Fluorescent Peptides Internalize HeLa Cells and Kill Multidrug-Resistant Clinical Bacterial Isolates

Area of Science:

• Medicinal Chemistry
• Antimicrobial Peptides
• Cancer Therapeutics

Background:

• Palindromic antimicrobial peptides (PAMs) are versatile scaffolds for developing anticancer agents.
• Fluorolabeling allows for tracking and studying peptide behavior in biological systems.
• Understanding the mechanism of action of novel anticancer agents is crucial for therapeutic development.

Purpose of the Study:

• To synthesize and characterize fluorolabeled palindromic peptides derived from the RWQWRWQWR sequence.
• To evaluate the antibacterial and anticancer activities of these novel peptide conjugates.
• To investigate the role of cellular internalization in the mechanism of action of these peptides.

Main Methods:

• Synthesis of fluorolabeled peptides using fluorescent probes (2-Aminobenzoyl, 5(6)-Carboxyfluorescein, Rhodamine B).
• Analysis of peptide purity and isomer presence using RP-HPLC.
• Determination of minimum inhibitory concentration (MIC) against bacterial strains.
• Assessment of cytotoxic effects on cancer cell lines (HeLa, MCF-7) using IC50 values.
• Morphological analysis to identify apoptosis-induced cell death.

Main Results:

• Fluorolabeled peptides, particularly those with Rhodamine B, showed varying antibacterial activity against Gram-positive and Gram-negative bacteria, including resistant strains.
• Several fluorolabeled peptides exhibited significant concentration-dependent cytotoxicity against HeLa and MCF-7 cancer cells, inducing apoptosis.
• Rhodamine-labeled peptides displayed comparable cytotoxicity to unlabeled analogues, suggesting cellular internalization is a key step.
• Isomer formation was observed in some Rhodamine B-conjugated peptides, dependent on the peptide sequence.

Conclusions:

• Fluorolabeled palindromic peptides are effective antibacterial and anticancer agents.
• Cellular internalization appears critical for the cytotoxic mechanism of these peptides, predominantly inducing apoptosis.
• These findings support the potential of functionalized PAMs for targeted cancer therapy and drug delivery systems.