Abstract
Peptides are strings of approximately 2–50 amino acids, which have gained huge attention for theranostic applications in cancer research due to their various advantages including better biosafety, customizability, convenient process of synthesis, targeting ability via recognizing biological receptors on cancer cells, and better ability to penetrate cell membranes. The conjugation of peptides to the various nano delivery systems (NDS) has been found to provide an added benefit toward targeted delivery for cancer therapy. Moreover, the simultaneous delivery of peptide-conjugated NDS and nano probes has shown potential for the diagnosis of the malignant progression of cancer. In this review, various barriers hindering the targeting capacity of NDS are addressed, and various approaches for conjugating peptides and NDS have been discussed. Moreover, major peptide-based functionalized NDS targeting cancer-specific receptors have been considered, including the conjugation of peptides with extracellular vesicles, which are biological nanovesicles with promising ability for therapy and the diagnosis of cancer.
Highlights
IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
The complex tumor microenvironment (TME) of cancer exhibits various barriers including hypoxia, Mononuclear phagocytic system (MPS), occurrence of extravasation, cellular barriers, and drug efflux transporters, which are required to be overcome by the nano delivery systems (NDS)
A plethora of receptors have been reported to be associated with the malignant progression of cancer such as SSTR, integrin, transferrin, HER2, APN, Luteinizing Hormone-Releasing Hormone (LHRH), Epidermal Growth Factor Receptor (EGFR), Epithelial Cell Adhesion Molecule (EpCAM), and CD133, which have been utilized for developing the peptide-based functionalized NDS for targeted cancer therapy as well as diagnosis
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. How TME and hypoxia impede drug delivery? The TME consists of cellular components such as cancerous and noncancerous stromal cells, blood vessels, lymphatic vessels, and immune cells. Pharmaceutics 2021, 13, 1433 are generally affected by the growth of cancer cells [6]. The ECM in the TME is highly abundant, stiffer, and denser, forming another bottleneck to cancer therapy via shielding the cells from anti-cancer drugs. 2 of 19 of drug resistance in cancer cells [7]
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