Combinational Chemotherapy and Photothermal Therapy Using a Gold Nanorod Platform for Cancer Treatment

Multimodal approaches combined with various nanomaterials and advanced techniques have been developed for synergistic cancer treatment. Among various therapies, conventional chemotherapy (CHT) is a direct cancer treatment that can produce unintended side effects due to nonspecific action on both the tumor and normal cells; patient-friendly photothermal therapy (PTT) may be able to treat embedded tumors in vital regions with minimal invasion but does not guarantee complete removal of cancers. However, the combination of CHT-PTT may provide a promising tool for direct cancer treatment with minimal side effects. In this regard, nanostructured materials, such as gold nanorods with tuned size and surface characteristics, are key components designed to enhance the heating capacity and active or passive delivery of drugs to the tumor site. In this review, the pioneering work synergizing CHT and PTT is summarized, and the current state-of-the-art in the development of inorganic and organic nanocomposites for combinational therapy is described.     

Synthesis and characterisation of luminescent rhenium tricarbonyl complexes with axially coordinated 1,2,3-triazole ligands

A series of 1-alkyl-4-aryl-1,2,3-triazoles (1-methyl-4-phenyl-1,2,3-triazole (1a); 1-propyl-4-phenyl-1,2,3-triazole (1b); 1-benzyl-4-phenyl-1,2,3-triazole (1c); 1-propyl-4-p-tolyl-1,2,3-triazole (1d)) have been prepared through a one-pot procedure involving in situ generation of the alkyl azide from a halide precursor followed by copper catalysed alkyne/azide cycloaddition (CuAAC) with the appropriate aryl alkyne. Cationic Re(I) complexes [Re(bpy)(CO)(3)(1a-d)]PF(6) (2a-d) were then prepared by stirring [Re(bpy)(CO)(3)Cl] with AgPF(6) in dichloromethane in the presence of ligands 1a-d. X-ray crystal structures were obtained for 2a and 2b. In the solid state, 2a adopts a highly distorted geometry, which is not seen for 2b, in which the plane of the triazole ligand tilts by 13° with respect to the Re-N bond as a result of a π-stacking interaction between the Ph substituent and one of the rings of the bpy ligand. This π-stacking interaction also results in severe twisting of the bpy ligand. Infrared spectra of 2a-d exhibit ν(CO) bands at ～2035 and ～1926 cm(-1) suggesting that these ligands are marginally better donors than pyridine (ν(CO) = 2037, 1932 cm(-1)). The complexes are luminescent in aerated dichloromethane at room temperature with emission maxima at 542 to 552 nm comparable to that of the pyridine analogue (549 nm) and blue shifted relative to the parent chloride complex. Long luminescent lifetimes are observed for the triazole complexes (475 to 513 ns) in aerated dichloromethane solutions at room temperature.     

Synthesis, characterisation and theoretical study of ruthenium 4,4'-bi-1,2,3-triazolyl complexes: fundamental switching of the nature of S1 and T1 states from MLCT to MC

The series of complexes [Ru(bpy)(3-n)(btz)(n)][PF(6)](2) (bpy = 2,2'-bipyridyl, btz = 1,1'-dibenzyl-4,4'-bi-1,2,3-triazolyl, 2n = 1, 3n = 2, 4n = 3) have been prepared and characterised, and the photophysical and electronic effects imparted by the btz ligand were investigated. Complexes 2 and 3 exhibit MLCT absorption bands at 425 and 446 nm respectively showing a progressive blue-shift in the absorption on increasing the btz ligand content when compared to [Ru(bpy)(3)][Cl](2) (1). Complex 4 exhibits a heavily blue-shifted absorption spectrum with respect to those of 1-3, indicating that the LUMO of the latter are bpy-centred with little or no btz contribution whereas that of 4 is necessarily btz-centred. DFT calculations on analogous complexes 1'-4' (in which the benzyl substituents are replaced by methyl) show that the HOMO-LUMO gap increases by 0.3 eV from 1'-3' through destabilisation of the LUMO with respect to the HOMO. The HOMO-LUMO gap of 4' increases by 0.98 eV compared to that of 3' due to significant destabilisation of the LUMO. Examination of TDDFT data show that the S(1) states of 1'-3' are (1)MLCT in character whereas that of 4' is (1)MC. The optimisation of the T(1) state of 4' leads to the elongation of two mutually trans Ru-N bonds to yield [Ru(κ(2)-btz)(κ(1)-btz)(2)](2+), confirming the (3)MC character. Thus, replacement of bpy by btz leads to a fundamental change in the ordering of excited states such that the nature of the lowest energy excited state changes from MLCT in nature to MC.     

