| The side chains with ionic functional groups or grafted hydrophilic side chains were introduced into the main chain of water-soluble conjugated polymers(WSCPs),which greatly improved the water solubility and biocompatibility of WSCPs,and retained the good photoelectric properties,such as excellent photostability and high molar extinction coefficient,etc..Studies have shown that WSCPs with near-infrared absorption can be used in biological imaging and phototherapy with good penetrability,which is beneficial to the diagnosis and treatment of deeper biological tissues with high signal-to-noise ratio,and can avoid a certain degree of light-induced damage.WSCPs are often used in phototherapy because of their photostability,high photodynamic and photothermal conversion efficiency.In photothermal treatment,WSCPs can convert light energy into heat energy after absorbing light,and the heat generated makes the temperature of tissue rise,thereby killing the cells in the focus.WSCPs can also be used in photodynamic therapy.After the laser excitation of appropriate wave band,the electron transitions to the triplet energy level,and finally reacts with oxygen,returns to the ground state and produces singlet oxygen with strong oxidationzing ability.These singlet oxygen can produce strong cell and tissue killing ability at the location of the locus.However,the research of WSCPs in phototherapy is still in the primary stage.Due to the inherent hydrophobic characteristics of conjugated polymers,such materials still have problems such as low water solubility,photodynamic and photothermal effects to be improved,and the structureactivity relationships between the molecular structure and singlet oxygen yield,photothermal conversion efficiency are still to be further studied.Diketopyrrolopyrrole(DPP)has a broad absorption peak,a high photothermal conversion efficiency and a certain singlet oxygen generation capacity,and it is relatively easy to achieve near infrared absorption.Therefore,we designed and developed a series of new WSCPs,using fluorene derivatives as electron donors(donor,referred to as D),DPP derivatives as electron acceptors(acceptor,referred to as A)),and ethylene bond as ?-conjugate bridge,and the monomer side chain was hydrophilically modified.Two near-infrared absorption WSCPs with the main chain structure of D-?-A were obtained.The main research work is as follows:(1)The fluorene derivative monomer was obtained by introducing an ether-containing hydrophilic side chain at the 9-position of fluorene,and the thiophene groups were connected on both sides of DPP to obtain the DPP derivative monomer.The neutral conjugated polymer P1 was obtained by the ethylene bond bridging of the two,and the near-infrared absorption cationic WSCP P1' was obtained by the quaternization of P1.P1 'showed an absorption peak at 680 nm.In aqueous solution,the intensity of photoacoustic signal gradually increased with the increase of illumination power.The singlet oxygen yield of P1' was 37.3%,and the photothermal conversion efficiency was 41.7%.The results showed that P1' has the potential of photodynamic and photothermal therapy under the guidance of photoacoustic imaging.(2)In order to further improve the water solubility,a neutral water-soluble conjugated polymer P2 was obtained by linking the polyethylene glycol(PEG)segment on the sidechains of DPP derivative monomer,and then bridging with fluorene derivative monomer via ethylene bond.The water solubility ratio of P2 was much better than that of which is P1',the singlet oxygen yield of P2 is 47.8%,and the photothermal conversion efficiency is 33.1%,indicating that the introduction of PEG side chains containing heteroatom can further improve singlet oxygen yield.In vitro He La cell experiment confirmed the good photodynamic / photothermal effect of P2. |
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