3 research outputs found
Pyrrolidinyl Peptide Nucleic Acid Homologues: Effect of Ring Size on Hybridization Properties
The effect of ring size of four- to six-membered cyclic β-amino acid on the hybridization properties of pyrrolidinyl peptide nucleic acid with an alternating α/β peptide backbone is reported. The cyclobutane derivatives (acbcPNA) show the highest <i>T</i><sub>m</sub> and excellent specificity with cDNA and RNA
Hydrophilic and Cell-Penetrable Pyrrolidinyl Peptide Nucleic Acid via Post-synthetic Modification with Hydrophilic Side Chains
Peptide nucleic acid (PNA) is a nucleic acid mimic in which the
deoxyribose–phosphate was replaced by a peptide-like backbone.
The absence of negative charge in the PNA backbone leads to several
unique behaviors including a stronger binding and salt independency
of the PNA–DNA duplex stability. However, PNA possesses poor
aqueous solubility and cannot directly penetrate cell membranes. These
are major obstacles that limit in vivo applications of PNA. In previous
strategies, the PNA can be conjugated to macromolecular carriers or
modified with positively charged side chains such as guanidinium groups
to improve the aqueous solubility and cell permeability. In general,
a preformed modified PNA monomer was required. In this study, a new
approach for post-synthetic modification of PNA backbone with one
or more hydrophilic groups was proposed. The PNA used in this study
was the conformationally constrained pyrrolidinyl PNA with prolyl-2-aminocyclopentanecarboxylic
acid dipeptide backbone (acpcPNA) that shows several advantages over
the conventional PNA. The aldehyde modifiers carrying different linkers
(alkylene and oligo(ethylene glycol)) and end groups (−OH,
−NH<sub>2</sub>, and guanidinium) were synthesized and attached
to the backbone of modified acpcPNA by reductive alkylation. The hybrids
between the modified acpcPNAs and DNA exhibited comparable or superior
thermal stability with base-pairing specificity similar to those of
unmodified acpcPNA. Moreover, the modified apcPNAs also showed the
improvement of aqueous solubility (10–20 folds compared to
unmodified PNA) and readily penetrate cell membranes without requiring
any special delivery agents. This study not only demonstrates the
practicality of the proposed post-synthetic modification approach
for PNA modification, which could be readily applied to other systems,
but also opens up opportunities for using pyrrolidinyl PNA in various
applications such as intracellular RNA sensing, specific gene detection,
and antisense and antigene therapy
Bringing Macromolecules into Cells and Evading Endosomes by Oxidized Carbon Nanoparticles
A great challenge exists in finding
safe, simple, and effective delivery strategies to bring matters across
cell membrane. Popular methods such as viral vectors, positively charged
particles and cell penetrating peptides possess some of the following
drawbacks: safety issues, lysosome trapping, limited loading capacity,
and toxicity, whereas electroporation produces severe damages on both
cargoes and cells. Here, we show that a serendipitously discovered,
relatively nontoxic, water dispersible, stable, negatively charged,
oxidized carbon nanoparticle, prepared from graphite, could deliver
macromolecules into cells, without getting trapped in a lysosome.
The ability of the particles to induce transient pores on lipid bilayer
membranes of cell-sized liposomes was demonstrated. Delivering 12-base-long
pyrrolidinyl peptide nucleic acids with d-prolyl-(1<i>S</i>,2<i>S</i>)-2-aminocyclopentanecarboxylic acid
backbone (acpcPNA) complementary to the antisense strand of the NF-κB
binding site in the promoter region of the <i>Il6</i> gene
into the macrophage cell line, RAW 264.7, by our particles resulted
in an obvious accumulation of the acpcPNAs in the nucleus and decreased <i>Il6</i> mRNA and IL-6 protein levels upon stimulation. We anticipate
this work to be a starting point in a new drug delivery strategy,
which involves the nanoparticle that can induce a transient pore on
the lipid bilayer membrane