Cell-penetrating peptides are short, positively charged (at neutral pH) peptides possessing the ability to penetrate into the cell. This property, combined with formation of complexes with other molecules, allows to use them as transporters crossing the biological membrane barrier. By means of covalent or electrostatic interactions cell-penetrating peptides bind to molecules and are efficiently internalized into the cell.

The aim of the study was comparison of two CPP peptides, C6M1 and HR9 as intracellular transporters. Both peptides non-covalently interact with quantum dots (CuInS₂/ZnS) and DNA (pEGFP-N1 plasmid DNA) forming stable CPP/QD and CPP/DNA complexes which are capable of entering human cells. The internalization studies revealed that  FITC-labeled CPP peptides are distributed evenly throughout the cytosol, mainly close to nuclear membrane. The transporting efficiency of CPP carriers of active biomolecules was proved with the internalization of plasmid and observed expression of GFP protein.
In addition it was proven that HR9/QD complex in contrast to C6M1/QD, can effectively enter human cells. Finally, the cytotoxic activity of peptides and prepared complexes were studied by WST-1 assay on normal and cancer cells, while microscopic analysis of cell structures has allowed an assessment of the physiological condition of the cell.

Provided results on the intracellular localization and the ability to transport functional molecules is essential from the point of view of further development and application the proposed system for therapy and medical diagnostics.

Acknowledgements

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