Publications by authors named "Lucas J Tricoli"

3 Publications

  • Page 1 of 1

Direct observation of dynamic mechanical regulation of DNA condensation by environmental stimuli.

Angew Chem Int Ed Engl 2014 Sep 21;53(40):10631-5. Epub 2014 Aug 21.

Fischell Department of Bioengineering, University of Maryland, College Park, MD 20742 (USA).

Gene delivery is a promising way to treat hereditary diseases and cancer; however, there is little understanding of DNA:carrier complex mechanical properties, which may be critical for the protection and release of nucleic acids. We applied optical tweezers to directly measure single-molecule mechanical properties of DNA condensed using 19-mer poly-L-lysine (PLL) or branched histidine-lysine (HK) peptides. Force-extension profiles indicate that both carriers condense DNA actively, showing force plateaus during stretching and relaxation cycles. As the environment such as carrier concentration, pH, and the presence of zinc ions changes, DNA:HK complexes showed dynamically regulated mechanical properties at multiple force levels. The fundamental knowledge from this study can be applied to design a mechanically tailored complex which may enhance transfection efficiency by controlling the stability of the complex temporally and spatially.
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http://dx.doi.org/10.1002/anie.201403499DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5517097PMC
September 2014

Enhanced silencing and stabilization of siRNA polyplexes by histidine-mediated hydrogen bonds.

Biomaterials 2014 Jan 22;35(2):846-55. Epub 2013 Oct 22.

Department of Pathology, University of Maryland Baltimore, MSTF Building, 10 South Pine Street, Baltimore, MD 21201, United States; Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, MD 20742, United States. Electronic address:

Branched peptides containing histidines and lysines (HK) have been shown to be effective carriers for DNA and siRNA. We anticipate that elucidation of the binding mechanism of HK with siRNA will provide greater insight into the self-assembly and delivery of the HK:siRNA polyplex. Non-covalent bonds between histidine residues and nucleic acids may enhance the stability of siRNA polyplexes. We first compared the polyplex biophysical properties of a branched HK with those of branched asparagine-lysine peptide (NK). Consistent with siRNA silencing experiments, gel electrophoresis demonstrated that the HK siRNA polyplex maintained its integrity with prolonged incubation in serum, whereas siRNA in complex with NK was degraded in a time-dependent manner. Isothermal titration calorimetry of various peptides binding to siRNA at pH 7.3 showed that branched polylysine, interacted with siRNA was initially endothermic, whereas branched HK exhibited an exothermic reaction at initial binding. The exothermic interaction indicates formation of non-ionic bonds between histidines and siRNA; purely electrostatic interaction is entropy-driven and endothermic. To investigate the type of non-ionic bond, we studied the protonation state of imidazole rings of a selectively (15)N labeled branched HK by heteronuclear single quantum coherence NMR. The peak of Nδ1-H tautomers of imidazole shifted downfield (in the direction of deprotonation) by 0.5-1.0 ppm with addition of siRNA, providing direct evidence that histidines formed hydrogen bonds with siRNA at physiological pH. These results establish that histidine-rich peptides form hydrogen bonds with siRNA, thereby enhancing the stability and biological activity of the polyplex in vitro and in vivo.
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http://dx.doi.org/10.1016/j.biomaterials.2013.10.019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3920840PMC
January 2014

Surface-modified HK:siRNA nanoplexes with enhanced pharmacokinetics and tumor growth inhibition.

Biomacromolecules 2013 Mar 14;14(3):752-60. Epub 2013 Feb 14.

Department of Pathology, University of Maryland Baltimore, MSTF Building, 10 South Pine Street, Baltimore, MD 21201, USA.

We characterized in this study the pharmacokinetics and antitumor efficacy of histidine-lysine (HK):siRNA nanoplexes modified with PEG and a cyclic RGD (cRGD) ligand targeting αvβ3 and αvβ5 integrins. With noninvasive imaging, systemically administered surface-modified HK:siRNA nanoplexes showed nearly 4-fold greater blood levels, 40% higher accumulation in tumor tissue, and 60% lower luciferase activity than unmodified HK:siRNA nanoplexes. We then determined whether the surface-modified HK:siRNA nanoplex carrier was more effective in reducing MDA-MB-435 tumor growth with an siRNA targeting Raf-1. Repeated systemic administration of the selected surface modified HK:siRNA nanoplexes targeting Raf-1 showed 35% greater inhibition of tumor growth than unmodified HK:siRNA nanoplexes and 60% greater inhibition of tumor growth than untreated mice. The improved blood pharmacokinetic results and tumor localization observed with the integrin-targeting surface modification of HK:siRNA nanoplexes correlated with greater tumor growth inhibition. This investigation reveals that through control of targeting ligand surface display in association with a steric PEG layer, modified HK: siRNA nanoplexes show promise to advance RNAi therapeutics in oncology and potentially other critical diseases.
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http://dx.doi.org/10.1021/bm3018356DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3595641PMC
March 2013
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