Anti-tumor drug doxorubicin has been successfully anchored onto MCM-41-type mesoporous silica nanoparticles (MSNs) with acid-cleavable citraconic bond to afford the hybrid Dox-MSN nanomedicine. "click chemistry" has been exploited as an effective method for doxorubicin conjugation. Under normal plasma pH conditions (pH = 7.4), doxorubicin was covalently tethered to the surface of MSNs, avoiding premature drug release when unnecessary. After exposure to acidic microenvironment, such as encountered in cancerous tissue or intracellular compartment endosome, the acid-labile citraconic bond was decomposed, releasing the active pharmaceutical ingredient, doxorubicin. The kinetic profiles of doxorubicin release have been studied under different pH conditions (ranging from 4 to 7.4), clearly indicating a pH-dependent controlled release behavior. MTT assay with human cervical cancer cells (HeLa) and confocal microscopy were used to study the anti-tumor activity and particle uptake behavior of Dox-MSN, respectively. A multitude of physicochemical analytical methods, including TEM, SEM, XRD, porosity analysis, IR spectroscopy, confirmed the successful fabrication of desired MSNs. These acidresponsive MSNs can be speculated to find wide ranging applications as nano-carriers in biomedical research, especially for targeted anticancer drug delivery.