Journal of Colloid and Interface Science 333 (2009) 812–815 Contents lists available at ScienceDirect Journal of Colloid and Interface Science www.elsevier.com/locate/jcis Short Communication Coating liposomes with yttrium basic carbonate: Making hybrid nanocapsules Martín G. Bellino a , Alberto E. Regazzoni a,b,∗ a Unidad de Actividad Química, Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica, Av. General Paz 1499, B1650KNA-San Martín, Argentina b Instituto Jorge A. Sabato, Universidad Nacional de San Martín, Av. General Paz 1499, B1650KNA-San Martín, Argentina article info abstract Article history: Received 4 December 2008 Accepted 16 February 2009 Available online 21 February 2009 Keywords: Nanocapsules Yttrium basic carbonate Liposomes Homogeneous alkalinization Urea Vesicles Template Core–shell Novel yttrium basic carbonate hybrid nanocapsules have been prepared using liposome templates. The method resorts to urea hydrolysis to increase the precipitation driving force of Y(OH)CO 3 ·xH 2 O homogeneously. The head groups at the outer vesicle layer act as adsorption sites for hydrolyzing Y(III) ions, thus assisting heterogeneous nucleation. The criteria behind the synthesis, as well as the potentialities of the advanced procedure, are stressed.  2009 Elsevier Inc. All rights reserved. 1. Introduction Inorganic hollow particles are the focus of increasing research. Due to their unique properties, these systems have promising applications in areas so disparate that span from catalysis to biomedicine [1–7]. In latter case, the inorganic shells are foreseen as carriers for drug or gene storage and/or controlled delivery [8]. As a rule, hollow inorganic particles are synthesized via calcina- tion of core–shell particles bearing polymeric cores [9]; selective leaching of sacrificial core templates, mainly, latex and SiO 2 , has also widespread use [10]. Encapsulation within these colloidal in- organic shells is restricted, however, to guest molecules that are able to retain their activity after the many preparation steps; viz., guests that remain stable during incorporation in the core matrix, and during core removal. Evidently, the possibilities are very lim- ited, especially if encapsulation of bioactive molecules is pursued. The simplest approach to encapsulation is hosting molecules within the water pool of phospholipid vesicles. Liposomes lack however the properties that are bestowed by inorganic shells. Li- posomes bearing inorganic shells are indeed rare. Silica-coated [11, 12] and calcium phosphate-coated [13,14] liposomes are the sole reports in the literature. These hybrid nanocapsules have been ob- tained following two somewhat different synthesis strategies; the former was prepared via hydrolysis-condensation of TEOS, whereas * Corresponding author at: Unidad de Actividad Química, Centro Atómico Consti- tuyentes, Comisión Nacional de Energía Atómica, Av. General Paz 1499, B1650KNA- San Martín, Argentina. Fax: +54 11 6772 7886. E-mail address: regazzon@cnea.gov.ar (A.E. Regazzoni). calcium phosphate-coated liposomes were synthesized by surface- precipitation from supersaturated solutions. Bearing in mind the very high reactivity of metal alcohox- ides, the instability of most liposomes in non-aqueous media, and the inherent difficulties in handling the supersaturation degree of aqueous solutions, the dearth of liposomes bearing shells of metal compounds is not surprising. Provided liposomes remain stable at the synthesis conditions, such shells could in principle be produced if the rates of nucleation and growth are adequately customized to induce heterogeneous nucleation and to avoid crystallization. Such a fine control of the degree of supersaturation can in fact be at- tained following the ideas behind the homogeneous precipitation approach [15]. To illustrate that liposome bearing shells of metal compounds can indeed be prepared when the above prerequisites are fulfilled, we report here the synthesis of hybrid nanocapsules of amorphous yttrium basic carbonate. The system was selected because yttrium compounds have promising applications, e.g., cancer radiotherapy [16], in vivo imaging [17], neuroprotection [18], etc. 2. Experimental Lipoid E80, a fat-free lecithin containing 80% phosphatidyl- choline (PDC), was from Lipoid AG, Germany. Y(NO 3 ) 3 ·6H 2 O and urea were analytical grade reagents. Stock solutions of the latter chemicals were made up using deionized water (conductivity less than 0.1 μS cm −1 ), and filtered through 200 nm pore size mem- branes. Thoroughly cleaned glassware was used in all cases. 0021-9797/$ – see front matter  2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jcis.2009.02.035