Molecular folding governs switchable singlet oxygen photoproduction in porphyrin-decorated bistable rotaxanes.

Rotaxanes are mechanically interlocked molecules where a ring (macrocycle) is threaded onto a linear molecule (thread). The position of the macrocycle on different stations on the thread can be controlled in response to external stimuli, making rotaxanes applicable as molecular switches. Here we show that bistable rotaxanes based on the combination of a Zn(II) tetraphenylporphyrin photosensitizer, attached to the macrocycle, and a black-hole-quencher, attached to the thread, are capable of singlet oxygen production which can be switched on/off by the addition of base/acid.

Pectin-Coated Plasmonic Nanoparticles for Photodynamic Therapy: Inspecting the Role of Serum Proteins.

Plasmonic metal nanoparticles (NPs) can be used as enhancers of the efficiency of standard photosensitizers (PSs) in photodynamic therapy (PDT). Protein corona, the adsorption layer that forms spontaneously around NPs once in contact with biological fluids, determines to a great extent the efficiency of PDT. In this work, we explore the possibility that pectin-coated Au NPs (Au@Pec NPs) could act as adjuvants in riboflavin (Rf)-based PDT by comparing the photodamage in HeLa cells cultured in the presence and in the absence of the NPs.

Photothermal therapy with silver nanoplates in HeLa cells studied by in situ fluorescence microscopy.

Photothermal therapy (PTT) is a noninvasive treatment for cancer relying on the incorporation of NIR-light absorbing nanomaterials into cells, which upon illumination release heat causing thermally induced cell death. We prove that irradiation of aqueous suspensions of poly(vinylpyrrolidone)-coated silver nanoplates (PVPAgNP) or PVPAgNP in HeLa cells with red or NIR lasers causes a sizeable photothermal effect, which in cells can be visualized with the temperature sensing fluorophore Rhodamine B (RhB) using spinning disk confocal fluorescence microscopy or fluorescence lifetime imaging. Upon red-light irradiation of cells that were incubated with both, RhB and PVPAgNP at concentrations with no adverse effects on cell viability, a substantial heat release is detected.

Riboflavin-Mediated Photooxidation of Gold Nanoparticles and Its Effect on the Inactivation of Bacteria.

Photodynamic inactivation (PDI) of microorganisms, based on the ability of photosensitizers to produce reactive oxygen species (ROS) under adequate irradiation, emerges as a promising technique to face the increasing bacterial resistance to conventional antimicrobials. In this work, we analyze the combined action of Riboflavin (Rf) and pectin-coated gold nanoparticles (PecAuNP) on () and () as suitable PDI strategy. We demonstrate that gold ions can be generated upon Rf-photosensitized oxidation of PecAuNP.

Photodynamic Therapy in HeLa Cells Incubated with Riboflavin and Pectin-coated Silver Nanoparticles.

Riboflavin (Rf) is an endogenous photosensitizer, which can participate in Type I and Type II processes. We have recently shown that the yield of the triplet excited states of Rf is enhanced in the presence of pectin-coated silver nanoparticles (Pec@AgNP) due to formation of a complex between Rf and Pec@AgNP (Rf-Pec@AgNP). Consequently, under aerobic conditions, the amounts of singlet molecular oxygen and superoxide radical anion generated are also larger in the presence of the nanoparticles.

Toward biomedical application of amino-functionalized silicon nanoparticles.

Unlabelled: Silicon blue-emitting nanoparticles (NPs) are promising effectors for photodynamic therapy and radiotherapy, because of their production of reactive oxygen species (ROS) upon irradiation.

Results: Amino-functionalized silicon NPs (NHSiNP) were intrinsically nontoxic below 100 μg/ml in vitro (on two tumor cell lines) and in vivo (zebrafish larvae and embryos). NHSiNP showed a moderate effect as a photosensitizer for photodynamic therapy and reduced ROS generation in radiotherapy, which could be indicative of a ROS scavenging effect.