Abstract
Recently, crosslinked fibroin nanoparticles (FNP) using the crosslinker 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) or the polymer poly(ethylenimine) (PEI) have been developed and showed potentials as novel drug delivery systems. Thus, this study further investigated the biological properties of these crosslinked FNP by labeling them with fluorescein isothiocyanate (FITC) for in vitro studies. All formulations possessed a mean particle size of approximately 300 nm and a tunable zeta potential (−20 to + 30 mV) dependent on the amount/type of crosslinkers. The FITC-bound FNP showed no significant difference in physical properties compared to the blank FNP. They possessed a binding efficacy of 3.3% w/w, and no FITC was released in sink condition up to 8 h. All formulations were colloidal stable in the sheep whole blood. The degradation rate of these FNP in blood could be controlled depending on their crosslink degree. Moreover, no potential toxicity in erythrocytes, Caco-2, HepG2, and 9L cells was noted for all formulations at particle concentrations of < 1 mg/mL. Finally, all FNP were internalized into the Caco-2 cells after 3 h incubation. The uptake rate of the positively charged particles was significantly higher than the negatively charged ones. In summary, the crosslinked FNP were safe and showed high potentials as versatile systems for biomedical applications.
Highlights
Fibroin, a fibrous protein commonly extracted from the domestic silkworm Bombyx mori silk, has gained increasing attention and focused research in various biomedical applications [1,2,3,4,5,6,7]
To track the particles in biological systems, fibroin nanoparticles (FNP) were labeled with fluorescein isothiocyanate (FITC), a xanthene dye
FITC isothiocyanate groups could react with fibroin residual amine groups to form thioamide covalent bonds
Summary
A fibrous protein commonly extracted from the domestic silkworm Bombyx mori silk, has gained increasing attention and focused research in various biomedical applications [1,2,3,4,5,6,7] Amongst several platforms such as films [8,9], hydrogels [10,11,12], tablets [13], scaffolds [14,15,16], and microparticles [17,18], fibroin nanoparticles (FNP) are the most utilized systems for drug delivery purposes [4,19,20]. In most studies, unmodified FNP are popularly formulated using desolvation method, in which the aqueous solution of regenerated fibroin is mixed homogeneously with an organic solvent to yield insoluble submicron particles [19,21,22,23] This method creates unmodified FNP with obvious limitations that may hinder their versatility in clinical uses. The fact that the cell membrane possesses a negative charge hinders the versatility of the system, especially in cellular binding, internalization, and mucoadhesiveness properties [30]
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