Fluorescence quenching of meso-tetrakis (4-sulfonatophenyl) porphyrin by colloidal TiO(2)

Porphyrin-Gold Nanomaterial for Efficient Drug Delivery to Cancerous Cells

With an aim to overcome multidrug resistance (MDR), nontargeted delivery, and drug toxicity, we developed a new nanochemotherapeutic system with tetrasodium salt of meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) armored on gold nanoparticles (TPPS-AuNPs). The nanocarrier is able to be selectively internalized within tumor cells than in normal cells followed by endocytosis and therefore delivers the antitumor drug doxorubicin (DOX) particularly to the nucleus of diseased cells. The embedment of TPPS on the gold nanosurface provides excellent stability and biocompatibility to the nanoparticles. Porphyrin interacts with the gold nanosurface through the coordination interaction between gold and pyrrolic nitrogen atoms of the porphyrin and forms a strong association complex. DOX-loaded nanocomposite (DOX@TPPS-AuNPs) demonstrated enhanced cellular uptake with significantly reduced drug efflux in MDR brain cancer cells, thereby increasing the retention time of the drug within tumor cells. It exhibited about 9 times greater potency for cellular apoptosis via triggered release commenced by acidic pH. DOX has been successfully loaded on the porphyrin-modified gold nanosurface noncovalently with high encapsulation efficacy (∼90%) and tightly associated under normal physiological conditions but capable of releasing ∼81% of drug in a low-pH environment. Subsequently, DOX-loaded TPPS-AuNPs exhibited higher inhibition of cellular metastasis, invasion, and angiogenesis, suggesting that TPPS-modified AuNPs could improve the therapeutic efficacy of the drug molecule. Unlike free DOX, drug-loaded TPPS-AuNPs did not show toxicity toward normal cells. Therefore, higher drug encapsulation efficacy with selective targeting potential and acidic-pH-mediated intracellular release of DOX at the nucleus make TPPS-AuNPs a "magic bullet" for implication in nanomedicine.

Use of Spectroscopic Techniques for Evaluating the Coupling of Porphyrins on Biocompatible Nanoparticles. A Potential System for Photodynamics, Theranostics, and Nanodrug Delivery Applications

Modern medicine has been searching for new and more efficient strategies for diagnostics and therapeutics applications. Considering this, porphyrin molecules have received great interest for applications in photodiagnostics and phototherapies, even as magnetic nanoparticles for drug-delivery systems and magnetic-hyperthermia therapy. Aiming to obtain a multifunctional system, which combines diagnostics with therapeutic functions on the same platform, the present study employed UV/vis absorption and fluorescence spectroscopies to evaluate the interaction between meso-tetrakis(p-sulfonatofenyl)porphyrin (TPPS) and maghemite nanoparticles (γ-Fe₂O₃). These spectroscopic techniques allowed us to describe the dynamics of coupling porphyrins on nanoparticles and estimate the number of 21 porphyrins per nanoparticle. Also, the binding parameters, such as the association constants (K_a = 8.89 × 10⁵ M^-1) and bimolecular quenching rate constant (k_q = 2.54 × 10¹⁴ M^-1 s^-1) were obtained. These results suggest a static quenching process where the electrostatic attraction plays an essential role. The work shows that spectroscopic techniques are powerful tools to evaluate the coupling of organic molecules and nanoparticles. Besides, the system studied provides a relevant background for potential applications in bionanotechnology and nanomedicine, such as (1) nanodrug delivery system, (2) photodiagnostics/theranostics, and/or (3) a combined action of photodynamic and hyperthermia therapies, working in a synergetic way.

