM and generate high heat and potent ROS is important to overcome the weak anti-tumor effect. Results In this study, nanoconjugates composed of gold nanoparticles (AuNPs) and photosensitizers (PSs) were prepared by disulfide conjugation between Chlorin e6 (Ce6) and glutathione coated-AuNP. The maximum heat dissipation of the nanoconjugate was 64.5 ± 4.5 °C. Moreover, the proximate conjugation of Ce6 on the AuNP surface resulted in plasmonic crossover between Ce6 and AuNP. This improves the intrinsic ROS generating capability of Ce6 by 1.6-fold compared to that of unmodified-Ce6. This process is called generation of metal-enhanced reactive oxygen species (MERos). PEGylated-lactoferrin (Lf-PEG) was incorporated onto the AuNP surface for both oral absorption and GBM targeting of the nanoconjugate (denoted as Ce6-AuNP-Lf). In this study, we explored the mechanism by which Ce6-AuNP-Lf interacts with LfR at the intestinal and blood brain barrier (BBB) and penetrates these barriers with high efficiency. In the orthotopic GBM mice model, the oral bioavailability and GBM targeting amount of Ce6-AuNP-Lf significantly improved to 7.3 ± 1.2% and 11.8 ± 2.1 μg/kg, respectively. The order of laser irradiation, such as applying PDT first and then PTT, was significant for the treatment outcome due to the plasmonic advantages provided by AuNPs to enhance ROS generation capability. As a result, GBM-phototherapy after oral administration of Ce6-AuNP-Lf exhibited an outstanding anti-tumor effect due to GBM targeting and enhanced photoconversion efficiency. Conclusions The designed nanoconjugates greatly improved ROS generation by plasmonic crossover between AuNPs and Ce6, enabling sufficient PDT for GBM as well as PTT. In addition, efficient GBM targeting through oral administration was possible by conjugating Lf to the nanoconjugate. These results suggest that Ce6-AuNP-Lf is a potent GBM phototherapeutic nanoconjugate that can be orally administered. Graphical Abstract

Nanostructured ternary perovskite oxides as photoconversion efficiency enhancers for DSSC

The ternary perovskite oxides are potential candidates as stand-in electron transport layer (ETL) materials to supersede the conventional binary TiO2 in dye-sensitized solar cells (DSSCs). Here, we report the synthesis...

Key parameters of textured silicon solar cells of 26.6% photoconversion efficiency

A new approach to modeling the parameters of high efficiency textured silicon solar cells (SCs) has been presented. Unlike conventional optimization formalisms, our approach additionally includes such important factors as the non-radiative Auger recombination of excitons via deep impurity levels as well as electron-hole pairs recombination in the space charge region. A simple phenomenological expression offered by us earlier for the external quantum efficiency of the textured silicon solar cells with account of the photocurrent in the long-wave part of the absorption spectrum has been also used. Applying this approach, the key parameters of textured silicon SCs, namely: short-circuit current, open-circuit voltage and photoconversion efficiency, have been theoretically determined. The proposed formalism allows calculating the thickness dependence of photoconversion efficiency, which is in good agreement with the experimental results obtained for the heterojunction SCs with the record photoconversion efficiency of 26.6%. The offered approach and the results of applying this phenomenological expression for the external quantum efficiency of the photocurrent in the long-wave part of the absorption spectrum can be used to optimize the characteristics of high efficiency textured SCs based on monocrystalline silicon.

How Can the Introduction of Zr4+ Ions into TiO2 Nanomaterial Impact the DSSC Photoconversion Efficiency? A Comprehensive Theoretical and Experimental Consideration

A series of pure and doped TiO2 nanomaterials with different Zr4+ ions content have been synthesized by the simple sol-gel method. Both types of materials (nanopowders and nanofilms scratched off of the working electrode’s surface) have been characterized in detail by XRD, TEM, and Raman techniques. Inserting dopant ions into the TiO2 structure has resulted in inhibition of crystal growth and prevention of phase transformation. The role of Zr4+ ions in this process was explained by performing computer simulations. The three structures such as pure anatase, Zr-doped TiO2, and tetragonal ZrO2 have been investigated using density functional theory extended by Hubbard correction. The computational calculations correlate well with experimental results. Formation of defects and broadening of energy bandgap in defected Zr-doped materials have been confirmed. It turned out that the oxygen vacancies with substituting Zr4+ ions in TiO2 structure have a positive influence on the performance of dye-sensitized solar cells. The overall photoconversion efficiency enhancement up to 8.63% by introducing 3.7% Zr4+ ions into the TiO2 has been confirmed by I-V curves, EIS, and IPCE measurements. Such efficiency of DSSC utilizing the working electrode made by Zr4+ ions substituted into TiO2 material lattice has been for the first time reported.