FITC characterization of a cathepsin B-responsive nanoprobe for report of differentiation of HL60 cells into macrophages.

A cathepsin B (Cat B)-responsive optical nanoprobe is designed and prepared for report of HL60 differentiation into macrophage. A peptide sequence FRFK is linked to fluorescein (FITC) via the distant amino group of its lysine and N-terminated with acrylic acid (AA) to yield a molecular fluorescent probe AA-FRFK (FITC). The molecular probe is further embedded in poly(lactic-co-glycolic acid) (PLGA) to form a fluorescent nanoprobe AA-FRFK (FITC)@PLGA. The resultant optical nanoprobe is degradable by lysosomal Cat B, which is expressed in macrophages with a level of 5-10 times of that in HL60 cells. As a result, a significant decrease in fluorescence intensity is associated with the differentiation process of HL60 to macrophage and can be used as an indication of the differentiation process. The findings may pave a way toward the development of a universal in vitro labeling strategy of exogenous stem cells for report of in vivo cell differentiation by a dual-mode imaging modality involving optical imaging and magnetic resonance imaging.

Evidence of speckle in extreme-UV lithography.

Based on reflective optics at 13.5 nm, extreme-UV lithography is the ultimate top-down technique to define structures below 22 nm but faces several challenges arising from the discrete nature of light and matter. Owing to the short wavelength, mask surface roughness plays a fundamental role in the increase of speckle pattern contrast, compromising the uniformity of the printed features. Herein, we have used a mask with engineered gradient surface roughness to illustrate the impact that speckle has on the resulting photoresist pattern. The speckle increases the photoresist roughness, but surprisingly, only when the mask surface roughness is well above existing manufacturing capabilities.