{'fraction_non_alphanumeric': 0.028659611992945325, 'fraction_numerical': 0.007495590828924162, 'mean_word_length': 5.981538461538461, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
DNA‐binding peptide dendrimer for efficient and selective intracellular delivery

Dendrimeric peptides or peptide dendrimers are branched peptides with multiple peptidyl units. Multiple antigen peptides (MAPs) are examples of dendrimeric peptides first introduced in 1988 by our laboratory as immunogens for producing monoclonal and polyclonal antibodies. We also designed antimicrobial dendrimeric peptides, such as D4R, using a tetrapeptide RLYR which contains a ChC‐motif (cationic‐hydrophobic‐cationic) found in the naturally‐occurring antimicrobial peptides such as tachyplesins and protegrins. Advantages of D4R as a short‐chain, tetra‐branched peptide dendrimer include its short preparation time (a few hours), its polycationic, low membranolytic activity to human red blood cells, and high proteolytic stability. Here, we show that D4R is also a cell‐penetrating and an intracellular DNA‐binding peptide dendrimer. Using solid‐phase synthesis, we exploited different chemistries to attach tags or small molecules to the α‐ or ɛ‐amino groups of lysine to form a tetra‐branched dendrimer with four chains of RLYR. An example is D4R‐f, a C‐terminal 5‐FAM‐labeled D4R which we showed that it can enter living cells through endocytosis‐independent mechanisms as determined by using epi‐fluorescence microscopy. Furthermore, we showed that D4R‐f is distributed in different intracellular organelles during different stages of the cell cycles and colocalizes with nuclear DNA in cells undergoing mitosis. Using agarose gel shift assay, we showed that D4R binds to double‐stranded DNA. Co‐incubation of D4R with DNA showed resistance against DNase‐mediated digestion. The control linear 16‐residue peptide with four tandemly repeating RLYR units was not cell‐penetrating like D4R. Modifying the ChC motifs of the short‐chain peptide dendrimers produced different results, suggesting that the RLYR motif is tunable. Taken together, this study highlights D4R as a prototypic DNA‐binding peptide dendrimer which penetrates into living cells through endocytosis‐independent uptake mechanisms. Our work also suggests the potentials of short‐chain DNA‐binding peptide dendrimers as a lead to design anti‐mitotic agents and a convenient new tool for non‐viral gene delivery.