In Situ Generation of Electron Donor to Assist Signal Amplification on Porphyrin-Sensitized Titanium Dioxide Nanostructures for Ultrasensitive Photoelectrochemical Immunoassay

An ultrasensitive photoelectrochemical (PEC) immunoassay protocol for quantitative detection of low-abundant proteins at a low potential was designed by utilizing porphyrin-sensitized titanium dioxide (TiO2) nanostructures. Experimental results demonstrated that the water-soluble 5,10,15,20-tetra(4-sulfophenyl)-21H,23H-porphyrin (TSPP) could be bound onto titanium dioxide via the sulfonic group. TSPP-sensitized TiO2 nanostructures exhibited better photoelectrochemical responses and stability in comparison with TiO2 nanoparticles alone under continuous illumination. Using carcinoembryonic antigen (CEA) as a model analyte, a typical PEC immunosensor by using TSPP-TiO2 as the affinity support of anti-CEA capture antibody (Ab1) to facilitate the improvement of photocurrent response was developed. Bioconjugates of secondary antibody and glucose oxidase with gold nanoparticles (Ab2/GOx-AuNPs) was introduced by an antigen-antibody immunoreaction. AuNP acted as a powerful scaffold to bind with bioactive molecules, while GOx catalyzed glucose to in situ generate hydrogen peroxide (H2O2). The generated H2O2 as a sacrificial electron donor could be oxidized by the photogenerated holes to assist the signal amplification at a low potential under light excitation, thus eliminating interference from other species coexisting in the samples. Under optimal conditions, the PEC immunosensor showed a good linear relationship ranging from 0.02 to 40 ng mL(-1) with a low detection limit of 6 pg mL(-1) CEA. The precision, reproducibility, and specificity were acceptable. In addition, the method accuracy was also evaluated for quantitatively monitoring human serum samples, giving results matching with the referenced CEA ELISA kit.

Electron transfer and fluorescence “turn-off” based CdTe quantum dots for vancomycin detection at nanogram level in aqueous serum media

Mode of interaction of GSH-CdTe QDs with vancomycin and the mechanism of the fluorescence “turn-off” process.

Contrasting emission behaviour of phenanthroimidazole with ZnO nanoparticles

A new fluorophore 2-(4-fluorophenyl)-1-phenyl-1H-phenanthro [9,10-d]imidazole has been synthesized and characterized by spectroscopic techniques. Nanoparticulate ZnO enhances the fluorescence of the synthesised fluorophore. The absorption, fluorescence, lifetime, cyclic voltammetry and infrared studies reveal that fluorophore is attached to the surface of ZnO semiconductor. Photo-induced electron transfer (PET) explains the enhancement of fluorescence by nanoparticulate ZnO and the apparent binding constant has been obtained. Adsorption of the fluorophore on ZnO nanoparticle lowers the HOMO and LUMO energy levels of the fluorophore. The strong adsorption of the phenanthrimidazole derivative on the surface of ZnO nanocrystals is likely due to the chemical affinity of the nitrogen atom of the organic molecule to the zinc ion on the surface of nanocrystal.

Benzimidazole derivative vs. different phases of TiO2-physico-chemical approach

1-Benzyl-2-phenyl-1H-benzo[d]imidazole (BPBI) has been synthesized by simple steps and characterized by spectral studies. Absorption and fluorescence spectral studies have been employed to investigate the interaction of BPBI with the anatase, hombikat, P25 and rutile phases of TiO2. The emission of the BPBI is efficiently quenched by anatase, hombikat and P25 TiO2 nanoparticles owing to charge injection from the excited singlet state of BPBI to the conduction band of the TiO2 nanoparticles. Surprisingly, rutile phase enhances the fluorescence which is likely due to lowering of LUMO and HOMO levels of the ligand on ducking of the benzimidazole moiety of the BPBI molecule into the void space of rutile TiO2. Electron injection from photoexcited BPBI to the TiO2 conduction band (S*→S(+)+e(-)(CB)) is likely to enhance the fluorescence.

Fluorescence quenching of organic molecule by insulator

A new kind of fluorophore 2-(4-fluorophenyl)-1-phenyl-1H-benzo[d]imidazole (FPPBI) has been synthesized and characterized by (1)H NMR, (13)C NMR, mass spectral studies and single crystal XRD. The energy transfer from FPPBI to Al2O3 nanocrystals has been studied by absorption, fluorescence and lifetime spectroscopic methods. The association between nanoparticles and FPPBI is explained from both absorption and fluorescence quenching data. The distance between FPPBI and Al2O3 as well as the critical energy transfer distance has been deduced.

