The development of smart drug delivery systems capable of responding to the unique physiological characteristics of tumors has emerged as a pivotal strategy in modern cancer therapy. This study introduces a pH-responsive, RGD-functionalized peptide nanoparticle system designed to enhance tumor-specific drug delivery and improve therapeutic outcomes. The amphiphilic peptide LKR, with the sequence Ac-Leu-Leu-Leu-Leu-Leu-Leu-Lys-Lys-Lys-Gly-Arg-Gly-Asp-Ser-NH₂, was synthesized using solid-phase peptide synthesis and characterized via HPLC and mass spectrometry, confirming high purity (>95%). At neutral pH (7.4), LKR spontaneously self-assembled into uniform spherical nanoparticles (~50–60 nm in size) as confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). These nanoparticles efficiently encapsulated doxorubicin (Dox), forming Dox/LKR complexes with an average particle size of 40–140 nm.
A critical feature of this system is its responsiveness to acidic microenvironments. When the pH was reduced to 6.0—mimicking the extracellular milieu of solid tumors—the nanoparticles underwent structural disintegration. DLS analysis revealed a significant increase in particle size distribution, with a new peak appearing at 220–460 nm, indicating swelling and fragmentation. TEM imaging showed complete loss of spherical morphology, with ruptured and fragmented structures observed after 24 hours. Circular dichroism (CD) analysis further demonstrated a shift from β-sheet conformation at pH 7.4 to dominant random coil structure at pH 6.0, suggesting protonation-induced disruption of intermolecular interactions. This change in secondary structure likely drives the electrostatic repulsion between charged lysine and arginine residues, leading to nanoparticle expansion and burst release of Dox.
In vitro drug release studies confirmed the pH-dependent behavior: only ~10% of Dox was released at pH 7.4 over 96 hours, while over 80% was released within the same period at pH 6.0. The rapid release profile under acidic conditions highlights the potential for site-specific drug activation. Cellular uptake assays using flow cytometry and confocal microscopy revealed significantly enhanced internalization of Dox-loaded nanoparticles in HepG2 hepatocellular carcinoma cells compared to normal LX2 cells. Fluorescence intensity was markedly higher in tumor cells, particularly after 2 hours of incubation, indicating preferential accumulation driven by both RGD-mediated targeting and increased membrane permeability in acidic environments.
In vivo evaluation was performed using BALB/c mice bearing subcutaneous H22 hepatoma xenografts. Animals were treated intraperitoneally with saline, free Dox (5 mg/kg), empty LKR nanoparticles (25 mg/kg), or Dox-loaded LKR nanoparticles every 48 hours for 14 days. Tumor volume was measured every two days. By day 15, the Dox/LKR group exhibited the most pronounced antitumor effect, with tumor growth inhibition reaching 77%. Histological examination via H&E staining revealed extensive necrosis and apoptosis in tumor tissues from the Dox/LKR group, consistent with effective drug delivery.Galectin-9 Antibody Protocol Importantly, no significant body weight loss was observed, indicating low systemic toxicity.FAK Antibody supplier In contrast, the free Dox group showed greater toxicity, underscoring the protective role of the nanoparticle carrier.PMID:34599941
This study demonstrates that RGD-modified, pH-sensitive peptide nanoparticles offer a robust platform for targeted cancer therapy. By leveraging the acidic tumor microenvironment as a trigger and integrin overexpression as a targeting mechanism, this system achieves spatial precision in drug delivery. The self-assembly capability, biocompatibility, and tunable responsiveness make it highly suitable for clinical translation. Future work will focus on optimizing dosing regimens and evaluating combination therapies to further enhance efficacy against resistant cancers.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com