Co-delivery of temozolomide and quercetin with folic acid-conjugated exosomes in glioblastoma treatment

<b>Aim:</b> The study aims to improve glioblastoma multiforme (GBM) treatment by combining temozolomide (TMZ) and quercetin (Qct), using folic acid (FA)-conjugated exosomes to overcome TMZ resistance and enhance blood-brain barrier (BBB) penetration.<b>Methods:</b> Exosomes were isolated and after characterizing and modifying their surfaces with FA, drug loading of TMZ and Qct into exosomes was done. <i>In vitro</i> assays, including cell viability tests, RT-PCR, Western-blotting and flow-cytometry, were performed using U87MG and U251MG GBM cell lines. <i>In vivo</i> analysis included administering exosome-drug formulations to glioblastoma-bearing Wistar rats, monitored through optical imaging and PET scans, followed by post-mortem immunohistochemistry and histological examination.<b>Results:</b> The results showed successful exosome isolation and FA conjugation, with drug release studies indicating accelerated release of TMZ and Qct in acidic conditions, enhancing cytotoxicity. Immunofluorescence indicated greater exosome uptake in GBM cells due to FA conjugation. Cell viability assays demonstrated increased toxicity of the combination therapy, correlating with elevated apoptosis. <i>In vivo</i> studies revealed significant tumor size reduction, alongside increased apoptosis and reduced angiogenesis, particularly in the TMZ-Qct-Exo-FA group.<b>Conclusion:</b> FA-conjugated exosomes loaded with TMZ and Qct represent a promising strategy to enhance GBM treatment efficacy by improving drug delivery, apoptosis induction and inhibiting the PI3K/Akt/mTOR pathway.