Preparation and Application of Novel Microspheres Possessing Autofluorescent Properties

Abstract

Fluorescent microspheres are widely used as biological tracers. In this study, uniformly sized chitosan microspheres crosslinked with glutaraldehyde (CG microspheres) and formaldehyde (CF microspheres) are successfully prepared by the Shirasu Porous Glass (SPG) membrane emulsification technique. Selectively reduced CG microspheres (SRCG microspheres) are obtained by NaBH4 reduction. These chitosan microspheres are found to exhibit fluorescent properties without conjugation to any fluorescent agent. The fluorescence color varies with different crosslinkers and can be modulated by further chemical reduction, whereas the fluorescence intensity can be controlled by tuning the particle size and degree of crosslinking. The autofluorescence of the microspheres is applied to study the phagocytosis of HepG2 cells using the microspheres as novel tracers. Quantitative and qualitative evaluations show that these chitosan microspheres serve as bright, inert, durable, and extremely photostable tracers.

Hollow Micro/Nanomaterials with Multilevel Interior Structures

“…[71][72][73][74][75][76][77][78][79][80][81][82] Ma and co-workers have used a microporous membrane emulsion technique to prepare various macroporous microspheres. [79][80][81][82] The membrane emulsification technique refers to the introduction of one liquid phase (such as an oil) into another immiscible liquid phase (such as water) through a porous membrane. The oil that passes through the porous membrane will be broken up into microdroplets and then is dispersed into the water to form an oil-in-water (O/W) emulsion.…”

Monodisperse Chitosan Microspheres with Interesting Structures for Protein Drug Delivery

“…Preparation of C-G Microspheres: Monodisperse chitosan microspheres were prepared according to a method previously described by Wei et al [6]. Surface treatement of the SPG membranes with KP-18C made the membranes relatively hydrophobic.…”

“…In addition to uniformity, the SPG membrane technique also enables the preparation of microspheres with a specific particle size by appropriate choice of the membrane pore size. [6] Therefore, the novel monodisperse chitosan microspheres with controllable size discussed here are promising systems for achieving better reproducibility, more repeatable release behavior, higher bioavailability, and passive targetability. The tunability of microsphere structural properties such as surface charge, cavity size, and wall porosity enables the modification of these systems to cater to specific requirements for use as protein drug carriers.…”

“…[6] These microspheres show remarkable autofluorescent properties that have been attributed to the n-p* transitions of C --N bonds in the Schiff bases formed during the crosslinking reaction. These traditional C-G microspheres are solid spherical objects without any pores on their surface.…”

An Anticoagulant Activity System Using Nanoengineered Autofluorescent Heparin Nanotubes

“…Similar results with the Schiff base effect have been reported previously. [21] The three fluorescent emission bands have been ascribed to n-p* transition of unsaturated C=N bonds from the Schiff base. To further prove this phenomenon, we carried out another experiment at the wavelength of 267 nm; the intensity at 532 nm was two times higher than that at 267 nm.…”