Electrostatics modulates the interactions of CPPs with the corresponding cell surface. Therefore, for the design of the amino acid side chain sequences, we reverse-engineered the spatial electrostatic potential distribution of the previously designed peptides with cell penetration ability. The spatial electrostatic fingerprints of the earlier designed peptides were generated as described previously. The reverse-engineered sequences with a shorter (7-mer) chain length were compared to the previous designs through multiple iterations of amino acid sequences. Their respective electrostatic profiles were used for the design of four syndiotactic, cationic, amphipathic peptides with optimal sequence selection. These syndiotactic re-engineered amphipathic peptides (STRAPs) were tested for their ability to penetrate cells and deliver a small molecule (methotrexate). The amino acid constitutions of STRAP-1, STRAP-2, STRAP-3, and STRAP-4 are the same. However, STRAP-2 is the stereochemically reversed STRAP-1; similarly, STRAP-4 is the stereochemically reversed STRAP-3. The use of LDLD and DLDL stereochemical sequences in the design of STRAPs resulted in the differential electrostatic signatures for the same amino acid sequences. The designed peptides have a higher cellular uptake in TNBC cells (MDA-MB-231) than the standard control TAT peptide. They could penetrate cells by both active and passive processes, and their activity is not reduced in biological fluids (human plasma and bovine serum). Furthermore, the delivery of MTX as STRAP-MTX conjugates helped to overcome the drug resistance of the MDA-MB-231 cells under in vitro conditions. The delivery of the STARP-4-MTX conjugate in TNBC xenograft tumors was more effective in the reduction of both the tumor size and metastasis to the lungs, liver, spleen, and lymph nodes.

Electrostatics modulates the interactions of CPPs with the corresponding cell surface. Therefore, for the design of the amino acid side chain sequences, we reverse-engineered the spatial electrostatic potential distribution of the previously designed peptides with cell penetration ability. The spatial electrostatic fingerprints of the earlier designed peptides were generated as described previously. The reverse-engineered sequences with a shorter (7-mer) chain length were compared to the previous designs through multiple iterations of amino acid sequences. Their respective electrostatic profiles were used for the design of four syndiotactic, cationic, amphipathic peptides with optimal sequence selection. These syndiotactic re-engineered amphipathic peptides (STRAPs) were tested for their ability to penetrate cells and deliver a small molecule (methotrexate). The amino acid constitutions of STRAP-1, STRAP-2, STRAP-3, and STRAP-4 are the same. However, STRAP-2 is the stereochemically reversed STRAP-1; similarly, STRAP-4 is the stereochemically reversed STRAP-3. The use of LDLD and DLDL stereochemical sequences in the design of STRAPs resulted in the differential electrostatic signatures for the same amino acid sequences. The designed peptides have a higher cellular uptake in TNBC cells (MDA-MB-231) than the standard control TAT peptide. They could penetrate cells by both active and passive processes, and their activity is not reduced in biological fluids (human plasma and bovine serum). Furthermore, the delivery of MTX as STRAP-MTX conjugates helped to overcome the drug resistance of the MDA-MB-231 cells under in vitro conditions. The delivery of the STARP-4-MTX conjugate in TNBC xenograft tumors was more effective in the reduction of both the tumor size and metastasis to the lungs, liver, spleen, and lymph nodes.

Electrostatics modulates the interactions of CPPs with the corresponding cell surface. Therefore, for the design of the amino acid side chain sequences, we reverse-engineered the spatial electrostatic potential distribution of the previously designed peptides with cell penetration ability. The spatial electrostatic fingerprints of the earlier designed peptides were generated as described previously. The reverse-engineered sequences with a shorter (7-mer) chain length were compared to the previous designs through multiple iterations of amino acid sequences. Their respective electrostatic profiles were used for the design of four syndiotactic, cationic, amphipathic peptides with optimal sequence selection. These syndiotactic re-engineered amphipathic peptides (STRAPs) were tested for their ability to penetrate cells and deliver a small molecule (methotrexate). The amino acid constitutions of STRAP-1, STRAP-2, STRAP-3, and STRAP-4 are the same. However, STRAP-2 is the stereochemically reversed STRAP-1; similarly, STRAP-4 is the stereochemically reversed STRAP-3. The use of LDLD and DLDL stereochemical sequences in the design of STRAPs resulted in the differential electrostatic signatures for the same amino acid sequences. The designed peptides have a higher cellular uptake in TNBC cells (MDA-MB-231) than the standard control TAT peptide. They could penetrate cells by both active and passive processes, and their activity is not reduced in biological fluids (human plasma and bovine serum). Furthermore, the delivery of MTX as STRAP-MTX conjugates helped to overcome the drug resistance of the MDA-MB-231 cells under in vitro conditions. The delivery of the STARP-4-MTX conjugate in TNBC xenograft tumors was more effective in the reduction of both the tumor size and metastasis to the lungs, liver, spleen, and lymph nodes.