Radiolysis and photolysis studies on active transient species of berberine.

In this paper, the photochemical and photobiological characters of the active radicals of berberine (BBR) was investigated for finding an efficient and safe photosensitizer with highly active transient products using in Photodynamic therapy (PDT) study. The active species of BBR was generated and identified by using pulse radiolysis method. In neutral aqueous solution, BBR react with hydrated electron and hydroxyl radical, forming the radical anion and neutral radical of BBR, and the related reaction rates were determined as 3.5×10(10) and 6.7×10(9) M(-1) s(-1), respectively. Further, the capability of BBR to photosensitize DNA cleavage was testified by laser flash photolysis (LFP) method, the results demonstrated that BBR neutral radical could react with guanine mononucleotide (K=1.9×10(9) M(-1) s(-1)) via electron transfer to give the guanine neutral radical. Additionally BBR selective cleavage single and double strand DNA at guanine moiety was observed. Finally, combining with the thermodynamic calculation, the possible photodamage mechanism of dGMP and DNA induced by BBR was clarified.

Interaction mechanism between berberine and the enzyme lysozyme.

In the present paper, the interaction between model protein lysozyme (Lys) and antitumorigenic berberine (BBR) was investigated by spectroscopic methods, for finding an efficient and safe photosensitizer with highly active transient products using in photodynamic therapy study. The fluorescence data shows that the binding of BBR could change the environment of the tryptophan (Trp) residues of Lys, and form a new complex. Static quenching is the main fluorescence quenching mechanism between Lys and BBR, and there is one binding site in Lys for BBR and the type of binding force between them was determined to be hydrophobic interaction. Furthermore, the possible interaction mechanism between BBR and Lys under the photoexcitation was studied by laser flash photolysis method, the results demonstrated that BBR neutral radicals (BBR(-H)) react with Trp (K=3.4×10(9)M(-1)s(-1)) via electron transfer to give the radical cation (Trp/NH(+)) and neutral radical of Trp (TrpN). Additionally BBR selectively oxidize the Trp residues of Lys was also observed by comparing the transient absorption spectra of their reaction products. Through thermodynamic calculation, the reaction mechanisms between (3)BBR and Trp or Lys were determined to be electron transfer process.

Characterization of the transient species generated by the photoionization of Berberine: a laser flash photolysis study.

Using 266 nm laser flash photolysis it has been demonstrated that Berberine (BBR) in aqueous solution is ionized via a mono-photonic process giving a hydrated electron, anion radical that formed by hydrated electron react with steady state of BBR, and neutral radical that formed from rapid deprotonation of the radical cation of BBR. The quantum yield of photoionization is determined to be 0.03 at room temperature with KI solution used as a reference. Furthermore utilizing pH changing method and the SO(4.)(-) radical oxidation method, the assignment of radical cation of BBR was further confirmed, the pK(a) value of it was calculated, and the related set up rate constant was also determined.

Nanotoxicity of TiO(2) nanoparticles to erythrocyte in vitro.

Titanium dioxide (TiO(2)) has been considered as non-toxic mineral particles widely used in the fields like cosmetics, food and drug. When the scale come to nanometer, TiO(2) nanoparticles (nano-TiO(2)) exhibits multiple specific characteristics coupled with unknown risks on health. The purpose of this study was to systematically research the influence of nano-TiO(2) on erythrocyte. The results indicated that the erythrocytes treated with nano-TiO(2) underwent abnormal sedimentation, hemagglutination and dose dependent hemolysis, totally differing from those treated with micro-TiO(2). The ghost cells were firstly investigated by using ultra-thin cell section in the case under nano-TiO(2). The mechanism of such adverse effects is (1) the attachment around erythrocyte change the surface native properties and ultimately lead to hemoagglutination; (2) the content leak to the outside of erythrocyte through the breakage induced by both the nano-TiO(2) trans-membrane and the oxidative stress under nano-TiO(2). Our findings imply that nano-TiO(2) may have potential toxicity to human being health.

[Synthesis and screening of polyethylenimine as a carrier for gene transfer into cultured human tumor cells].