Study of the thermal decomposition of flame-retarded unsaturated polyester resins by thermogravimetric analysis and Py-GC/MS

The thermal degradation behaviours of flame-retarded unsaturated polyester resin formulations containing ammonium polyphosphate (APP), Cloisite 25A nanoclay and zinc based smoke suppressants have been studied using thermogravimetric analysis (TGA) combined with infrared analysis of the evolved gases (EGA) and pyrolysis/gas chromatography-mass spectrometry (GC/MS). In TGA-EGA experiments, the mass loss as a function of temperature has been correlated with the evolution of carbon monoxide (CO) and carbon dioxide (CO₂) and oxygen (O₂) consumption as measured by an oxygen analyser. The effect of APP, Cloisite 25A and the smoke suppressants on the evolution of CO and CO₂ has been examined. The decomposition behaviour of flame-retarded polyester resins under isothermal pyrolytic conditions was investigated and the evolved gaseous products were collected and qualitatively and semi-quantitatively analysed via GC/MS. The addition of APP does not yield many new gaseous products relative to the unmodified polyester resin neither does the presence of zinc borate (ZB) and zinc stannate (ZS) together with APP. Possible chemical interactions are discussed in an attempt to explain the observed results.     

Effects of Water and Chemical Solutions Ageing on the Physical,Mechanical, Thermal and Flammability Properties of Natural Fibre-Reinforced Thermoplastic Composites

Biocomposites comprising a combination of natural fibres and bio-based polymers are good alternatives to those produced from synthetic components in terms of sustainability and environmental issues. However, it is well known that water or aqueous chemical solutions affect natural polymers/fibres more than the respective synthetic components. In this study the effects of water, salt water, acidic and alkali solutions ageing on water uptake, mechanical properties and flammability of natural fibre-reinforced polypropylene (PP) and poly(lactic acid) (PLA) composites were compared. Jute, sisal and wool fibre- reinforced PP and PLA composites were prepared using a novel, patented nonwoven technology followed by the hot press method. The prepared composites were aged in water and chemical solutions for up to 3 week periods. Water absorption, flexural properties and the thermal and flammability performances of the composites were investigated before and after ageing each process. The effect of post-ageing drying on the retention of mechanical and flammability properties has also been studied. A linear relationship between irreversible flexural modulus reduction and water adsorption/desorption was observed. The aqueous chemical solutions caused further but minor effects in terms of moisture sorption and flexural modulus changes. PLA composites were affected more than the respective PP composites, because of their hydrolytic sensitivity. From thermal analytical results, these changes in PP composites could be attributed to ageing effects on fibres, whereas in PLA composite changes related to both those of fibres present and of the polymer. Ageing however, had no adverse effect on the flammability of the composites.     

Flammability, degradation and structural characterization of fibre-forming polypropylene containing nanoclay-flame retardant combinations

We have shown previously that the introduction of nanoclays can reduce the flammability of synthetic fibre-forming polymers like polyamides 6 and 6.6 only if used in conjunction with conventional flame retardants. In this work we report initial studies of the effects of dispersed nanoclays with low concentrations of selected flame retardants introduced into polypropylene on flammability, thermal degradation and X-ray diffraction behaviours. Flame retardants used include ammonium polyphosphate as a conventional char-former and a hindered amine stabiliser known to have flame retarding characteristics in polypropylene.