Preparation And Properties Of Magnetic Fluorescent Polymer Microspheres

Functional microspheres are becoming more and more important in biomedical applications.Magnetic fluorescent microspheres with properties of superparamagnetism and fluorescence can realize the functions of screening,isolating,and ensuring the accuracy and efficiency of testing at the same time,which make it precede the traditional single?function microspheres.At present,many synthesis methods such as LBL(Layer-By-Layer),polymerization method,embedding method,swelling method and so on have been used to prepare magnetic fluorescent microspheres.But there are still some drawbacks,such as the cumbersome process of preparation,the instability and low loading capacity of functional particles.According to the present situation,a new synthetic strategy was proposed in this study.First,hyper-crosslinked microporous microspheres(HCMPs)with appropriate pore size micropores were synthesized.Then ferriferous oxide and CdSe/ZnS quantum dots,as the magnetic and fluorescent sources,were loaded into the microspheres through in?situ co?precipitation method and swelling method,respectively.Thus,the dual functionalizations of magnetism and fluorescence of the HCMPs were realized.Firstly,monodisperse micron-grade polystyrene?divinylbenzene?acrylic(PS?DVB?AA)microspheres were synthesized through reflux precipitation polymerization with styrene(St)and acrylic acid(AA)as the monomer,divinylbenzene(DVB)as cross?linking agent,2,2’-Azobis(2-methylpropionitrile)as the initiator,acetonitrile and methylbenzene as the reaction medium.The effects of content of monomer,initiator and crosslinking agent on particle size and its distribution and the effect of AA content on Zeta potential value of microspheres were studied.The monodisperse crosslinked carboxyl?functionalized polystyrene particles with an average particle size of 2.2 μm were synthesized under the optimized conditions,and the problem of being difficult to homogeneous crosslinking in the preparation process of crosslinked microspheres was solved perfectly.Infrared(FT?IR)demonstrates that crosslinked microspheres are copolymerized with St,DVB and AA,transmission electron microscopy(TEM)shows that crosslinked PS?DVB?AA microspheres have good spherical shape and monodispersity,and the microsphere surface potential increase gradually with increasing AA concentration.Secondly,hyper-crosslinked microporous microspheres(HCMPs)of high surface area,rich micropores and mesoporous were synthesized via Friedel?Craft alkylation’s reaction with crosslinked PS?DVB?AA microspheres as precursor and formaldehyde dimethyl acetal(FDA)as external crosslinker.It turns out that the content of DVB have great influence on microspheres’ surface area and pore structure.The surface area and pore volume of HCMPs increase with DVB content increasing.When the content of DVB reaches 80%,the HCMPs’ BET surface area can be as high as 740.5 m2·g-1.The result of nitrogen adsorption?desorption isotherm,pore size distribution curve and T-plot curve indicate that HCMPs are filled with mesoporous and macroporous when DVB content is 20% and 40%,HCMPs are full of microporous when DVB content is 60% and 80%,and the pore size distribution is the most uniformly when DVB content is 60%.In order to realize the magnetic and fluorescent functionalization of HCMPs,the magnetic fluorescent polymer microspheres loaded with Fe3O4 nanoparticles and CdSe/ZnS quantum dots were prepared by in-situ co-precipitation method and swelling method with HCMPs as carriers.According to experimental results,the magnetic fluorescent HCMPs show a faster magnetic response in the external magnetic field,which means HCMPs have superparamagnetism.The saturation magnetizations of the magnetic fluorescent HCMPs increase with an increase in concentration of the iron ion,and when the iron ion concentration is 1.5 mol/L,the saturation magnetizations reach the highest,as 38.6 emu/g.Fluorescence spectra and fluorescence microscopy(FM)indicates the exsistence of quantum dots in HCMPs.Under the ultraviolet light,the magnetic fluorescent HCMPs present green fluorescence and its distribution is uniform.The fluorescence intensity increases with the increase of quantum dots which indicates the increasing of loading capacity of quantum dots.This research has laid a good foundation for the further study of magnetic fluorescent HCMPs for liquid biochip.