Increased the TMZ concentration in brain by poly(2-ethyl-2-oxazoline) conjugated temozolomide prodrug micelles for glioblastoma treatment

Strategies increasing the effectiveness of temozolomide at various levels of anti-GBL therapy

Glioblastoma (GBL) is the most common (60-70% of primary brain tumours) and the most malignant of the glial tumours. Although current therapies remain palliative, they have been proven to prolong overall survival. Within an optimal treatment regimen (incl. surgical resection, radiation therapy, and chemotherapy) temozolomide as the current anti-GBL first-line chemotherapeutic has increased the median overall survival to 14-15 months, and the percentage of patients alive at two years has been reported to rise from 10.4% to 26.5%. Though, the effectiveness of temozolomide chemotherapy is limited by the serious systemic, dose-related side effects. Therefore, the ponderation regarding novel treatment methods along with innovative formulations is crucial to emerging the therapeutic potential of the widely used drug simultaneously reducing the drawbacks of its use. Herein the complex temozolomide application restrictions present at different levels of therapy as well as, the currently proposed strategies aimed at reducing those limitations are demonstrated. Approaches increasing the efficacy of anti-GBL treatment are addressed. Our paper is focused on the most recent developments in the field of nano/biomaterials-based systems for temozolomide delivery and their functionalization towards more effective blood-brain-barrier crossing and/or tumour targeting. Appropriate designing accounting for the physical and chemical features of formulations along with distinct routes of administration is also discussed. In addition, considering the multiple resistance mechanisms, the molecular heterogeneity and the evolution of tumour the purposely selected delivery methods, the combined therapeutic approaches and specifically focused on GBL cells therapies are reviewed.

Cell-Derived Vesicles for Nanoparticles' Coating: Biomimetic Approaches for Enhanced Blood Circulation and Cancer Therapy

Cancer nanomedicines are designed to encapsulate different therapeutic agents, prevent their premature release, and deliver them specifically to cancer cells, due to their ability to preferentially accumulate in tumor tissue. However, after intravenous administration, nanoparticles immediately interact with biological components that facilitate their recognition by the immune system, being rapidly removed from circulation. Reports show that less than 1% of the administered nanoparticles effectively reach the tumor site. This suboptimal pharmacokinetic profile is pointed out as one of the main factors for the nanoparticles' suboptimal therapeutic effectiveness and poor translation to the clinic. Therefore, an extended blood circulation time may be crucial to increase the nanoparticles' chances of being accumulated in the tumor and promote a site-specific delivery of therapeutic agents. For that purpose, the understanding of the forces that govern the nanoparticles' interaction with biological components and the impact of the physicochemical properties on the in vivo fate will allow the development of novel and more effective nanomedicines. Therefore, in this review, the nano-bio interactions are summarized. Moreover, the application of cell-derived vesicles for extending the blood circulation time and tumor accumulation is reviewed, focusing on the advantages and shortcomings of each cell source.

Polymeric and small molecule-conjugates of temozolomide as improved therapeutic agents for glioblastoma multiforme

Temozolomide (TMZ), an imidazotetrazine, is a second-generation DNA alkylating agent used as a first-line treatment of glioblastoma multiforme (GBM). It was approved by FDA in 2005 and declared a blockbuster drug in 2008. Although TMZ has shown 100% oral bioavailability and crosses the blood-brain barrier effectively, however it suffers from limitations such as a short half-life (∼1.8 h), rapid metabolism, and lesser accumulation in the brain (∼10-20%). Additionally, development of chemoresistance has been associated with its use. Since it is a potential chemotherapeutic agent with an unmet medical need, advanced delivery strategies have been explored to overcome the associated limitations of TMZ. Nanocarriers including liposomes, solid lipid nanoparticles (SLNs), nanostructure lipid carriers (NLCs), and polymeric nanoparticles have demonstrated their ability to improve its circulation time, stability, tissue-specific accumulation, sustained release, and cellular uptake. Because of the appreciable water solubility of TMZ (∼5 mg/mL), the physical loading of TMZ in these nanocarriers is always challenging. Alternatively, the conjugation approach, wherein TMZ has been conjugated to polymers or small molecules, has been explored with improved outcomes in vitro and in vivo. This review emphasized the practical evidence of the conjugation strategy to improve the therapeutic potential of TMZ in the treatment of glioblastoma multiforme.

Poly(2-oxazoline) - Ferrostatin-1 drug conjugates inhibit ferroptotic cell death

Ferroptosis is a form of non-apoptotic iron induced cell death mechanism implicated in neurodegeneration, yet can be ameliorated with potent radical scavengers such as ferrostatin-1 (Fer-1). Currently, Fer-1 suffers from low water solubility, poor biodistribution profile and is unsuitable for clinical application. Fer-1 polymer-drug conjugates (PDCs) for testing as an anti-ferroptosis therapeutic candidate have yet to be described. Here, we report the synthesis and characterization of a library of water-soluble Fer-1 based poly(2-oxazoline)-drug conjugates. The cationic ring opening polymerization (CROP) of water-soluble 2-oxazoline monomers, and a novel protected aromatic aldehyde 2-oxazoline (DPhOx), produced defined copolymers, which after deprotection were available for modification with Fer-1 via reductive amination and Schiff base chemistry. The conjugates were tested for their activity against RSL3-induced ferroptosis in vitro, and first structure-activity relationships were established. Irreversibly conjugated Fer-1 PDCs possessing an arylamine structural motif showed a greatly increased anti-ferroptosis activity compared to reversibly (Schiff base) linked Fer-1. Overall, this work introduces the first active ferrostatin-PDCs and a new highly tuneable poly(2-oxazoline)-based PDC platform, which provides access to next generation polymeric nanomaterials for anti-ferroptosis applications.

