Design, Preparation And Characterization Of Boronic Acid Regulated P H-responsive Polysaccharic Nanocarriers For Drug Delivery

Stimuli-responsive drug delivery systems(DDSs) are developed for efficiently and specifically delivering and releasing drug in lesion site with improved bioavalability and less side effects. Recently, boronic acid and its derivatives were found to be able to form boronate ester bond with vicinal diols in alkaline condition, which was cleaved in acidic medium, thus it was explored for developing p H-responsive DDSs. In this study, DDSs based on boronic acid were designed and prepared, for target delivery and selective release of antineoplastic drugs. The main contents are as follows:(1) Preparation and characterization of dual drug loaded micellesDextran(Dex), boronic derivative of methotrexate(MTX-PBA), and doxorubicin(DOX) species were initially mixed in the organic solvent and subsequently dialyzed against water to form dual drug-loaded micelles via one-pot strategy. The results showed the micelle yield of one-pot strategy were 78.2%, as compared with traditional method, the micelle yield were high and increased about 30%. In addition, the drug encapsulation efficiency of both two drugs was also improved. TEM observation demonstrated that DDMMs were of spherical shape, and the average size was about 65 nm. Both drugs showed rapid release rate at acid mediums, the accumulated release rates of MTX-PBA and DOX in p H 5.0 buffer solutions within 24 h were about 1.75 and 1.56 times, respectively, compared with the accumulated release rates in p H 7.4 buffer solutions. In vitro cytotoxicity study illustrated the half maximal inhibitory concentration(IC50) values of MTX against He La cells were reduced form 4.14 mg/L to 0.40 mg/L, and DOX were reduced form 0.46 mg/L to 0.16 mg/L, showing synergistic efficacy against cancer cells.(2) Preparation and characterization of KGP nanoparticlesThree KGPs with different degree of substitution(DS) of gossypol(GP), i.e., 4.20%(KGP1), 11.43%(KGP2) and 14.40%(KGP3), were prepared by altering reaction conditions, respectively. KGPs could self-assemble into nanoparticles in aqueous solution and the average sizes of them were 320.2 nm, 221.6 nm and 141.2 nm, respectively. Here, we chose KGP3 as drug carriers, as it has the smallest size in aqueous solution. In vitro drug release illustrated that KGP3 behaved p H responsive drug release and the accumulated release rate of GP in p H 5.0 within 12 h was about 2.8 times of that in p H 7.4 buffer solution. In additon, the IC50 value of the KGP3 against PC-3 cancer cells was lower than that of COS-7 normal cells, showing favorable cancer cell selectivity.(3) Preparation and characterization of DGEA-KGP nanoparticlesFluoresceinamine labeled K5 polysaccharide was first prepared and then targeting peptide of DGEA was modified to obtain derivatives. Fluorescence microscope observation and flow cytometry analyzed the cellular uptake of K5 polysaccharide before or after modified by DGEA. In addition, DGEA modified KGP conjugates(DGEA-KGP) was also prepared to further achieve target delivery effects of GP. In vitro cytotoxicity study showed that DGEA-KGP inhibited more cell viability compared with KGP or GP, behaving target and enhanced inhibitory effects to PC-3 cancer cells.In summary, boronic acid regulated p H-responsive polysaccharic nanocarriers behaved target delivery and selective release of antineoplastic drugs, which have a wide range of applications in drug delivery.