179 research outputs found
Effect of Liposomal Encapsulation on the Chemical Exchange Properties of Diamagnetic CEST Agents
Exogenous chemical exchange saturation transfer (CEST)
contrast agents such as glucose or 2-deoxy-D-glucose (2-DG) have shown
high sensitivities and significant potential for monitoring glucose uptake in
tumors with MRI. Here, we show that liposome encapsulation of such agents
can be exploited to enhance the CEST signal by reducing the overall apparent
exchange rate. We have developed a concise analytical model to describe the
liposomal contrast dependence on several parameters such as pH,
temperature, irradiation amplitude, and intraliposomal water content. This
is the first study in which a model has been constructed to measure the
exchange properties of diamagnetic CEST agents encapsulated inside
liposomes. Experimentally measured exchange rates of glucose and 2-DG
in the liposomal system were found to be reduced due to the intermembrane
exchange between the intra- and extraliposomal compartments because of
restrictions in water transfer imposed by the lipid membrane. These new theoretical and experimental findings will benefit
applications of diamagnetic liposomes to image biological processes. In addition, combining this analytical model with
measurements of the CEST signal enhancement using liposomes as a model membrane system is an important new general
technique for studying membrane permeabilit
Drug delivery, biodistribution and anti-EGFR activity: theragnostic nanoparticles for simultaneous in vivo delivery of tyrosine kinase inhibitors and kinase activity biosensors
In vivo delivery of small molecule therapeutics to cancer cells, assessment of the selectivity of administration, and measuring the efficacity of the drug in question at the molecule level, are important ongoing challenges in developing new classes of cancer chemotherapeutics. One approach that has the potential to provide targeted delivery, tracking of biodistribution and readout of efficacy, is to use multimodal theragnostic nanoparticles to deliver the small molecule therapeutic. In this paper, we report the development of targeted theragnostic lipid/peptide/DNA lipopolyplexes. These simultaneously deliver an inhibitor of the EGFR tyrosine kinase, and plasmid DNA coding for a Crk-based biosensor, Picchu-X, which when expressed in the target cells can be used to quantify the inhibition of EGFR in vivo in a mouse colorectal cancer xenograft model. Reversible bioconjugation of a known analogue of the tyrosine kinase inhibitor Mo-IPQA to a cationic peptide, and co-formulation with peptides containing both EGFR-binding and cationic sequences, allowed for good levels of inhibitor encapsulation with targeted delivery to LIM1215 colon cancer cells. Furthermore, high levels of expression of the Picchu-X biosensor in the LIM1215 cells in vivo allowed us to demonstrate, using fluorescence lifetime microscopy (FLIM)-based biosensing, that EGFR activity can be successfully suppressed by the tyrosine kinase inhibitor, released from the lipopolyplexes. Finally, we measured the biodistribution of lipopolyplexes containing 125I-labelled inhibitors and were able to demonstrate that the lipopolyplexes gave significantly higher drug delivery to the tumors compared with free drug
Solution of the Bethe-Salpeter equation for pion-nucleon scattering
A relativistic description of pion-nucleon scattering based on the
four-dimensional Bethe-Salpeter equation is presented. The kernel of the
equation consists of s- and u-channel nucleon and delta pole diagrams, as well
as rho and sigma exchange in the t-channel. The Bethe-Salpeter equation is
solved by means of a Wick rotation, and good fits are obtained to the s- and
p-wave phase shifts up to 360 MeV pion laboratory energy. The coupling
constants determined by the fits are consistent with the commonly accepted
values in the literature.Comment: 34 pages, RevTeX; 7 figures. Several references added, a few typos
corrected. Accepted for publication in Physical Review
- …