Efficient protection and transfection of small interfering RNA by cationic shell-crosslinked knedel-like nanoparticles

In vivo fate tracking of degradable nanoparticles for lung gene transfer using PET and Ĉerenkov imaging

Nanoparticles (NPs) play expanding roles in biomedical applications including imaging and therapy, however, their long-term fate and clearance profiles have yet to be fully characterized in vivo. NP delivery via the airway is particularly challenging, as the clearance may be inefficient and lung immune responses complex. Thus, specific material design is required for cargo delivery and quantitative, noninvasive methods are needed to characterize NP pharmacokinetics. Here, biocompatible poly(acrylamidoethylamine)-b-poly(dl-lactide) block copolymer-based degradable, cationic, shell-cross-linked knedel-like NPs (Dg-cSCKs) were employed to transfect plasmid DNA. Radioactive and optical beacons were attached to monitor biodistribution and imaging. The preferential release of cargo in acidic conditions provided enhanced transfection efficiency compared to non-degradable counterparts. In vivo gene transfer to the lung was correlated with NP pharmacokinetics by radiolabeling Dg-cSCKs and performing quantitative biodistribution with parallel positron emission tomography and Čerenkov imaging. Quantitation of imaging over 14 days corresponded with the pharmacokinetics of NP movement from the lung to gastrointestinal and renal routes, consistent with predicted degradation and excretion. This ability to noninvasively and accurately track NP fate highlights the advantage of incorporating multifunctionality into particle design.

Repetitive centromeric satellite RNA is essential for kinetochore formation and cell division

SAT III RNA binds to the kinetochore component CENP-C and is required for correct assembly and function of the kinetochore at centromeres.

Chromosome segregation requires centromeres on every sister chromatid to correctly form and attach the microtubule spindle during cell division. Even though centromeres are essential for genome stability, the underlying centromeric DNA is highly variable in sequence and evolves quickly. Epigenetic mechanisms are therefore thought to regulate centromeres. Here, we show that the 359-bp repeat satellite III (SAT III), which spans megabases on the X chromosome of Drosophila melanogaster, produces a long noncoding RNA that localizes to centromeric regions of all major chromosomes. Depletion of SAT III RNA causes mitotic defects, not only of the sex chromosome but also in trans of all autosomes. We furthermore find that SAT III RNA binds to the kinetochore component CENP-C, and is required for correct localization of the centromere-defining proteins CENP-A and CENP-C, as well as outer kinetochore proteins. In conclusion, our data reveal that SAT III RNA is an integral part of centromere identity, adding RNA to the complex epigenetic mark at centromeres in flies.

Polyphosphoester-based cationic nanoparticles serendipitously release integral biologically-active components to serve as novel degradable inducible nitric oxide synthase inhibitors

A degradable polyphosphoester (PPE)-based cationic nanoparticle (cSCK), which is integrated constructed as a novel degradable drug device, demonstrates surprisingly efficient inhibition of inducible nitric oxide synthase (iNOS) transcription, and eventually inhibits nitric oxide (NO) over-production, without loading of any specific therapeutic drugs. This system may serve as a promising anti-inflammatory agent toward the treatment of acute lung injury.

Imaging mRNA expression levels in living cells with PNA·DNA binary FRET probes delivered by cationic shell-crosslinked nanoparticles

Optical imaging of gene expression through the use of fluorescent antisense probes targeted to the mRNA has been an area of great interest. The main obstacles to developing highly sensitive antisense fluorescent imaging agents have been the inefficient intracellular delivery of the probes and high background signal from unbound probes. Binary antisense probes have shown great promise as mRNA imaging agents because a signal can only occur if both probes are bound simultaneously to the mRNA target site. Selecting an accessible binding site is made difficult by RNA folding and protein binding in vivo and the need to bind two probes. Even more problematic, has been a lack of methods for efficient cytoplasmic delivery of the probes that would be suitable for eventual applications in vivo in animals. Herein we report the imaging of iNOS mRNA expression in live mouse macrophage cells with PNA·DNA binary FRET probes delivered by a cationic shell crosslinked knedel-like nanoparticle (cSCK). We first demonstrate that FRET can be observed on in vitro transcribed mRNA with both the PNA probes and the PNA·DNA hybrid probes. We then demonstrate that the FRET signal can be observed in live cells when the hybrid probes are transfected with the cSCK, and that the strength of the FRET signal is sequence specific and depends on the mRNA expression level.