Synthesis, characterization and biocompatibility of a multifunctional gold nanoparticle system for the delivery of single-stranded RNA to lymphocytes

The use of RNA macromolecules as therapeutic agents for HIV and other infectious diseases is promising but limited by suboptimal delivery to the target site. With HIV infection, this is particularly challenging since lymphocytes are particularly difficult to transfect. This paper describes an innovative strategy for the intracellular delivery of a novel single-stranded RNA (oligoribonucleotide) with putative anti-HIV activity. This strategy is based on a PEGylated gold nanoparticle scaffold covalently linked to the thiol-modified oligoribonucleotide via a cleavable N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP) linker molecule. The nanoparticle was then coated with a cationic polymer (polyethyleneimine) to facilitate cell entry and endosomal escape. A synthetic anti-CD4 cyclic targeting peptide was attached to the polyethyleneimine-coated nanoparticle via an SPDP linker molecule, in an attempt to enhance uptake and selectivity. Synthesis, characterization, SPDP and RNA loading, cytotoxicity and antiviral activity of the nanoparticle are described. Approximately 45 000 strands of RNA were taken up per lymphocyte. Uptake was limited by relatively inefficient loading ofRNAonto the gold nanoparticle surface (1 strand per 4.8 nm2 of nanoparticle surface area) and significant aggregation of the nanoparticle in physiological solutions. No antiviral activity was demonstrated, possibly due to insufficient intracytoplasmic delivery of the RNA.Keywords: Gold nanoparticle, polyethyleneimine, transfection, RNA deliver

6,7-Dimeth­oxy-3-meth­oxy­carbonyl-1-(2-meth­oxy­phen­yl)-3,4-dihydro­isoquinoline 2-oxide

In the title compound, C20H21NO6, an N-oxide-based organocatalyst, the N-containing six-membered ring adopts a twisted half-chair conformation. No hydrogen bonding or π–π stacking was found within the crystal structure

(S)-2-Benzyl-N-(2,6-diisopropyl­phen­yl)-1,2,3,4-tetra­hydro­isoquinoline-3-carboxamide

The asymmetric unit of the title compound, C29H34N2O, contains two mol­ecules in which the N-containing six-membered rings assume different conformations viz. half-chair and envelope. Inter­molecular N—H⋯O hydrogen bonding via the amide groups cross-link the mol­ecules in the crystal structure

Benzyl 5-hy­droxy-4-oxapenta­cyclo­[5.4.1.02,6.03,10.08,11]dodecane-3-carboxyl­ate

The title compound, C19H18O4, exhibits a long C—C bond [1.575 (2) Å] in the cage structure. In the crystal, pairs of O—H⋯O hydrogen bonds link the mol­ecules into centrosymmetric dimers. C—H⋯O inter­actions also occur

8-(Biphenyl-4-yl)-8-hydroxy­penta­cyclo­[5.4.0.02,6.03,10.05,9]undecan-11-one ethyl­ene ketal

The title compound, C25H24O3, synthesized as a potential chiral catalyst, exhibits a range of C—C bond lengths in the penta­cyclo­undecane cage between 1.5144 (18) and 1.5856 (16) Å. The two benzene rings are not planar with respect to each other, but rather are twisted at a torsion angle of 34.67 (17)°. The mol­ecule has an intra­molecular O—H⋯O inter­action and participates in two C—H⋯O inter­molecular inter­actions to form a one-dimensional chain

(1R,3S)-Methyl 2-benzyl-6,7-dimeth­oxy-1-phenyl-1,2,3,4-tetra­hydro­isoquinoline-3-carboxyl­ate

In the title compound, C26H27NO4, a precursor to novel chiral catalysts, the N-containing six-membered ring assumes a half-boat conformation. Various C—H⋯π interactions and intermolecular short contacts (C⋯H = 2.81–2.90 Å) link the mol­ecules together in the crystal structure

endo-11-(Dibenzyl­amino)­tetra­cyclo­[5.4.0.03,10.05,9]undecane-8-one

The structure of the title compound, C25H27NO, is a mono-ketone penta­cyclo­undecane (PCU) mol­ecule bearing a tertiary amine group. One of the methyl­ene groups in the PCU is disordered over two orientations with site-occupancy factors of 0.621 (7) and 0.379 (7)

(1S,3S)-Methyl 6,7-dimeth­oxy-1-phenyl-1,2,3,4-tetra­hydro­isoquinoline-3-carboxyl­ate

In the title compound, C19H21NO4, an organocatalyst with a tetra­hydro­isoquinoline backbone, the heterocyclic ring assumes a half-boat conformation. The dihedral angle between the aromatic rings is 82.93 (8)°. In the crystal, mol­ecules are linked via N—H⋯O and C—H⋯O hydrogen bonds, forming a layer parallel to (10)

tert-Butyl N-[(11-exo-benzyl­oxy­carbonyl-8-oxopenta­cyclo­[5.4.0.02,6.03,10.05,9]undecane-11-endo-yloxy)carbon­yl­methyl]carbamate

The structure of the title compound, C26H29NO7, at 173 K has an inter­molecular N—H⋯O hydrogen bond. This is one of the few examples where a mono-ketone penta­cyclo­undecane (PCU) mol­ecule exibits hydrogen bonding in the solid state. The dihedral angles of the amide and ester groups are normal and unaffected by the cage structure. A longer than normal C—C bond [1.571 (4) Å] was found within the cage structure

Ab initio Theoretical Investigation of a Formal Alkene-Enedione Intramolecular [2 + 2] Photocyclization

Irradiation of 1 with visible light results in intramolecular [2 + 2] photocyclization to afford the corresponding pentacyclic cage diketone, i.e. pentacyclo [5.4.0.02,6.03,10.05,9]undecane-8,11-dione (2). The mechanism of this reaction has been scrutinized by using ab initio theoretical methods. The results of these calculations provide new evidence which supports earlier suggestions that alkene-enedione photocyclizations may actually proceed via a diradical stepwise mechanism through the triplet excited state rather than as concerted [2 + 2] cycloadditions