| Photodynamic therapy(PDT) as a novel alternative therapy modalityhas been aroused extensive attention in recent years. It is based on the combined interaction of photosensitizer, oxygen and light and has many advantages such as effective, cooperativity, not easily to produce drug resistance. The photosensitizer is the crucial element in PDT. However, the photosensitizers used in clinic still have some shortcomings including low cell uptake, poor targeting and strong dark toxicity, retarded phototoxicity result from slow metabolism, etc. A series of novel porphyrin derivates were designed and synthesized and their photo activities were evaluated in this thesis. The goal of the work is to reveal structure-activity relationship of this kind of photosensitizers and to find high efficiency and low toxicity drug candidates for PDT. The paper comprises two parts:PART1:Synthesis and Photodynamic Antibacterial Activities Evaluation of Tetraphenylporphyrin Derivates.Bacterial infections, especially today with the emergence of the multidrug-resistant bacteria due to the overuse of antibiotics, are becoming a serious problem. It is urgent to discover new drugs or novel alternative infection therapies modalities. Photodynamic antimicrobial chemotherapy (PACT), as one of such alternative chemical therapeutic modalities, has received great attention in recent years. And it has not discovered drug-resistance to PACT up to now. The fundamental process of PACT is based upon the energy transfer from light to oxygen to produce reactive oxygen species that are lethal to microbial pathogens. Porphyrin, with the absorption wavelength matching the transparence windows of biotissue, favorable spectral properties and high singlet oxygen yields, ubiquitous in nature, good biocompatibility and clear metabolism path, is an ideal photosensitizer candidate in photodynamic therapies. It has been demonstrated that porphyrins bearing cationic groups are able to induce the photoinactivation of Gram-positive and Gram-negative bacteria and are usually more efficient than neutral and negative charged analogues to bacteria. However the intrinsic characteristics of the unnatural cationic groups don’t endow them good biocompatibility, easily produce toxic side effects in vivo and the amount of them uptake by bacteria is limited. The three basic amino acids including L-lysine, L-arginine and L-histidine are biologically important and possess great value for living systems; In addition, they bear cationic charges at physiological pH values. So the conjugation of porphyrins with basic amino acids could supply of both essential natural amino acids and the positive charges, endowing the ensemble special good biocompatibility and high affinity to strain cells, which can improve its uptake amount and the antibacterial activity.In this paper, the novel cationic porphyrins were constructed by condensation of amino phenyl porphyrin with natural basic amino acids, L-lysine, L-arginine and L-histidine.56compounds were synthesized and38of them were novel compounds. Five synthesis routes were accomplished in this part and24target compounds were synthesized. The structure of the compounds was confirmed by’HNMR and MS. The melt point, UV spectrum, photostability, singlet oxygen quantum yield, octanol-water partition coefficient and thermoanalysis were tested. The target compounds show the characteristic porphyrin absorption comprising a Soret band at420nm or so and four Q-bands at500-670nm or so. The wavelength in the maximum absorbance has slightly blue shift with the rise of the substitution number. Photobleaching experiment shows that the corresponding absorption spectra and the related optical density of the porphyrin conjugates changed a little after irradiation, which indicates that these basic amino acid porphyrin conjugates have enough high photostability. The measurement of quantum yields of1O2showed that they have a higher efficiency to generate singlet oxygen under the same experimental conditions. Compound4i, with four lysine moieties, showed highest ability to produce singlet oxygen (Φ△=0.95). And the water-solubility were improved when the amino acid groups were introduced. The experiment of thermoanalysis suggested that those compounds were stable before200℃.The photodynamic antibacterial activities were evaluated including uptake, MIC and MBC, dose-dependent photoinactivation effects and confocal laser scanning microscopy images. Their PACT efficacy against MRSA, E. coli and P. aeruginosa was improved along with the numbers of lysine. Compounds4c,4e and4g with porphyrin bearing two lysine moieties showed good effects, which eradicated E. coli at rates of3.0-log10reduction in the survival fraction, MRSA<6.0-log10, P. aeruginosa2.5-log10reduction at a concentration of10μM. The compound4i, with porphyrin bearing four lysine moieties, showed the highest photodynamic antibacterial activity among these kinds of compounds, which eradicated4.0-log10for MRSA,3.0-log10for P.aeruginosa and<6.0-log10reduction in the survival fraction for E. coli.Those compounds deserve further study.PART2:Photodynamic Antibacterial Activities Evaluation and Structure-Activity Relationship Study of Porphyrin Derivates.On the basis of previous work in our laboratory, we constitute to investigate the synthesis and photodynamic antibacterial activities of porphyrin derivates and perfect their SAR in terms of the results.21compounds were evaluated using MTT method.The result showed that the activity was concentration-dependant at rang of1.25-20μM. The inhibition ratio was larger than80%at5μM for the compounds4a and4j and the compounds had low dark toxicity (<30%). Compounds4f,4b,4c and4e showed higher inhibition ratio to Hela (87.91%,79.31%,81.64%,85.06%at2.5μM and IC50:<0.05μM,1.24μM,0.90μM,1.85μM respectively). The preliminary structure-activity relationship showed that the amino group in the phenyl can improve the antitumor activity. The introduction of one or two lysine also improved the antitumor activity while multi-substitution made the activity lower. |
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