Enzyme-sensitive cytotoxic peptide–dendrimer conjugates enhance cell apoptosis and deep tumor penetration

Abstract

Peptide nanodrugs have been developed as promising antitumor chemotherapeutics because they partially overcome the drawbacks of free peptide drugs, but insufficient tumor penetration and interference of peptide function limit their further application. In this work, we have developed multifunctional peptide conjugated dendrimers for improving tumor penetration, cancer cell-specific peptide delivery and anticancer ability. The cytotoxic peptide KLAK, cell-penetrating peptide TAT and matrix metalloproteinase 2 (MMP2)-sensitive peptide-poly(ethylene glycol) (PEG) were conjugated onto dendrimers by one-pot synthesis to gain PKT-S-PEG. The enzyme-sensitive properties and incubation stability of the dendrimers were investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Moreover, the cell viability, internalization pathway, mitochondria-regulated apoptosis and tumor penetration ability were measured by CCK-8 assay, lysosome colocalization, JC-1 assay and multicellular spheroid (MCS) experiments, respectively, in human primary glioblastoma (U87) cells. PKT-S-PEG showed significantly enhanced intracellular delivery performance, antitumor efficacy and deep tumor penetration capacity compared to a control non-MMP2 sensitive dendrimer PKT-C-PEG. The MMP2-overexpressing tumor microenvironment caused deprotection by removal of PEG, resulting in the decrease of particle size and exposure of KLAK and TAT, which enhanced tumor penetration, the entry of bioactive peptides into cells and subsequently the effective disruption of mitochondria. We believe that the peptide-dendrimer conjugate has potential for specific and effective delivery of peptide-based therapeutics into tumors.

<p>PAMAM Dendrimer Nanomolecules Utilized as Drug Delivery Systems for Potential Treatment of Glioblastoma: A Systematic Review</p>

“…For this reason, Liu and colleagues (2018) developed an acryl G4 PAMAM-NH 2 dendrimer conjugated to the cell-penetrating peptide, trans-activating transcriptional (TAT) activator peptide, along with PEG for delivery of the cytotoxic peptide (KLAKLAK) 2 (KLAK). 87 This conjugated dendrimer, denoted as PKT-S-PEG, was built according to a KLAK:TAT:PEG molar ratio of 50:10:40. KLAK is a peptide that specifically destroys the mitochondrial membrane of cells to elicit the apoptotic cascade for cell destruction.…”

“…PKT-S-PEG dendrimers penetrated to a depth of 70-80 μm within the tumor with high fluorescence intensity in the tumor interior whereas control dendrimers penetrated down to 30 μm, only, after an 8 hr incubation. 87 The investigation by Liu and colleagues (2018) has demonstrated the importance of enhancing tumor penetration as large tumors can be difficult to eradicate effectively without appropriate depth of therapeutic intervention. 87…”

“…87 The investigation by Liu and colleagues (2018) has demonstrated the importance of enhancing tumor penetration as large tumors can be difficult to eradicate effectively without appropriate depth of therapeutic intervention. 87…”

Dendrimers as Modulators of Brain Cells

“…The size shrinkage property benefits the cleaved dendrimers in the enhanced permeability and retention (EPR) effect, thus improving the cellular uptake of nanoparticles [ 132 , 133 ]. Liu et al also employed MMP2-sensitive peptide (GPLGIAGQ) in generation 4 PAMAM dendrimers for delivering cytotoxic peptide KLAK [ 118 ]. Unlike previous examples showing potential drawbacks in peptide-conjugated nanocarriers, Liu et al demonstrated the opposite proteolytic properties.…”

Nuclear singlet multimers (NUSIMERs) with long-lived singlet states

“…The generated structure allows for derivatization on terminal groups leading to a high density of various possible desired terminal modifications. This possibility has gained some interest especially in medical applications ranging from drug delivery39,40 and cytotoxica41–43 to fluorescence imaging 44. Apart from the aforementioned applications, possible modifications with gadolinium have been reported 45,46.…”