Self-assembly layer-by-layer fabrication using porphyrin dye anion and polycation

In this study, self-assembled alternating film using poly(diallyldimethylammonium chloride) (PDDAC) and meso-tetrakis(4-carboxyphenyl)porphyrin (MTCP) was prepared as a multilayer deposition on glass substrate. This preparation technique for dye deposition may provide new feasibilities to achieve the manufacture of ultrathin films for nanotechnology application. The deposition films were characterized by UV-vis spectrophotometer and Atomic Force Microscopy (AFM) analysis. The results of UV-vis spectra showed that the absorbance characteristic of the multilayer films linearly increased with an increased number of PDDAC and MTCP bilayers. AFM analysis showed the film surface was relatively uniform and the progressive growth of layers was determined.

Fluorescence Quenching of Meso-Tetrakis(p-Sulfonatophenyl)Porphyrin (TSPP) by certain Organic Dyes

The fluorescence quenching of meso-tetrakis (p-sulfonatophenyl) porphyrin (TSPP) by certain anthraquinone and azo dyes has been investigated using steady state fluorescence technique. The dyes used were Uniblue-A, Acid blue 129, Alizarin, Alizarin red S, Erichrome Black T, Tartrazine, Methyl orange, Methyl red, Acid orange 63 and Congo red. The quenching was found to obey Stern-Volmer equation and the corresponding Stern-Volmer plots were linear. The quenching rate constant (k q ) is in the order of 0.19–6.08×1012 M− 1s− 1. This study reveals effective quenching of TSPP by organic dyes.

Studies on the interaction of interface between morin and TiO2

For the first time, the interaction between morin and TiO(2) nanoparticles was investigated by UV-vis absorption, UV-vis diffuse reflectance spectrum, FT-IR, fluorescence, and three-dimensional fluorescence spectra techniques. The results showed that chemical bonds had formed between the surface atoms of TiO(2) nanoparticles and morin molecules. The fluorescence intensity of TiO(2)-morin nanocomposites was much higher than that of morin particles. In addition, the effect of TiO(2) concentrations on the fluorescence intensity of morin was also investigated.

Cyanobacterial chlorophyll as a sensitizer for colloidal TiO2

Chlorophyll has been extracted from cyanobacteria. The adsorption of chlorophyll on the surface of colloidal TiO(2) through electrostatic interaction was observed. The apparent association constant (K(app)) of chlorophyll-TiO(2) obtained from absorption spectra is 3.78x10(4)M(-1). The K(app) value of chlorophyll-TiO(2) as determined from fluorescence spectra is 1.81x10(4)M(-1), which matches well with that determined from the absorption spectra changes. These data indicate that there is an interaction between chlorophyll and colloidal TiO(2) nanoparticle surface. The dynamics of photoinduced electron transfer from chlorophyll to the conduction band of colloidal TiO(2) nanoparticle has been observed and the mechanism of electron transfer has been confirmed by the calculation of free energy change (DeltaG(et)) by applying Rehm-Weller equation as well as energy level diagram. Lifetime measurements gave the rate constant (k(et)) for electron injection from the excited state chlorophyll into the conduction band of TiO(2) is 4.2x10(8)s(-1).

Interaction between certain porphyrins and CdS colloids: a steady state and time resolved fluorescence quenching study

The interaction between porphyrins namely, meso-tetrakis (4-methoxyphenyl)porphyrin (TMeOPP), protoporphyrin IX (PPIX) and Zinc(II) meso-tetraphenylporphyrin (ZnTPP) with colloidal CdS has been studied by using steady state and time resolved fluorescence quenching measurements. The porphyrins adsorbed on the surface of colloidal CdS due to electrostatic interaction. This adsorption leads to changes in the absorption spectra related to the complex formation. The apparent association constant (Kapp) was in the order of 4.34-5.58 x 10(5) M(-1) from the effect of colloidal CdS on the absorption spectra and 0.64-1.6 x 10(5) M(-1) from fluorescence quenching data. Quenching is attributable mainly to static mechanism through ground state complex formation as confirmed by lifetime measurements.