Simultaneously Enhanced Singlet Oxygen and Fluorescence Production of Nanoplatform by Surface Plasmon Resonance Coupling for Biomedical Applications

211At on gold nanoparticles for targeted radionuclide therapy application

Targeted alpha therapy (TAT) is a methodology that is being developed as a promising cancer treatment using the α-particle decay of radionuclides. This technique involves the use of heavy radioactive elements being placed near the cancer target area to cause maximum damage to the cancer cells while minimizing the damage to healthy cells. Using gold nanoparticles (AuNPs) as carriers, a more effective therapy methodology may be realized. AuNPs can be good candidates for transporting these radionuclides to the vicinity of the cancer cells since they can be labeled not just with the radionuclides, but also a host of other proteins and ligands to target these cells and serve as additional treatment options. Research has shown that astatine and iodine are capable of adsorbing onto the surface of gold, creating a covalent bond that is quite stable for use in experiments. However, there are still many challenges that lie ahead in this area, whether they be theoretical, experimental, and even in real-life applications. This review will cover some of the major developments, as well as the current state of technology, and the problems that need to be tackled as this research topic moves along to maturity. The hope is that with more workers joining the field, we can make a positive impact on society, in addition to bringing improvement and more knowledge to science.

Gold Nanorod/Titanium Dioxide Hybrid Nanoparticles for Plasmon-Enhanced Near-Infrared Photoproduction of Hydroxyl Radicals and Photodynamic Therapy

Gold nanoparticles, such as nanorods (AuNRs), present exceptionally high absorption cross sections that can be tuned to the near-infrared (NIR), the optimal window for light penetration in biological tissues. This makes them valuable photosensitizers for the treatment of cancer using photothermal therapy, where absorbed light energy is converted into heat. In addition, there is a strong interest in using hot electron carriers generated in AuNRs by NIR irradiation to produce cytotoxic radical oxygen species in order to enhance the efficiency of the phototherapy. Here, we show that hybrid nanoparticles composed of AuNRs with TiO2 deposited at their extremities are efficient sensitizers to produce hydroxyl radical species under NIR irradiation. We attribute this phenomenon to the transfer of hot electrons generated from the plasmon excitation in AuNR to the TiO2 tips, followed by reduction of dioxygen. We then functionalize these hybrid AuNR/TiO2 nanoparticles with block poly(ethylene glycol)-phosphonate polymer ligands to stabilize them in a physiological medium. We finally demonstrate that the photodynamic effect induces cell death upon irradiation with a greater efficiency than the photothermal effect alone.

Machine Learning-Aided Design of Gold Core-Shell Nanocatalysts toward Enhanced and Selective Photooxygenation

We demonstrate the use of the machine learning (ML) tools to rapidly and accurately predict the electric field as a guide for designing core-shell Au-silica nanoparticles to enhance ¹O₂ sensitization and selectivity of organic synthesis. Based on the feature importance analysis, obtained from a deep neural network algorithm, we found a general and linear dependent descriptor (θ ∝ aD^0.25t^-1, where a, D, and t are the shape constant, size of metal nanoparticles, and distance from the metal surface) for the electric field around the core-shell plasmonic nanoparticle. Directed by the new descriptor, we synthesized gold-silica nanoparticles and validated their plasmonic intensity using scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) mapping. The nanoparticles with θ = 0.40 demonstrate an ∼3-fold increase in the reaction rate of photooxygenation of anthracene and 4% increase in the selectivity of photooxygenation of dihydroartemisinic acid (DHAA), a long-standing goal in organic synthesis. In addition, the combination of ML and experimental investigations shows the synergetic effect of plasmonic enhancement and fluorescence quenching, leading to enhancement for ¹O₂ generation. Our results from time-dependent density functional theory (TD-DFT) calculations suggest that the presence of an electric field can favor intersystem crossing (ISC) of methylene blue to enhance ¹O₂ generation. The strategy reported here provides a data-driven catalyst preparation method that can significantly reduce experimental cost while paving the way for designing photocatalysts for organic drug synthesis.

Plasmon-Enhanced Photodynamic Therapy for Gastric Cancer by Integrating Targeted Gold Nanorods and Photosensitizer

Gold nanoparticles are widely used for biomedical purposes because of their unique optical, surface plasmon resonance properties, ease of surface functionalization, and high load capacity. Gold nanorods (AuNR), which are rod-shaped gold nanoparticles, have been used as an effective photodynamic treatment (PDT) carrier to boost singlet oxygen (SOG) generation through localized surface plasmon resonance (LSPR) effect and then improve PDT efficacy. However, the suitable spatial location should be established to enable photosensitizer to feel the LSPR enhancement. In this study, we utilized multifunctional PEG chain to adjust efficient distance to induce more photosensitizers to feel the enhanced LSPR effect of AuNR and used a novel gastric tumor angiogenesis marker to prevent the uncontrolled LSPR shift induced by the aggregation of AuNR, and then acquire plasmon-enhanced PDT. The synthesized nano-system of integrated photosensitizer and targeted AuNR could significantly enhance SOG generation and improve the apoptosis-inducing ability through activation of the mitochondria-mediated apoptotic pathway, and -shorten the induction time for apoptosis, thus acquire efficient plasmon-enhanced PDT. Comparing to the normal photosensitizer, half of the targeted photosensitizer produce same antitumor effect, which improves maximum tolerable dose. Generally, this novel targeted delivery system is a promising agent of plasmon-enhanced PDT for gastric cancer.

