Design of bio-nanosystems for oral delivery of functional compounds

Nanotechnology has been referred to as one of the most interesting topics in food technology due to the potentialities of its use by food industry. This calls for studying the behavior of nanosystems as carriers of biological and functional compounds aiming at their utilization for delivery, controlled release and protection of such compounds during food processing and oral ingestion. This review highlights the principles of design and production of bio-nanosystems for oral delivery and their behavior within the human gastrointestinal (GI) tract, while providing an insight into the application of reverse engineering approach to the design of those bio-nanosystems. Nanocapsules, nanohydrogels, lipid-based and multilayer nanosystems are discussed (in terms of their main ingredients, production techniques, predominant forces and properties) and some examples of possible food applications are given. Phenomena occurring in in vitro digestion models are presented, mainly using examples related to the utilization of lipid-based nanosystems and their physicochemical behavior throughout the GI tract. Furthermore, it is shown how a reverse engineering approach, through two main steps, can be used to design bio-nanosystems for food applications, and finally a last section is presented to discuss future trends and consumer perception on food nanotechnology.Miguel A. Cerqueira, Ana C. Pinheiro, Helder D. Silva, Philippe E. Ramos, Ana I. Bourbon, Oscar L. Ramos (SFRH/BPD/72753/2010, SFRH/BD/48120/2008, SFRH/BD/81288/2011, SFRH/BD/80800/2011, SFRH/BD/73178/2010 and SFRH/BPD/80766/2011, respectively) are the recipients of a fellowship from the Fundacao para a Ciencia e Tecnologia (FCT, POPH-QREN and FSE Portugal). Maria L. Flores-Lopez thanks Mexican Science and Technology Council (CONACYT, Mexico) for PhD fellowship support (CONACYT Grant number: 215499/310847). The support of EU Cost Actions FA0904 and FA1001 is gratefully acknowledged

Competing quantum spin liquids, gauge fluctuations, and anisotropic interactions in a breathing pyrochlore lattice

We use the projective symmetry group analysis to classify the quantum spin liquids on the S=1/2 pyrochlore magnet with a breathing anisotropy. We find 40 Z2 spin liquids and 16 U(1) spin liquids that respect the F4¯3m space group and the time reversal symmetry. As an application, we consider the antiferromagnetic Heisenberg model, which is proposed to be the dominant interaction in the candidate material Ba3Yb2Zn5O11. Focusing on the U(1) spin liquid Ansätze, we find that only two of them are physical when restricted to this model. We present an analytical solution to the parton mean field theory for each of these two U(1) spin liquids. It is revealed that one of them has gapless, while the other one has gapped, spinon excitations. The two U(1) spin liquids are equal in energy regardless of the degree of breathing anisotropy, and they can be differentiated by the low-temperature heat capacity contribution from the quadratically dispersing gapless spinons. We further show that the latter is unaffected by fluctuations of the U(1) gauge field within the random phase approximation. Finally, we demonstrate that a small Dzyaloshinskii-Moriya interaction lifts the degeneracy between the two U(1) spin liquids, and it eventually causes the lattice to decouple into independent tetrahedra at strong coupling. While current model parameters for Ba3Yb2Zn5O11 place it indeed in the decoupled regime, other candidate materials may be synthesized in the near future that realize the spin liquid states discussed in our work