Magnetic nanoparticles (MNPs) with higher magnetization are highly desirable for targeted drug delivery (TDD) systems, as it helps accumulation of drug at the target site. However, functionalization of MNPs for drug binding reduces the magnetization which affects the efficacy of TDD. Herein we report direct functionalization of MNPs with (3-Aminopropyl)triethoxysilane (APTES) which preserves the magnetization. Grafting density estimated by TGA and BET analysis showed monolayer grafting of APTES on MNP surface. MNPs were comprehensively characterized by XRD, HR-TEM, SQUID-VSM and FTIR. Anti cancerous drug telmisartan (TEL) was loaded on monolayer APTES grafted MNPs. In-vitro controlled drug release and cytotoxicity study on PC-3 human prostate cancer cell line of TEL conjugated MNPs are also discussed. This functionalization strategy can be extended to other biomedical applications where higher magnetization is desired. (C) 2018 Elsevier Inc. All rights reserved.