Determination of doxorubicin amount conjugated to mPEG-b-PCL copolymer via pH sensitive hydrazone bond

Objective: The aim of this study was to find the efficient medium to bind an anticancer drug, Doxorubicin (DOX), to a synthesized polymer, methoxy poly(ethylene glycol)-block-polycaprolactone (mPEG-b-PCL) via pH sensitive hydrazone bonds and to determine the amount of conjugated drug. Methods: DOX conjugation was carried out in two different media [dimethyl sulfoxide (DMSO) and methanol-trifluoroacetic acid (MeOH-TFA)]. The amount of conjugated drug was determined with two different methods. One method was applied the dissolution of the conjugate in chloroform: methanol (Ch: MeOH, 1: 1 v/v) solution without considering pH responsiveness, and the other method was after breaking pH sensitive hydrazone bonds in acidic medium [using three different media as 0.1 M hydrochloric acid (HCl), concentrated HCl (12 M HCl) and concentrated sulfuric acid (18.3 M H2SO4)]. Results: The highest conjugation efficiency was obtained when the conjugation was achieved in MeOH-TFA solution, and for the polymer-drug conjugates after the treatment with concentrated sulfuric acid. recognized by immune system rapidly (12). On the other hand, PEG is hydrophilic and can escape from the immune system. Scientists prepared or used copolymers or tri-block-polymers of PEG and PCL and prepared either nanoparticles or micelles as drug delivery vehicles and evaluated in vitro and in vivo properties (13). Gong et al studied affinity of PEG-PCL-PEG micelles (14). Hu et al prepared micelles and polymersomes from PCL-PEG-PCL polymers to be used as drug carriers (15). Cytotoxic properties of Doxorubicin loaded PEG-PCL micelles prepared with functionalized PEGs were evaluated by Chen et al. and promising results were reported (16). An accurate determination of drug conjugation is important since higher dose given to a patient may create some unwanted symptoms like cardiomyopathy. In this study, methoxy konjugasyonu Conclusion: It was concluded that, MeOH-TFA method was a good method for conjugation of DOX to M) method was better other present in literature for determination of the amount of DOX linked to the polymer via