Poly(methacrylic acid) (PMAA)-coated gelatin nanoparticles encapsulated with fluorescent dye rhodamine B were prepared by the coacervation method with the aim to retard the release of rhodamine B from the gelatin matrix. With sodium sulfate as coacervation reagent for gelatin, a kind of biopolymer with excellent biocompatibility, the formed gelatin nanoparticles were cross-linked by formaldehyde followed by the polymerization of methacrylic acid coating. The fluorescent poly(methacrylic acid) coated gelatin (FPMAAG) nanoparticles had a uniform spherical shape and a size distribution of60±5 nm. Infrared spectral analysis confirmed the formation of PMAA coating on the gelatin nanoparticles. Based on UV-Vis spectra, the loading efficiency of rhodamine B for the FPMAAG nanoparticles was 0.26 μg per mg nanoparticles. The encapsulated rhodamine B could sustain for two weeks. Favorable fluorescence property and fluorescence imaging of cells confirmed that the FPMAAG nanoparticles have promising biochemical, bioanalytical, and biomedical applications.

No abstract

Poly(styrene-acrylamide-acrylic acid) copolymer fluorescent microspheres (PSAAFMs) with improved surface hydrophilicity were synthesized through an improved soap-free emulsion copolymerization method, in which the proportion of acrylamide on the surface of the microspheres was increased. Azidocarbonyl groups, which can be rapidly coupled with proteins under mild conditions, were introduced onto the PSAAFMs using an azido reaction. The PSAAFMs were characterized using a fluorescence microscope, an ultraviolet/visible spectrometer, a Fourier transforms infrared spectrometer, a transmission electron microscope (TEM), a size analyzer, and a fluorescence spectrophotometer. Furthermore, covalent linking through the azidocarbonyl groups and physical nonspecific attachments of bovine serum albumin (BSA), trypsin, and human chorionic gonadotropin (HCG) onto the surface of the microspheres were also determined to evaluate the influence of improved surface hydrophilicity on nonspecific protein adsorption. Results from the TEM and size analyzer showed that the PSAAFMs maintained spherical shapes with an average diameter of 2.5 ± 0.22 µm. Fluorescence measurement indicated that the maximum emission wavelength underwent a slight blue shift from 514 to 512 nm. Environmental factors, such as pH value, imposed certain effects on fluorescence intensities. The linear relationship between fluorescence intensity and microspheres' concentration, which ranged from 1 × 10−3 to 10 × 10−3 g L−1, suggest their quantitative application. The significant decrease in the physical nonspecific adsorption of BSA, trypsin, and HCG in comparison with the microspheres without improved hydrophilicity suggest the increased amount of acrylamide on the surface of the microspheres. The protein covalent immobilization experiments revealed significant increases in BSA and HCG immobilization in comparison with the nonspecific physical attachment. The combination of high hydrophilicity and electrostatic repulsion could severely inhibit nonspecific protein attachment onto the surface of the microspheres.

A novel two‐step modified seeded polymerization method for the preparation of AFDFMs with a core/shell structure is developed. Their morphology is characterized by means of TEM and SEM, further characteristics are studied using FT‐IR, fluorescence microscopy, laser confocal fluorescence microscopy, and fluorescence spectroscopy. TEM and SEM images provide clear proof of a core/shell structure. Fluorescence spectroscopy shows that AFDFMs exhibit tunable fluorescence characteristics with one or two emission wavelengths (515 and 575 nm) depending on the excitation wavelengths. Amido and carboxy groups on the AFDFM shell layer allow the formation of linkages with biomolecules for biological imaging or molecule detection, opening opportunities for biomedical applications.