A nano drug carrier based on sustainable and biocompatible nanocellulose was developed for use in prolonged drug releases. The grafting of beta-cyclodextrin (beta CD) on bacterial cellulose nanowhiskers (BCNC) using citric acid (CA) as a green linker was performed. This led to the formation of functionalized BCNC-grafted-beta CD (BCNC-g-beta CD). Broad-spectrum antibiotic Ciprofloxacin (CIP) and anticancer drugs Doxorubicin (DOX) and Paclitaxel (PTX) were used as model drugs. These model drugs were conjugated to BCNC-g-beta CD to form the drug-nanocarrier systems (BCNC-g-beta CD-drug). The change in the nanowhiskers' surface chemistry, morphology, and crystallinity was characterized by FTIR, solid-state C-13 NMR, scanning electron microscopy (SEM), atomic force microscopy (AFM), and x-ray diffraction (XRD). The functionalized nanowhiskers showed a significant increase in the drug payloads, which ranged from 495 +/- 4-810 +/- 7 mu g/mg, along with a radical improvement in the drug release profiles. For all of the developed drug-conjugated nanocarriers, the initial burst releases were reduced effectively. The observed drug releases showed a sustained and controlled manner, with cumulative releases of 75-90 % over 5-5.5 days. Nevertheless, an improved drug release performance was observed in the acidic pH of 6.4 that mimicked extracellular tumor cells. In vitro drug release data were fitted zero-order kinetic model with drug release constants (K-0) of 0.68, 0.74, and 0.79 mu g drug/h (at pH 6.4 and 37 degrees C) for BCNC-g-beta CD-CIP, BCNC-g-beta CD-DOX, and BCNC-g-beta CD-PTX nanosystems, respectively. The observed higher payloads along with the slow releases of drugs from the developed nanocarrier suggests its promising potential for reducing the frequent daily dosing and minimizing systemic toxicity of loaded drugs.