BACKGROUND & OBJECTIVE: Choosing suitable gene carrier is very important in gene therapy. Recently, polyethylenimine (PEI), a new polycation compound, is particularly attractive due to its high transduction efficiency and low toxicity. This study was to synthesize a series of PEI nanogels of different particle diameters by photochemistry, investigate the relation between the transfection efficiency and particle diameter, and screen ideal gene carrier. METHODS: PEI nanogels were synthesized by photochemistry. The particle diameter was detected by photo correlation spectroscopy (PCS). The spherical morphology of the nanogels was characterized by scanning electron microscopy (SEM), and confirmed by atomic force microscopy (AFM). Using PEI/DNA complex as a plasmid vector, the enhanced green fluorescence protein (EGFP) gene was transferred into Bel7402 and A549 cells. Gene expression was quantitatively evaluated by fluorescent microscopy and flow cytometry (FCM). RESULTS: The diameter of synthesized PEI nanogels was in the range of 80-200 nm, and most of them were globular. The delivery rate reached the maximum when using 4 microg PEI (86.9 nm) to transfer 2 microg EGFP: the delivery rates were (32.75+/-1.01)% for Bel7402 cells and (29.81+/-1.84)% for A549 cells when detected by fluorescent microscopy, and were (32.40+/-1.41)% for Bel7402 cells and (30.00+/-1.86)% for A549 cell when detected by FCM. There was no significant difference between PEI and LipofectamineTM 2000 in the transfection efficiency (P > 0.05). CONCLUSIONS: PEI nanogels synthesized by photochemistry are effective nonviral vectors for gene delivery into human tumor cells in vitro. The transfection efficiency of 86.9 nm PEI is the highest.

Size-dependent properties of M-PEIs nanogels for gene delivery in cancer cells.

Polyethyleneimine nanogels (named as M-PEIs) with different sizes were prepared by photo-Fenton reaction in aqueous solution from which samples of 38, 75, 87, 121, 132 and 167nm were selected for in vitro transfection. The homogeneous structure and the same component made it possible to study the size effect of M-PEIs nanogels on gene transfection efficiency when loading the same quantity of plasmid DNA (pLEGFP-C1) into A549, Bel7402, BGC-823 and Hela cells. M-PEIs and its DNA complexes were characterized by photo correlation spectroscopy and atomic force microscopy. The protein expression was observed by flow cytometry and fluorescence microscopy. All of the DNA complexes had no obvious cytotoxicity and the surface charges were positive charged at the optimum weight ratio. Therefore, the expressed protein was affected by the size of M-PEIs when the same quantity of DNA was used to transfect cells. In addition, the samples of 75 and 87nm yielded the highest transfection efficiency about 30% in all of the four cell lines which were also cell line independent.

[Laser photolysis study on photochemical reactions in mixed solutions of [bmim][PF6] and acetonitrile].

Laser flash photolysis study was carried out for the first time in the binary mixture of room-temperature ionic liquid (RTIL) and traditional organic solvent. Photochemical properties of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6] and its binary mixed solutions with MeCN were investigated by laser photolysis technique at an excitation wavelength of 355 nm, using anthraquinone (AQ) as a probe molecule. It was indicated that [bmim] [PF6] itself participates in the reaction with 3AQ*. Moreover, along with the change in the ratio of RTIL to organic solvent, the decay reaction rate constant of 3AQ* changes regularly and a critical point was observed at chiRTIL = 0.06. Before the critical point, the decay rate constant increases rapidly with increasing chiRTIL; however, it decreases obviously with increasing chiRTIL after the critical point. The kinetic data are given, and the possible reaction mechanisms in mixed solutions are also speculated.

[Spectral analysis of transient species of quinoline degradation].

Quinoline's degradation was studied by pulse radiolysis. It was found that hydrated electron, hydrogen radical, hydroxyl radical and SO4*- can react with quinoline. The absorption spectra of the transient species of quinoline were obtained, and related constants were determined, but it was found that the species of Br2*- and N3*- can't react with quinoline. The results give us some advices for studing the degradation of quinoline.

[Studies of benzoic acid and its methyl substitutes by using laser flash photolysis].

In the present paper the photo-ionization and properties of excited state of benzoic acid and its methyl substitutes were studied using 248 nm laser flash photolysis. The quantum yields of hydrated electrons produced from photo-ionization, the lifetime of excited triplet, and the self quenching rate constants were also determined. It is shown that there isn't significant effect of different position of methyl residue at benzene ring on its excited triplet. The resonant excitation of triplet of benzoic acid was explored by the use of two-steps laser flash photolysis. The possible upper excited state and radical involved in the processes were guessed.

[Mechanism and kinetics studies on the degradation of acid orange 7].

The reactions of *OH and e(aq)-, with AO7 in aqueous solutions were studied by nano-second pulse radiolysis techniques. The transient absorption spectra were attributed and the second order reaction rate constants were determined by following the buildup kinetics of the transient absorptions. In combination with the analysis of the UV-Vis absorption changes of AO7 after gamma-radiolysis, the underlying reaction mechanisms were elucidated.