Redox reactions and fluorescence spectroscopic behaviour of trifluoperazine at the surface of colloidal silica

doi:10.1016/j.bpc.2003.10.022

Biophysical Chemistry

Volume 109, Issue 1, 1 April 2004, Pages 113-119

https://doi.org/10.1016/j.bpc.2003.10.022 Get rights and content

Abstract

Fluorescence spectroscopic behaviour and redox reactions of trifluoperazine (TFP) were studied in aqueous solutions in the presence of silica (SiO₂) particles. The effect of surface heterogeneity on the secondary reactions of the transients was determined using optical absorption and fluorescence techniques. It appears that electrostatic interaction is the driving force for adsorption of TFP over SiO₂ particle. Contrary to the change in fluorescence intensity with time observed in an aqueous solution, fluorescence intensity of TFP did not change significantly with time over the surface of SiO₂. Fluorescence microscopic observations of spleen cells treated with TFP over SiO₂ showed that the drug got distributed in cells similar to that observed in homogeneous aqueous solution.

Introduction

Phenothiazines are good electron donors and can be photo-oxidised by near UV light. It has been reported that photo-induced charge separation in porous inorganic materials can achieve long lifetimes of photo-induced radical ions at room temperature [1]. This is because the back electron transfer rates are retarded in heterogeneous systems compared to that in the homogeneous solution.

Phenothiazine derivatives are widely used in the formulation of drugs and as photosensitizers. Therefore, phenothiazine drugs reactions with free radicals are well studied [2], [3], [4], [5]. However, serious photo-toxic reactions (mainly diseases of epidermis and dermis) as well as photo-allergic and photo-mutagenic effects can be induced in patients subjected to irradiation with sunlight while treated with pharmacologically important chemicals such as tranquilizers. Such noxious effects are correlated to the drug photochemical activity and are substantially reduced in the presence of cyclodextrins with phenothiazines [6].

It is known that adsorption of a drug or protein to a surface generally produces a change in its physicochemical properties. This may affect the biological functioning of the molecule. Thus, in biomedicinal, biotechnological applications, food processing, etc., the occurrence of interfaces is of significant importance. Owing to the above-mentioned reasons, it has become very important to study the effect of adsorption on the stability of drugs to develop new bio-compatible materials. Recently, we have studied redox reactions of trifluoperazine (TFP) in aqueous solutions [7]. In this study we have extended our work by embedding TFP onto silica surface.

There were three main aims of this study. First, redox reactions of TFP were investigated and compared with that of dissolved TFP. Second, stability of TFP was investigated over SiO₂ since it is known that phenothiazine drugs photo-degrade in the dissolved state. Third, whether the cells treated with TFP show similar uptake of the drug both when it is adsorbed and in the dissolved state.

Section snippets

Materials

TFP was obtained from Sigma and used as received. Silica (SM-30, 30 wt.%) was obtained from Aldrich. All other chemicals and reagents were HPLC, AR or GR grade. IOLAR grade (purity >99.99%) gases (N₂ or N₂O) used for bubbling the solutions were obtained from Indian Oxygen Limited. The pH was adjusted with Na₂HPO₄ to the required value. Nanopure water (conductivity 0.1 μS cm⁻¹) from a Barnstead (USA) nanopure water unit was used for making solutions. Centrifuge tubes were obtained from Nalgene

Results and discussion

TFP is known to exist in aqueous solution in different states of protonation, depending on pH of the solution. Two pK_a values for TFP are reported to be 4 and 8.1 [11]. Therefore, most of our work was carried out at pH 6.

Conclusion

The radiolytic and photolytic degradation of TFP gets inhibited when it is adsorbed over the surface of SiO₂. Also, the adsorbed TFP over the surface is able to penetrate into the cells. The work presented may have important biological implications.

Acknowledgements

The authors are thankful to Dr J.P. Mittal, Director, Chemistry and Isotope Group, for encouragement.

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View full text

Redox reactions and fluorescence spectroscopic behaviour of trifluoperazine at the surface of colloidal silica

Abstract

Introduction

Section snippets

Materials

Results and discussion

Conclusion

Acknowledgements

Boichim. Biophys. Acta

J. Coll. Int. Sci.

Anal. Chim. Acta

J. Non-Cryst. Solids

Photooxidation of alkylphenothiazines in SiMCM-48, AlMCM-48, and VCM-48 mesoporous molecular sieves

Phys. Chem. Chem. Phys.

Free radical induced one-electron oxidation of the phenothiazines, chlorpromazine and promethazine

J. Chem. Soc. Perkin Trans.

Laser photo-ionisation of phenothiazine in micellar solution (II) mechanism and light induced redox reactions with quinines

Ber. Bunsenges, Phys. Chem.

Mechanistic studies on the photooxidation of chlorpromazine in water and ethanol

Bull. Chem. Soc. Jpn.

Photoprocesses of photosensitizing drugs within cyclodextrin cavities

Chem. Soc. Rev.