1. Introduction
Breast cancer is the most common malignant tumor worldwide and the leading cause of female mortality.[1,2] More than half a million deaths caused by breast cancer were recorded in 2020 by the Global Cancer Center at WHO.[3] This histological pathology implies the appearance of adenocarcinoma in mammary glands.[4] Current therapy for breast cancer consists of invasive tumor surgical resection and systemic chemotherapy treatment.[5] However, non-specific chemo-pharmacologic treatments induce several drastic side effects.[6,7] Today, nanomedicine is focusing on designing novel and smart therapies to increase the efficiency of breast cancer treatment.[8-10]
Glucose oxidase (GOx) enzyme activity has been recently proposed for cancer nanomedicine applications. GOx, an intracellular enzyme fromAspergillus niger is widely used in glucose determination, fermentation industry, biosensors fabrication, and as a potential antibiotic.[11,12] This enzyme catalyzes glucose oxidation to produce hydrogen peroxide and gluconolactone. In a tumor environment, the GOx activity reduces, both available glucose and molecular oxygen, essential compounds for cell metabolism. In addition, GOx produces oxidative stress generating hydrogen peroxide, killing tumor cells.[13] Different designs of GOx enzyme systems have been recently developed for cancer therapy, including several mono and multimodal vesicles, polymer dots, and magnetic nanoparticles.[14-17]
Nanoparticle specific-targeting is an emerging field to deliver cytotoxic activity to tumor cells selectively. The specific anticancer-drug delivery increases the treatment effectiveness and reduces the drastic side effects.[18] A diversity of nanosystems, such as polymer, protein, metallic, organic, and inorganic nanoparticles, has been proposed for biomedical applications.[19] Protein cages based on viral capsids, or virus-like particles (VLPs), are interesting nanosystems that have been proposed as nanocarriers for delivering anticancer therapies to specific tumor cells.[20,21] VLPs are widely used in vaccine technology and have recently recently been proposed as nanoplatforms as carriers of drugs for different biomedical therapies.[22-25] VLPs can be derived from native viruses or obtained by recombinant technology. After removing the genetic material, the purified monomeric coat protein is self-assembled under certain conditions forming hollow nanoparticles. Self-assembly property is used to confine or encapsulate several cargo molecules producing well-defined symmetry and homogenous size nanoparticles. The VLPs are highly stable in carrying and delivering cargo molecules, are biocompatible and biodegradable, and show low toxicity.[26,27] The surface of VLPs can be functionalized with a diversity of ligands to be specifically targeted to cells and tissues [28,29] making smarter and more efficient therapies. In addition, the suspension of VLPs is highly stable in biological fluids.
VLPs can contain active enzymes, and the arrangement is called an enzymatic nanoreactor.[22] Improved catalytic properties have been reported for virus-based enzymatic nanoreactors.[30-32] VLP-based enzymatic nanoreactors containing cytochrome P450 activity have been proposed for prodrug activation in breast cancer therapy.[33-35] The protein cage structure protects the catalytic molecule from protease degradation and decreases enzyme recognition by the immune system conferring a better catalytic performance.[36-38] Moreover, the intrinsic porous structure of the VLP-based nanoreactors can allow the substrates and products to flow through the system.[39-41]
This work encapsulated glucose oxidase in VLPs from Brome Mosaic Virus (BMV). The catalytic properties of the enzymatic nanoreactors were analyzed, and their effect on tumor cell lines was determined.