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Passive and pH-gradient loading of doxycycline into nanoliposomes using modified freeze-drying of a monophase solution method for enhanced antibacterial activity

Pouria Savadi, Farzaneh Lotfipour, Nigel A. J. McMillan, Nastaran Hashemzadeh, and Somayeh Hallaj-Nezhadi

Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran



Received: 22 August 2021  Accepted: 22 December 2021


Antibiotic resistance is one of the most serious health challenges worldwide. In this study, nanoliposomal encapsulations of doxycycline with enhanced antibacterial effects were prepared using the modified freeze-drying of a monophase solution and two loading techniques (passive and pH-gradient) simultaneously. Different liposomes were prepared and characterized in terms of size, zeta-potential, polydispersity-index, morphology, ATR-FTIR, Powder X-ray Diffraction, and encapsulation-efficiency (EE). MICs and time–kill-experiments were performed according to CLSI guidelines. The liposomes were nano-sized and spherical in shape. The EE of the selected formulation was 37.4 ± 5.8%. The MICs were two-fold lower than those of equivalent free drugs. Nanoliposomes at 4 × MIC revealed a rapid killing of Staphylococcus epidermidis by achieving complete bacterial death at 8 h versus 16 h for the free drug. Taking five aspects (homogeneous and nano-sized liposomes, sterilization not necessary, suitable EE, and antibacterial effects) into consideration, our modified preparation method seems promising and may be used to overcome bacterial resistance.

Graphical abstract

Nanoliposomal doxycycline was made via modified freeze-drying of a monophase solution. Passive and pH-gradient drug-loading resulted in suitable encapsulation efficiencies. Sterile and homogeneous nanoliposomes with good antibacterial effects were obtained. The minimum inhibitory concentrations decreased two-fold. This technique may be used to overcome bacterial resistance to doxycycline.

Keywords: Nanoliposomes; Doxycycline; Freeze-drying of a monophase solution; pH-gradient; Staphylococcus aureus; Staphylococcus epidermidis

Full paper is available at

DOI: 10.1007/s11696-021-02036-5


Chemical Papers 76 (5) 3097–3108 (2022)

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