Temozolomide: an Overview of Biological Properties, Drug Delivery Nanosystems, and Analytical Methods

Temozolomide (TMZ) is an imidazotetrazine prodrug used to treat glioblastoma multiforme. Its physicochemical prop-erties and small size confer the ability to cross the blood-brain barrier. The antitumor activity depends on pH-dependent hydrolysis of the methyldiazonium cation, which is capable of methylating purine bases (O6-guanine; N7-guanine, and N3-adenine) and causing DNA damage and cell death. TMZ is more stable in acidic media (pH ≤ 5.0) than in basic media (pH ≥ 7.0) due to the protonated form that minimizes the catalytic process. Because of this, TMZ has high oral bioavailability, but it has a half-life of 1.8 h and low brain distribution (17.8%), requiring a repeated dos-ing regimen that limits its efficacy and increases adverse events. Drug delivery Nanosystems (DDNs) improve the phys-icochemical properties of TMZ and may provide controlled and targeted delivery. Therefore, DDNs can increase the efficacy and safety of TMZ. In this context, to ensure the efficiency of DDNs, analytical methods are used to evaluate TMZ pharmacokinetic parameters, encapsulation efficiency, and the release profile of DDNs. Among the methods, high-performance liquid chromatography is the most used due to its detection sensitivity in complex matrices such as tissues and plasma. Micellar electrokinetic chromatography features fast analysis and no sample pretreatment. Spec-trophotometric methods are still used to determine encapsulation efficiency due to their low cost, despite their low sen-sitivity. This review summarizes the physicochemical and pharmacological properties of free TMZ and TMZ-loaded DDNs. In addition, this review addresses the main analytical methods employed to characterize TMZ in different ma-trices.

Progress and Viewpoints of Multifunctional Composite Nanomaterials for Glioblastoma Theranostics

The most common malignant tumor of the brain is glioblastoma multiforme (GBM) in adults. Many patients die shortly after diagnosis, and only 6% of patients survive more than 5 years. Moreover, the current average survival of malignant brain tumors is only about 15 months, and the recurrence rate within 2 years is almost 100%. Brain diseases are complicated to treat. The reason for this is that drugs are challenging to deliver to the brain because there is a blood–brain barrier (BBB) protection mechanism in the brain, which only allows water, oxygen, and blood sugar to enter the brain through blood vessels. Other chemicals cannot enter the brain due to their large size or are considered harmful substances. As a result, the efficacy of drugs for treating brain diseases is only about 30%, which cannot satisfy treatment expectations. Therefore, researchers have designed many types of nanoparticles and nanocomposites to fight against the most common malignant tumors in the brain, and they have been successful in animal experiments. This review will discuss the application of various nanocomposites in diagnosing and treating GBM. The topics include (1) the efficient and long-term tracking of brain images (magnetic resonance imaging, MRI, and near-infrared light (NIR)); (2) breaking through BBB for drug delivery; and (3) natural and chemical drugs equipped with nanomaterials. These multifunctional nanoparticles can overcome current difficulties and achieve progressive GBM treatment and diagnosis results.

Visible Light and Glutathione Dually Responsive Delivery of a Polymer-Conjugated Temozolomide Intermediate for Glioblastoma Chemotherapy

Temozolomide (TMZ) is a prodrug of 5-(3-methyltriazene-1-yl)imidazole-4-carboxamide (MTIC, short-lived) and used as a first-line therapy drug for glioblastoma multiforme (GBM). However, little progress has been made in regulating the kinetics of TMZ to MTIC degradation to improve the therapeutic effect, particularly in the case of TMZ-resistant GBM. In this work, we introduced a strategy to cage MTIC by N-acylation of the triazene moiety to boost the MTIC stability, designed a diblock copolymer-based MTIC prodrug installed with a disulfide linkage, and achieved self-assembled polymer micelles without the concern of MTIC leakage under physiological conditions. Polymer micelles could be induced to disassemble by stimuli factors such as glutathione (GSH) and visible light irradiation through thiol/sulfide exchange and homolytic sulfide scission mechanisms, which contributed to MTIC release in GSH-dependent and GSH-independent pathways. The in vitro results demonstrated that microenvironment-responsive polymeric micelles benefited the suppression of both TMZ-sensitive and TMZ-resistant GBM cells. The chemistry of polymer-MTIC prodrug provided a new option for TMZ-based glioma treatment.

Recent developments in selenium-containing polymeric micelles: prospective stimuli, drug-release behaviors, and intrinsic anticancer activity

Selenium is capable of forming a dynamic covalent bond with itself and other elements and can undergo metathesis and regeneration reactions under optimum conditions. Its dynamic nature endows selenium-containing polymers with striking sensitivity towards some environmental alterations. In the past decade, several selenium-containing polymers were synthesized and used for the preparation of oxidation-, reduction-, and radiation-responsive nanocarriers. Recently, thioredoxin reductase, sonication, and osmotic pressure triggered the cleavage of Se-Se bonds and swelling or disassembly of nanostructures. Moreover, some selenium-containing nanocarriers form oxidation products such as seleninic acids and acrylates with inherent anticancer activities. Thus, selenium-containing polymers hold promise for the fabrication of ultrasensitive and multifunctional nanocarriers of radiotherapeutic, chemotherapeutic, and immunotherapeutic significance. Herein, we discuss the most recent developments in selenium-containing polymeric micelles in light of their architecture, multiple stimuli-responsive properties, emerging immunomodulatory activities, and future perspectives in the delivery and controlled release of anticancer agents.