Design of fluorescent and targeted nanoplatforms for potential anticancer applications: from chalcone derivatives to natural and repurposed agents

Despite decades of advanced research, cancer persists as one of the most pressing health challenges of our era. While progress in prevention, diagnosis, and innovative therapies has significantly improved clinical outcomes, the rising incidence of this disease and the limitations of current treatments underscore the urgent need for more effective and better tolerated strategies. This is particularly true for conventional chemotherapy, which is often plagued by a lack of specificity, leading to severe systemic toxicity. Further limitations include the development of resistance mechanisms, such as the overexpression of ATP-binding cassette transporters, and the inherently poor aqueous solubility of many potent drugs, which severely restricts their bioavailability and therapeutic potential. To address these complex issues, this doctoral research project focused on the rational design and development of innovative drug delivery systems (DDS) for anticancer therapy. The central aim was to engineer advanced nanoplatforms capable of enhancing solubility, bioavailability, and tumor-targeting specificity of both natural and newly synthesized anticancer agents. Particular emphasis was placed on developing fluorescent DDSs, thereby integrating therapeutic delivery with diagnostic capabilities (theranostics) for real-time tracking and monitoring. The initial phase of this multidisciplinary work involved the synthesis of a novel series of halogenated chalcones, a class of compounds recognized for their broad pharmacological profile, including anticancer and antiangiogenic activities. The derivatives were designed with different substitution patterns on aromatic ring A (Figure I.1.). The study investigated how the position of electron-withdrawing halogen substituents (ortho, meta, or para) could influence cytotoxicity against five cancer cell lines—follicular thyroid cancer (FTC-133), thyroid carcinoma (8305C), glioblastoma (U87), hepatocellular carcinoma (HEPG2), and osteosarcoma (U2OS)—and how these effects might correlate with their antitumor properties. The most active derivative (1e) was selected as a candidate for nanoformulation within lipid-based nanoparticles (NLCs) coated with fluorescent chitosan (FITC-CS), conceived as carriers able to improve delivery to tumor cells while also enabling real-time visualization through fluorescence imaging. The second part of the project addressed the critical solubility and bioavailability issues of rutin (RTN), a naturally occurring fluorescent flavonoid with strong antiangiogenic and anticancer potential. To enhance its pharmaceutical applicability, a supramolecular inclusion complex was developed using a novel, biocompatible PEGylated β-cyclodextrin polymer (β-CPCD) provided by the Centre for Defence Engineering and Physical Sciences at Cranfield University (Shrivenham, UK). This strategy was designed to improve RTN’s solubility and stability while maintaining its pharmacological activity, and to provide a suitable nanoplatform for combined therapeutic and diagnostic applications. Special attention was given to the assessment of its antiangiogenic activity in the zebrafish model, a well-established and reliable in vivo platform for studying angiogenesis and validating antiangiogenic compounds. The final part of this doctoral project focused on the development of chitosan-based nanoparticles (CS NPs) as carrier systems for breast cancer therapy, specifically intended for the encapsulation of a bicalutamide (BCL)/hydroxypropyl-β-cyclodextrin (HP-β-CD) inclusion complex. While BCL is an established antiandrogen in prostate cancer treatment, emerging preclinical and clinical evidence supports its potential repurposing for other androgen receptor-overexpressing tumors, such as AR-positive triple-negative breast cancer (AR+ TNBC). This formulation strategy was designed to achieve three primary objectives: ensure sustained and controlled release of BCL, enable selective tumor targeting through receptor-mediated mechanisms, and protect the drug from premature degradation. The inclusion of BCL in the form of a host-guest complex with HP-β-CD, rather than as a free drug, was required due to its extremely low aqueous solubility (<4 µg/mL), which prevents its direct incorporation into this type of carrier. CS NPs are generally more suitable for the encapsulation of hydrophilic compounds; therefore, the use of a cyclodextrin (CD), specifically HP-β-CD with its improved water solubility compared to the native form, allowed us to overcome this limitation. Moreover, once released from the NPs, BCL would be presented in a form more readily available for dissolution in biological fluids, thereby improving its subsequent bioavailability in physiological fluids. CS NPs were engineered via ionotropic gelation using HA as a cross-linking agent to actively target CD44 receptors, which are frequently overexpressed in aggressive tumors such as TNBC and are associated with poorer prognosis. Following the established methodology of this project, all nanosystems underwent comprehensive physicochemical and technological characterization to confirm their suitability as innovative delivery platforms. A distinctive feature of this work is the selection of three representative models: a newly synthesized compound (halogenated chalcone), a natural product (RTN), and a clinically used drug (BCL). The selection of these three models was not arbitrary but guided by a broader scientific rationale. Investing in the design and synthesis of novel molecules, such as chalcone-based derivatives inspired by natural scaffolds, remains essential for expanding the arsenal of anticancer agents. Natural substances, when properly formulated, can become valuable allies in oncology, potentially complementing drugs already in use in combined therapies. At the same time, drug repurposing represents a powerful strategy to accelerate the identification of new treatment options by exploiting existing pharmacological knowledge. These three case studies highlight a complementary strategy: designing new molecules inspired by natural scaffolds, drawing on nature, and repurposing existing drugs. When supported by innovative delivery technologies, such an integrated approach holds strong promise for advancing anticancer therapy toward more effective and better tolerated treatments.