Drug preconcentration and direct quantification in biofluids using 3D-Printed paper cartridge

Drug detection in biofluids has always been great importance for clinical diagnosis. Many detection technologies such as chromatography-mass spectrometry, have been applied to the detection of drugs. However, these technologies required multi-step operations, including complicated and time-consuming pretreatment processes and operations of bulky detection instruments, significantly limiting development of drug detection in clinical diagnosis. Herein, a portable 3D-printed paper cartridge was fabricated for fast sample preconcentration and direct drugs quantitative detection in biofluids by a portable Raman spectrometer. This cartridge contained both paper tip with silver nanowires to preconcentrate samples and achieve surface-enhanced Raman Scattering (SERS) measurement, and 3D-printed cartridge to build enclosed environment for the improvement of detection, which cost only one dollar. The preconcentration ability of the cartridge was up to 18.13-fold fluorescence enhancement and compared to the non-preconcentration method, it achieved 9.93-fold improvement of SERS performance. The anticancer drug of epirubicin hydrochloride, cyclophosphamide and their mixtures were quantitatively detected in the bovine serum or artificial urine. The integrated detection procedure required only 1 h, including sample pretreatment and preconcentration, drying, SERS measurements, and quantification analysis. This 3D-printed paper cartridge constituted a portable detection platform that would be potentially a practical and point-of-care detection tool for drug preconcentration and quantification on the clinical diagnosis.

Gold Nanostars-AIE Theranostic Nanodots with Enhanced Fluorescence and Photosensitization Towards Effective Image-Guided Photodynamic Therapy

Dual-functional aggregation-induced photosensitizers (AIE-PSs) with singlet oxygen generation (SOG) ability and bright fluorescence in aggregated state have received much attention in image-guided photodynamic therapy (PDT). However, designing an AIE-PS with both high SOG and intense fluorescence via molecular design is still challenging. In this work, we report a new nanohybrid consisting of gold nanostar (AuNS) and AIE-PS dots with enhanced fluorescence and photosensitization for theranostic applications. The spectral overlap between the extinction of AuNS and fluorescence emission of AIE-PS dots (665 nm) is carefully selected using five different AuNSs with distinct localized surface plasmon (LSPR) peaks. Results show that all the AuNSs can enhance the 1O2 production of AIE-PS dots, among which the AuNS with LSPR peak at 585 nm exhibited the highest 1O2 enhancement factor of 15-fold with increased fluorescence brightness. To the best of our knowledge, this is the highest enhancement factor reported for the metal-enhanced singlet oxygen generation systems. The Au585@AIE-PS nanodots were applied for simultaneous fluorescence imaging and photodynamic ablation of HeLa cancer cells with strongly enhanced PDT efficiency in vitro. This study provides a better understanding of the metal-enhanced AIE-PS nanohybrid systems, opening up new avenue towards advanced image-guided PDT with greatly improved efficacy.

Versatile Nanoplatforms with enhanced Photodynamic Therapy: Designs and Applications

As an emerging antitumor strategy, photodynamic therapy (PDT) has attracted intensive attention for the treatment of various malignant tumors owing to its noninvasive nature and high spatial selectivity in recent years. However, the therapeutic effect is unsatisfactory on some occasions due to the presence of some unfavorable factors including nonspecific accumulation of PS towards malignant tissues, the lack of endogenous oxygen in tumors, as well as the limited light penetration depth, further hampering practical application. To circumvent these limitations and improve real utilization efficiency, various enhanced strategies have been developed and explored during the past years. In this review, we give an overview of the state-of-the-art advances progress on versatile nanoplatforms for enhanced PDT considering the enhancement from targeting or responsive, chemical and physical effect. Specifically, these effects mainly include organelle-targeting function, tumor microenvironment responsive release photosensitizers (PS), self-sufficient O2 (affinity oxygen and generating oxygen), photocatalytic water splitting, X-rays light stimulate, surface plasmon resonance enhancement, and the improvement by resonance energy transfer. When utilizing these strategies to improve the therapeutic effect, the advantages and limitations are addressed. Finally, the challenges and prospective will be discussed and demonstrated for the future development of advanced PDT with enhanced efficacy.

Non-powered capillary force-driven stamped approach for directly printing nanomaterials aqueous solution on paper substrate

The recent boom of nanomaterials printing in the fields of biomedical engineering, bioanalysis and flexible electronics has greatly stimulated researchers' interest in printing technologies. However, specifically formulated nanomaterial inks have limited the types of printable nanomaterials. Here, a unique non-powered capillary force-driven stamped (CFDS) approach, combining a 3D-printed stamper with a paper substrate, is developed for directly printing patterned nanomaterials aqueous solution. The CFDS approach has two processes, including the loading process in which the capillary force of the stamper channel is stronger than gravity, and the deposition process, in which the synergistic action of the capillary force of the paper fibre tubes and gravity is approximately 20 times the capillary force of the stamper channel. Four additive-free nanomaterial aqueous solutions, including nanowires, nanosheets, nanostars and nanogels, are used to print patterns, and show slight diffusion and desired uniformity with a diffusion rate and roundness of 1.12 and 0.78, respectively, demonstrating the feasibility of this approach. Four kinds of nanogel with different fluorescence labels are simultaneously printed to challenge the approach and demonstrate its flexibility and scalability. The resolution of the approach is 0.3 mm. Without any post-processing, the stamped paper substrates directly serve as paper-based surface enhanced Raman scattering substrates with an enhancement factor of 4 × 106 and as electrodes with a resistance of 0.74 Ω, demonstrating their multi-functionality. Due to its general, flexible and scalable applicability, this simple, low-cost and non-powered approach could be widely applied to the personalized printing of nanomaterials on paper substrates.