Photosensitiser functionalised luminescent upconverting nanoparticles for efficient photodynamic therapy of breast cancer cells.

Photodynamic therapy (PDT) is a well-established treatment of cancer in which cell toxic reactive oxygen species, including singlet oxygen (1O2), are produced by a photosensitiser drug following irradiation of a specific wavelength. Visible light is commonly used as the excitation source in PDT, although these wavelengths do have limited tissue penetration. In this research, upconverting nanoparticles (UCNPs) functionalised with the photosensitiser Rose Bengal (RB) have been designed and synthesised for PDT of breast cancer cells. The use of UCNPs shifts the required excitation wavelength for the production of 1O2 to near infrared light (NIR) thus allowing deeper tissue penetration. The system was designed to maximise the production of 1O2via efficient Förster resonance energy transfer (FRET) from the UCNPs to the photosensitiser. Highly luminescent NaYF4:Yb,Er,Gd@NaYF4 core-shell UCNPs were synthesised that exhibited two main anti-Stokes emission bands at 541 and 652 nm following 980 nm irradiation. RB was chosen as the photosensitiser since its absorption band overlaps with the green emission of the UCNPs. To achieve efficient energy transfer from the nanoparticles to the photosensitiser, the functionalised UCNPs included a short l-lysine linker to attach the RB to the nanocore yielding RB-lysine functionalised UCNPs. The efficient FRET from the UCNPs to the RB was confirmed by luminescence lifetime measurements. The light emitted by the UCNPs at 541 nm, following excitation at 980 nm, generates the 1O2via the RB. Multi-photon and confocal laser scanning microscopies confirmed the internalisation of the RB-lysine-UCNPs by SK-BR-3 breast cancer cells. Cell viability studies revealed that the RB-lysine-UCNPs induced low dark toxicity in cells prior to PDT treatment. Importantly, following irradiation at 980 nm, high levels of cell death were observed in cells loaded with the RB-lysine-UCNPs. Cell death following PDT treatment was also confirmed using propidium iodide and confocal microscopy. The high drug loading capacity (160 RB/nanoparticle) of the UCNPs, the efficient FRET from the UCNPs to the photosensitiser, the high level of accumulation inside the cells and their PDT cell kill suggest that the RB-lysine-UCNPs are promising for NIR PDT and hence suitable for the treatment of deep-lying cancer tumours.

Photosensitiser-gold nanoparticle conjugates for photodynamic therapy of cancer.

Gold nanoparticles (AuNPs) have been extensively studied within biomedicine due to their biocompatibility and low toxicity. In particular, AuNPs have been widely used to deliver photosensitiser agents for photodynamic therapy (PDT) of cancer. Here we review the state-of-the-art for the functionalisation of the gold nanoparticle surface with both photosensitisers and targeting ligands for the active targeting of cancer cell surface receptors. From the initial use of the AuNPs as a simple carrier of the photosensitiser for PDT, the field has significantly advanced to include: the use of PEGylated modification to provide aqueous compatibility and stealth properties for in vivo use; gold metal-surface enhanced singlet oxygen generation; functionalisation of the AuNP surface with biological ligands to specifically target over-expressed receptors on the surface of cancer cells and; the creation of nanorods and nanostars to enable combined PDT and photothermal therapies. These versatile AuNPs have significantly enhanced the efficacy of traditional photosensitisers for both in vitro and in vivo cancer therapy. From this review it is apparent that AuNPs have an important future in the treatment of cancer.

Targeted photodynamic therapy of breast cancer cells using lactose-phthalocyanine functionalized gold nanoparticles.

Gold nanoparticles (AuNPs), which have been widely used for the delivery of photosensitizers for photodynamic therapy (PDT) of cancer, can be dispersed in aqueous solutions improving the delivery of the hydrophobic photosensitizer into the body. Furthermore, the large surface of AuNPs can be functionalized with a variety of ligands, including proteins, nucleic acids and carbohydrates, that allow selective targeting to cancer tissue. In this study, gold nanoparticles were functionalized with a mixed monolayer of a zinc phthalocyanine and a lactose derivative. For the first time, a carbohydrate was used with a dual purpose, as the stabilizing agent of the gold nanoparticles in aqueous solutions and as the targeting agent for breast cancer cells. The functionalization of the phthalocyanine-AuNPs with lactose led to the production of water-dispersible nanoparticles that are able to generate singlet oxygen and effect cell death upon irradiation. The targeting ability of lactose of the lactose-phthalocyanine functionalized AuNPs was studied in vitro towards the galectin-1 receptor on the surface of breast cancer cells. The targeting studies showed the exciting potential of lactose as a specific targeting agent for galactose-binding receptors overexpressed on breast cancer cells.

Towards optimisation of surface enhanced photodynamic therapy of breast cancer cells using gold nanoparticle-photosensitiser conjugates.

Gold nanoparticles (AuNPs; ca. 4 nm) were synthesised and functionalised with a mixed monolayer of polyethylene glycol (PEG) and one of two zinc phthalocyanines (ZnPcs), the difference between the two molecules was the length of the carbon chain that connects the Pc to the gold core. The chain was composed of either three (C3Pc) or eleven (C11Pc) carbon atoms. The C11Pc photosensitiser displayed higher fluorescence emission intensity than the C3Pc in solution. By contrast, the C3Pc photosensitiser exhibited higher fluorescence when bound to the surface of the AuNPs than the C11Pc, despite the shorter carbon chain which was expected to quench the fluorescence. In addition, the C3Pc nanoparticle conjugates exhibited an enhancement in the production of singlet oxygen (1O2). The metal-enhanced 1O2 production led to a remarkable photodynamic efficacy for the treatment of human breast cancer cells.