Glioblastoma (GBM) is one of the most aggressive central nervous system tumors, accounting for nearly 49 % of all intracranial neoplasms [1]. Despite advances in chemotherapy and radiotherapy, the therapeutic outcome for GBM patients is often dismal, primarily due to the tumor's intrinsic resistance to conventional treatments and the high recurrence rate post-therapy [2]. Furthermore, the existence of physiological barriers including the blood-brain barrier (BBB) and blood-brain tumor barrier (BBTB) further limit the deep penetration of chemotherapeutic drugs such as carmustine, nimustine, cisplatin, and cyclophosphamide into the GBM tumor [3,4]. Thus, the development of novel therapeutic agents that can effectively target and eradicate GBM cells is therefore of paramount importance.

In this respect, animal venom-derived peptides displaying a remarkable molecular diversity have emerged as a reliable resource for identifying novel therapeutics [5]. In order to realize the properties of predation and self-defense of venomous animals, many highly active and structurally-diverse venom peptides have emerged during the natural evolution process [6,7]. Several studies have reported venom-derived peptides with potential anti-glioblastoma activities. For example, Chlorotoxin (CTX) is a scorpion venom peptide composed of 36 amino acids isolated from an Israeli scorpion Leiurus quinquestriatus. It can effectively block the unique glioma-specific Chloride ion Channel (GCC) current of GBM cells, thereby inhibiting the migration and infiltration of GBM cells, thereby achieving targeted anti-glioma effects [8]. Another CTX-like peptide, AaCtx, purified from the venom of the yellow scorpion Androctonus australis, displayed anti-GBM effects, hence blocking invasion and migration of GBM cells [9]. Furthermore, AaTs-1 from this scorpion venom modulated the formyl peptide receptor 1 (FPRL-1) to activate calcium flux in GBM, thereby inhibiting tumor cell proliferation [10]. However, to date, there are no animal venom peptide-based drugs that have been approved by the FDA for cancer treatment. Compared with small molecule drugs, peptides may lack sufficient cell specificity, have a short half-life, and a poor solubility, which limits their development. Therefore, with proper modification and delivery, the development of a new generation of peptides with enhanced stability, cell targeting and effective cellular internalization, is an important aim in the field of peptide research and future therapeutics [11].

Over the past few decades, researchers have articulated a number of strategies to deliver drugs across the BBB such as using a hyperosmolar mannitol solution to transiently permeabilize the BBB [12], as well as modification of chemotherapeutics to become more hydrophobic [13], or building endogenous transport systems to enhance the penetration of chemotherapeutic drugs [14,15]. In this respect, the polyamidoamine (PAMAM) dendrimer is one of the most studied dendritic macromolecules which has been widely used in biomedical research due to its various favorable properties, including hyperbranched, monodisperse, three-dimensional spatial and host-guest entrapment properties [16]. PAMAM dendrimer synthesized with a definitive size (3–12 nm) can be obtained by means of its ultra-fine particle size, which enables GBM drug delivery [17]. In addition, some terminal group modifications are utilized to diminish the cationic charge and enhance the targeting capability of PAMAM [18].

It has been reported that abnormal glycosylation on the surface of cancer cells is one of the characteristics of many cancers [19]. In this respect, sialic acid, an anionic monosaccharide, was significantly elevated in a variety of cancer cells, including GBM cells [20,21]. 4-(bromomethyl) phenylboronic acid(PBA)derivatives are synthetic mimics of naturally occurring lectins, which selectively recognize sialic acid residues at pH 7.4 to target cancer cells [22]. Deshayes et al., used PBA-PEG-PLGA to effectively enhance the uptake of drugs by targeting sialic acid epitopes on the surface of cancer cells [23], whereas Ji et al., employed PBA-modified polyethyleneimine nanoparticles (PEI-PBA) to significantly enhance in vitro gene transfection capacity [24].

In the present study, a venom-derived peptide Ctri9495 (C9) was isolated from the scorpion Chaerilus tricostatus and characterized. It was found to have no anti-proliferative activity against glioblastoma cell lines due to its non-specific membrane binding activity. However, a small nanoparticle drug delivery platform was developed by conjugating peptide C9 to a generation 5 PAMAM dendrimer (G5 PAMAM) with a terminal PBA group modification. Following successful binding to tumor cell surface sialic acid and endocytosis, as well as endolysosome formation, the complex G5C9 displayed a remarkable anti-glioblastoma activity both in vitro and in vivo; this occurred via cell cycle arrest, induction of apoptosis and inhibition of migration. These results offer a novel modality to target, penetrate tumor cells and engage with essential intracellular tumor targets using venom-derived peptides. We further revealed the mechanism of action of G5C9 against glioblastoma. Apart from the downregulation of the PI3K/AKT signaling pathway, inhibition of mTORC1 and subsequent nuclear translocation of transcription factor EB (TFEB) resulted in elevated lysosomal biogenesis and autophagy.