Abstract
A new methodology for the pH-triggered degradation of polymers or for the release of drugs under visible light irradiation based on the cyclization of ortho-hydroxy-cinnamates (oHC) to coumarins is described. The key oHC structural motif can be readily incorporated into the rational design of novel photocleavable polymers via click chemistry. This main-chain moiety undergoes a fast photocleavage when irradiated with 455nm light provided that a suitable base is added. A series of polyethylene glycol-alt-ortho-hydroxy cinnamate (polyethylene glycol (PEG)n -alt-oHC)-based polymers are synthesized and the time-dependent visible-light initiated cleavage of the photoactive monomer and polymer is investigated in solution by a variety of spectroscopic and chromatographic techniques. The photo-degradation behavior of the water-soluble poly(PEG2000 -alt-oHC) is investigated within a broad pH range (pH = 2.1-11.8), demonstrating fast degradation at pH 11.8, while the stability of the polymer is greatly enhanced at pH 2.1. Moreover, the neat polymer shows long-term stability under daylight conditions, thus allowing its storage without special precautions. In addition, two water-soluble PEG-based drug-carrier molecules (mPEG2000 -oHC-benzhydrol/phenol) are synthesized and used for drug delivery studies, monitoring the process by UV-vis spectroscopy in an ON/OFF intermittent manner.
Highlights
“smart” polymers, which have gained interest from industry and academia alike
Choosing 1a as a model substrate (Table 1), we established that no formation of the coumarin product 2a is observed either upon irradiation at 455 nm without the addition of base N,Ndiisopropylethylamine (DIPEA) or in the presence of a base without irradiation
Substrates 1b–1g could be transformed to the corresponding coumarins 2b–2g upon irradiation at 455 nm (Table 1), going along with a bathochromic shift upon addition at DIPEA (Figure S10, Supporting Information)
Summary
“smart” polymers, which have gained interest from industry and academia alike. The release of drugs under visible light irradiation based on the cyclization of exposure of the material to environmenortho-hydroxy-cinnamates (oHC) to coumarins is described. The key oHC tal changes such as temperature, pH, restructural motif can be readily incorporated into the rational design of novel photocleavable polymers via click chemistry This main-chain moiety undergoes a fast photocleavage when irradiated with 455 nm light provided dox, enzyme, voltage, gas, mechanical force, and light causes alterations in the physical and chemical properties, which leads to changes in dimensions, aggregation states, that a suitable base is added. Two water-soluble PEG-based drug-carrier molecules involved, and allow the tuning of relevant parameters such as light intensity or irradiation time and wavelength. In this context, light-cleavable polymers are of special value:[3] Their ability to degrade (mPEG2000-oHC-benzhydrol/phenol) are synthesized and used for drug into smaller fragments upon irradiation delivery studies, monitoring the process by UV–vis spectroscopy in an ON/OFF intermittent manner.
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