Non-linear optical response by functionalized gold nanospheres: identifying design principles to maximize the molecular photo-release

Gold Nanoparticles as Photothermal Agent in Cancer Therapy: Theoretical Study of Concentration and Agglomeration Effects on Temperature

One promising cancer therapy is related to the treatment of diseased cells through thermal ablation by an individual or an agglomeration of nanoparticles acting as photothermal agents. The main principle of such a therapy consists in the photo-energy absorption by the nanoparticles and its conversion into heat in order to kill the biological media/cells in the neighboring regions of such a photothermal agent. Nevertheless, such a therapy must preserve the surrounding healthy cells (or biological media). In case of agglomerates of nanoparticles, the local concentrations of nanoparticles may increase the temperature locally. In this paper, we use the finite element method to calculate the temperature elevation for agglomerations of nanoparticles in a biological medium/cell. The positions of nanoparticles, forming the agglomerates, are randomly generated. The temperature elevation for such agglomerations of nanoparticles is then analyzed. We show that the control of the concentration of nanoparticles can preserve the efficiency of the thermal agent, but with limited risk of damage to the surrounding biological media/cells.

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

Photoactivatable (alternatively, photoremovable, photoreleasable, or photocleavable) protecting groups (PPGs), also known as caged or photocaged compounds, are used to enable non-invasive spatiotemporal photochemical control over the release of species of interest. Recent years have seen the development of PPGs activatable by biologically and chemically benign visible and near-infrared (NIR) light. These long-wavelength-absorbing moieties expand the applicability of this powerful method and its accessibility to non-specialist users. This review comprehensively covers organic and transition metal-containing photoactivatable compounds (complexes) that absorb in the visible- and NIR-range to release various leaving groups and gasotransmitters (carbon monoxide, nitric oxide, and hydrogen sulfide). The text also covers visible- and NIR-light-induced photosensitized release using molecular sensitizers, quantum dots, and upconversion and second-harmonic nanoparticles, as well as release via photodynamic (photooxygenation by singlet oxygen) and photothermal effects. Release from photoactivatable polymers, micelles, vesicles, and photoswitches, along with the related emerging field of photopharmacology, is discussed at the end of the review.

Endogenously Triggerable Ultrasmall-in-Nano Architectures: Targeting Assessment on 3D Pancreatic Carcinoma Spheroids

Several nanomaterials rely on the passive accumulation in the neoplasm target because of enhanced permeability and retention effect. On the other hand, directing nanomaterials to the target by employing the targeting agents may lead to a pivotal improvement in the efficacy of the treatment for a number of cancers. However, targeting moieties often lose their functionality upon injection in the bloodstream, leaving questions on their efficiency. Here, we assessed using a significant in vitro 3D model of pancreatic carcinoma the targeting efficiency of passion fruit-like nanoarchitectures (NAs) incorporated with a peptide that can recognize transferrin directly in the medium, thereby modulating protein solvation. NAs are biodegradable ultrasmall-in-nano platforms that combine the most appealing behaviors of noble metal nanomaterials with organism excretion of the building blocks by the renal pathway. Although the confocal images did not illustrate the significant differences in the targeting efficiency of the peptide-modified NAs, an improved internalization was quantitatively observed by inductively coupled plasma-mass spectrometry analysis. Our findings demonstrate that the peptide conjugation of NAs might be considered to enhance their theranostic potentials for this type of neoplasm.

Gold Nanoparticles as a Photothermal Agent in Cancer Therapy: The Thermal Ablation Characteristic Length

In cancer therapy, the thermal ablation of diseased cells by embedded nanoparticles is one of the known therapies. It is based on the absorption of the energy of the illuminating laser by nanoparticles. The resulting heating of nanoparticles kills the cell where these photothermal agents are embedded. One of the main constraints of this therapy is preserving the surrounding healthy cells. Therefore, two parameters are of interest. The first one is the thermal ablation characteristic length, which corresponds to an action distance around the nanoparticles for which the temperature exceeds the ablation threshold. This critical geometric parameter is related to the expected conservation of the body temperature in the surroundings of the diseased cell. The second parameter is the temperature that should be reached to achieve active thermal agents. The temperature depends on the power of the illuminating laser, on the size of nanoparticles and on their physical properties. The purpose of this paper is to propose behavior laws under the constraints of both the body temperature at the boundary of the cell to preserve surrounding cells and an acceptable range of temperature in the target cell. The behavior laws are deduced from the finite element method, which is able to model aggregates of nanoparticles. We deduce sensitivities to the laser power and to the particle size. We show that the tuning of the temperature elevation and of the distance of action of a single nanoparticle is not significantly affected by variations of the particle size and of the laser power. Aggregates of nanoparticles are much more efficient, but represent a potential risk to the surrounding cells. Fortunately, by tuning the laser power, the thermal ablation characteristic length can be controlled.

Ultrasmall-in-Nano Approach: Enabling the Translation of Metal Nanomaterials to Clinics

Currently, nanomaterials are of widespread use in daily commercial products. However, the most-promising and potentially impacting application is in the medical field. In particular, nanosized noble metals hold the promise of shifting the current medical paradigms for the detection and therapy of neoplasms thanks to the: (i) localized surface plasmon resonances (LSPRs), (ii) high electron density, and (iii) suitability for straightforward development of all-in-one nanoplatforms. Nonetheless, there is still no clinically approved noble metal nanomaterial for cancer therapy and diagnostics. The clinical translation of noble metal nanoparticles (NPs) is mainly prevented by the issue of persistence in organism after the medical action. Such persistence increases the likelihood of toxicity and the interference with common medical diagnoses. Size reduction to ultrasmall nanoparticles (USNPs) is a suitable approach to promoting metal excretion by the renal pathway. However, most of the functionalities of NPs are lost or severely altered in USNPs, jeopardizing clinical applications. A ground-breaking advance to jointly combine the appealing behaviors of NPs with metal excretion relies on the ultrasmall-in-nano approach for the design of all-in-one degradable nanoplatforms composed of USNPs. Such nanoarchitectures might lead to the delivery of a novel paradigm for nanotechnology, enabling the translation of noble metal nanomaterials to clinics to treat carcinomas in a less-invasive and more-efficient manner. This Review covers the recent progresses related to this exciting approach. The most-significant nanoarchitectures designed with the ultrasmall-in-nano approach are discussed, and perspectives on these nanoarchitectures are provided.