Responsive Photonic Crystal Beads For Metal Ion Detection And Research On Controlled Release Of Drugs

Responsive photonic crystals are widely used in the fields of analysis and detection,display anti-counterfeiting,and fluorescence enhancement due to their unique optical properties.However,the structural color of photonic crystals is angle-dependent,and the reaction time in analytical detection is long,and these shortcomings limit its practical application.Inverse opal photonic crystal beads have an interconnected three-dimensional macroporous structure,which has a larger surface area than flat films,so it has a more sensitive and faster response;and its spherical symmetrical structu re endows it with an angle-independent structural color,which is not easy to cause disturbance to the observer.All these properties make inverse opal photonic crystal beads a promising sensor material.Photonic crystal beads are usually synthesized using microfluidic chips,which can be prepared in the shearing of two phases.And inverse opal photonic crystal beads are prepared by combining photonic crystal beads with functional hydrogels.Various functional groups can be modified on it to respond to different substances.In this paper,through the design of hydrogel components,inverse opal photonic crystal beads for the visual detection of UO₂²⁺,Hg²⁺and controlled drug release were prepared,which utilize its characteristics of miniaturization,simple operation and stable signal.The specific research contents are as follows:（1）A series of photonic crystal beads were prepared using microfluidic technology.By controlling the flow rate of dispersed phase and mobile phase,photonic crystal beads with uniform size were obtained.And by controlling the diameter of template silica nanoparticles,the whole visible spectrum of photonic crystal beads can be prepared.The UO₂²⁺responsive inverse opal photonic crystal beads were prepared by template replication method,which contained cyano and amide groups.The cyano and amide groups were activated to amidoxime and carboxyl groups by a two-step activation method,respectively.The reflection peaks of the activated inverse opal photonic crystal beads are red-shifted.When the solution of UO₂²⁺were added,the coordination of UO₂²⁺with amidoxime and carboxyl groups leads to the shrinkage of the hydrogel skeleton.So the reflection wavelength shifts blue,and the color of the inverse opal photonic crystal beads changes accordingly.Changes in UO₂²⁺concentration resulted in different degrees of shrinkage of the hydrogels,which were detected by structural color changes and measurement of reflected wavelengths.Compared with large-sized planar photonic crystal films,inverse opal photonic crystal beads have a larger surface area,which endows the sensor with more binding sites and faster response speed.The lower limit is 1 n M,and there is good linearity and color change in the low concentration range of 1 n M to 0.1μM.Besides,the prepared inverse opal photonic crystal bead sensor has good reusability and specificity,and realizes UO₂²⁺detection in actual water samples.（2）An inverse opal photonic crystal bead with Hg²⁺responsiveness was prepared using a disulfide cross-linking agent to form a hydrogel network.When dithiothreitol breaks the disulfide bond in the hydrogel crosslinker N,N’-methylenebis（acryloyl）cystamine（BAC）,the hydrogel network swells,and the different Relationship between disulfide bond content and change in reflected wavelength of inverse opal photonic crystal beads.The sulfhydryl group generated after the cleavage of the disulfide bond,as a nucleophile,has a stron g binding force with Hg²⁺and can form a-S-Hg-S-bond in the hydrogel network to drive the inverse opal photonic crystal bead network to shrink,causing The blue-shift of the reflected wavelength enables the visual detection of Hg²⁺.After comprehensive consideration,0.74 wt%BAC content,which is the most favorable for visual detection,was selected as the condition of subsequent experiments.The lowest detection concentration was 0.05μM,and in the detection range of 0.05μM to 10μM,the logarithm of the concentration and the reflection peak shift showed a good linear relationship.Besides,the prepared disulfide bond inverse opal photonic crystal beads have good specificity and reusability,and show good results in the detection of actual water samples.（3）Inverse opal photonic crystal beads containing disulfide crosslinkers and acrylic monomers were prepared to explore their application in drug release.The acrylic monomer is selected to participate in the polymerization,and the drug is adsorbed and loaded through the electrostatic force between the carboxyl group and the amino group on the drug doxorubicin hydrochloride.In 10 m M PBS buffer at p H=7.4,the drug loading rate reached 71%within 24 h,and the drug loading amount reached 4.27μg/mg.According to the characteristics of glutathione overexpression and strong acidity in the surrounding physiological environment of tumor cells,the drug release simulation was carried out in vitro.The disulfide bond in the hydrogel is reduced by glutathione,so that the cross-linked network is destroyed,and the acidic condition weakens the electrostatic force between doxorubicin hydrochloride and the carboxyl group,so that the drug is released.The maximum drug release rate was 62%in PBS buffer containing 10 m M GSH,p H=5.4.The biocompatibility of the blank carrier was tested,the good biocompatibility of the drug carrier was proved,and the cytotoxicity of the drug carrier to cancer cells was verified.The kinetics of the drug release process was simulated,and it was found by fitting that the drug release conformed to the Korsmeyer-Peppas model,and the release mechanism conformed to the Fick diffusion mechanism.