| Perylene diimde is a kind of excellent fluorescent chromophore with good light and thermal properties. It has special ultraviolet absorption and corresponding fluorescence emission band (600-630 nm) closing to the near-infrared light band (650-900 nm). Perylene diimde cored star polymers can inherit its fluorescence properties and improve its solubilities. Star polymer is a member of dendritic polymers. Compared with the linear polymers, star polymers have special topology advantages. They have the internal cavity structure and abundant functional groups outside. Because of these advantages, they have broad applications in biomedical fields such as drug delivery. Star polymers are easier to be produced, when compared with dendrimers. So we can expect star polymers to realize mass production conveniently and costlessly. These advantages make star polymer suitable for synthesis of functional polymers. Stimuli-response polymers are functional polymers, which can response to the external environmental stimuli, such as pH, temperature, light, electrolyte molecules and voltage. Ionic polymers belong to stimuli-response polymers. They can response to electrolytes or pH value. Specially, the cationic polymers are also used as gene vectors. In this paper we introduced many perylene imide cored ionic polymers with star shapes. The polymers are prepared by atom transfer radical polymerization (ATRP) and polymer modifications. Before the production of polymers, we synthesized two kinds of perylene derivatives as ATRP initiators first. In the process, we used hydroxyl protection strategy and esterification reactions. The main content of this paper is involving in the applications in pH probes and gene vectors using the star polymers. The research results of this paper can be divided into the following several aspects:1. By the decoration on’bay’ position, two ATRP initiators was synthesized from perylene diimide derivatives. The raw material named 4C1-PDI has been produced previously in our laboratory. Through substitution reaction,4C1-PDI was hydroxylated and the obtained chemical product was named as 4OH-PDI. Then 4OH-PDI was reacted with 2-bromoisobutyryl bromide and the the four-arm initiator called 4Br-PDI with four bromine atoms was obtained. Using the synthetic method of dendrimers, we firstly synthesized 80H-PDI which was derived from 4OH-PDI. After reacted with 2-bromoisobutyryl bromide,8OH-PDI was turned into the eight-arm initiator (8Br-PDI).2. In our research, we used another eight-arm initiator (initiator 1), which has been synthesized in our laboratory. Using the three kinds of initiators above, we synthesized a variety of fluorescent star polymers through ATRP polymerization. After modifications, eventually we got the fluorescence star polyelectrolytes, including two kinds of anionic polymers and six kinds of cationic polymers. We use nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) curves for the characterization of the polymers respectively.3. For the first time, we use fluorescent star polymers as the materials for preparing pH fluorescent probes. Perylene diimide-polyacrylic acid (PDI-PAA) and perylene diimide-poly(2-aminoethyl methacrylate) (PDI-PAEMA) are the representatives of fluorescent star anionic and cationic polymers respectively. Our research showed that both kinds of polymers formed unimolecular micelles in aqueous solutions, and pH adjustment can cause the changes of micelle sizes. These conclusions were based on the data derived from small angle X-ray scattering (SAXS) and dynamic light scattering (DLS) characterizations. The following research indicated that the changes of micelle sizes could lead to the corresponding changes of solution fluorescence. The changes of pH values can cause the irreversible changes of fluorescence intensities. Through our research, we concluded the internal reasons of the fluorescence changes are the fluorescence quenching effect induced by water molecules and the volume phase transition of the unimolecular micelles. This principle can also be applied for other fluorescence star polymers.4. Two kinds of four-arm fluorescent star cationic polymers, i.e. PDI-PAEMA and perylene diimide-poly(2-(dimethylamino)ethyl methacrylate) (PDI-PDMAEMA), were studied for gene delivery and cell imaging. Their gene transfection efficiencies were made a comparison. Both of the polymers were cored by perylene diimide. Their side groups were primary amines or tertiary amines respectively. They had the same number of repeat units and similar optical properties. Agarose gel electrophoresis experiment showed that under the condition of a relatively low ratio of nitrogen and phosphorus (N/P> 8:1), the polymers can form stable complexes with the negative charged DNA. Further cell experiments showed that these kinds of complexes can successfully enter cells, and had good effect on fluorescence imaging. When compared with polyethyleneimine (PEI), both of the two polymers had obvious advantages on the toxicities and transfection efficiencies. Specially, PDI-PDMAEMA has higher gene transfection efficiency than PDI-PAEMA.5. In order to find a better method to prepare gene vectors with high transfection efficiency, we synthesized four-arm or eight-arm fluorescent star poly(glycidyl methacrylate)s (PDI-PGMAs). After the ring opening reactions with ethylenediamine (EDA) or N’-(3-ammonia propyl)-N, N-dimethyl-1,3-propylene amide (DMDPA) under mild conditions, cationic polymers poly(glycerol methacrylate)s (PGOHMAs), i.e. SP1, SP2 and SP3, were produced. Their aqueous solutions have good fluorescence properties, and all of the fluorescence quantum yields ((?)f) were higher than 0.1. In agarose electrophoresis experiments, when the nitrogen and phosphorus ratio was higher than 2:1, SP2 can form stable compounds with DNA. Cell toxicity experiments showed that all of these PGOHMAs have good biocompatibility. In these three kinds of polymers, SP2 had the highest gene transfection efficiency, which would be an ideal fluorescent polymer as a kind of gene vector. |
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