Magnetic nanoparticle composite with a cobalt ferrite (CoFe₂O₄, (CF)) core and an apatite (Ap) coating was synthesized using a biomineralization process in which a modified simulated body fluid (1.5SBF) solution is the source of the calcium phosphate for the apatite formation. The core–shell structure formed after the citric acid–stabilized cobalt ferrite (CFCA) particles were incubated in the 1.5 SBF solution for 1 week. The mean particle size of CFCA-Ap is about 750 nm. A saturation magnetization of 15.56 emug^-1 and a coercivity of 1808.5 Oe were observed for the CFCA-Ap obtained. Bovine serum albumin (BSA) was used as the model protein to study the adsorption and release of the proteins by the CFCA-Ap particles. The protein adsorption by the CFCA-Ap particles followed a more typical Freundlich than Langmuir adsorption isotherm. The BSA release as a function of time became less rapid as the CFCA-Ap particles were immersed in higher pH solution, thus indicating that the BSA release is dependent on the local pH.

Drug delivery particles in which the release of biomolecules is triggered by a magnetic simulant have attracted much attention and may have great potential in the fields of cancer therapy and tissue regenerative medicine. In this study, we have prepared magnetic Mn–Zn ferrite ((Mn,Zn)Fe₂O₄) (MZF) nanoparticles coated with chitosan-g-N-isopropylacrylamide (Chi-g-NIPAAm) polymer (MZF@Chi-g-NIPAAm) to deliver the anticancer drug (Doxorubicin, DOX) and bioactive proteins (Bone morphogenic protein (BMP-2)-immobilized bovine serum albumin (BSA)) (P//MZF@Chi-g-NIPAAm) and be used as chemo-hyperthermia and vector delivering biomolecules. For these purposes, we first show that the as-prepared MZF@Chi-g-NIPAAm particles exhibit super paramagnetic behavior and under certain conditions, they can act as a heat source with a specific absorption rate (SAR) of 34.88 W g⁻¹. Under acidic conditions and in the presence of AMF, the fast release of DOX was seen at around 58.9% within 20 min. In vitro evaluations indicated that concurrent thermo-chemotherapy treatment by DOX-MZF@Chi-g-NIPAAm using AMF had a better antitumor effect, compared with those using either DOX or DOX-MZF@Chi-g-NIPAAm without AMF (89.02% of cells were killed as compared to 71.82% without AMF exposure). Up to 28.18% of the BSA (used as the model protein to determine the controlled release) is released from the P//MZF@Chi-g-NIPAAm particles under AMF exposure for 1 h (only 17.31% was released without AMF). These results indicated that MZF@Chi-g-NIPAAm particles could be used to achieve hyperthermia at a precise location, effectively enhancing the chemotherapy treatments, and have a promising future as drug or bioactive delivering molecules for cancer treatment and cartilage or bone regenerative applications.