[12]aneN₃-Based Gemini-Type Amphiphiles with Two-Photon Absorption Properties for Enhanced Nonviral Gene Delivery and Bioimaging

Abstract

Although a plethora of nonviral gene vectors have been developed for potential gene therapy, imageable gemini surfactants with stimuli-responsiveness and high transfection efficiency are still scarce for gene delivery. Herein, three gemini amphiphiles (DEDPP-4/8/12) consisting of an aggregation-induced emission (AIE) central fluorophore: 5,6-diphenylpyrazine-2,3-diester (DEDPP), decorated with triazole-[12]­aneN3 as the hydrophilic moiety and alkyl chains of various lengths as the hydrophobic moiety, were designed and synthesized for trackable gene delivery via optical imaging. All three amphiphiles exhibited ultralow critical micelle concentrations (CMCs) (up to 3.40 × 10–6 M), prominent two-photon absorption properties, and solvatochromic fluorescence. Gel electrophoresis assays demonstrated that the migration of plasmid DNA was completely retarded after condensation with these gemini amphiphiles at low concentrations (up to 10 μM). In addition, the ester bond in these amphiphiles may facilitate vector degradation and DNA release, in response to esterase and the acidic environment inside cells. Upon self-assembly with DOPE to form liposomes, DEDPP-8/DOPE achieved the best transfection efficiency in four cell lines, and the transfection efficiency of DEDPP-8/DOPE in HeLa cell lines was 23.5-fold higher than that of Lipo2000, which is unusually high for small organic molecule-based nonviral vectors. Furthermore, excellent transfection efficiency of DEDPP-8/DOPE was obtained in the presence of serum, and the red fluorescence protein (RFP) gene was successfully transfected in zebrafish embryos. Both one- and two-photon fluorescence imaging clearly demonstrated the delivery process of plasmid DNA. This study demonstrated that gemini-type amphiphiles composed of a two-photon fluorophore core conjugated with triazole-[12]­aneN3 via an ester bond afforded an unprecedentedly high transfection efficiency with excellent biocompatibility, which may provide new insights for the design and development of multifunctional nonviral gene vectors for imageable gene delivery.

[12]aneN3-Conjugated AIEgens with two-photon imaging properties for synergistic gene/photodynamic therapy in vitro and in vivo

“…S5 (ESI †), the fluorescence intensity increases as the concentration increases, and these CMCs are 7.6 Â 10 À6 M, 6.3 Â 10 À6 M, 5.1 Â 10 À6 M, 1.0 Â 10 À6 M, 7.8 Â 10 À6 M and 1.9 Â 10 À6 M, respectively. Apparently, the CMCs of these compounds decreased with the increase of the bridged alkyl chain length, which is consistent with the reported literature, 29 which can be contributed to the enhancement of the hydrophobicity with the increase of the alkyl chain length.…”

“…However, the DNA condensation ability of the six compounds was greatly improved in the presence of DOPE, as those reported in the literature. [28][29][30]32 These liposomes completely retarded the DNA at 35, 15, 10, 15, 30 and 20 mM, respectively (Fig. 2(A)).…”

“…As for the absorption spectra (Fig. S1 and Table S1, ESI †), the maximum absorption wavelengths of the six compounds in different solvents varied in the range of 423-431 nm, 412-424 nm, 414-423 nm, 417-423 nm, 430-447 nm and 421-430 nm, respectively, which were caused by the p-p* transition, 29 and the variation is less than 12 nm. As shown in Fig.…”

“…This is the typical twisted intramolecular charge transfer (TICT) effect in these molecules, which is consistent with those in literature. [28][29][30] Scheme 2 Schematic synthetic route for TTC-L-M-1/2/3/4/5/6. To further explain the effect of solvatochromism of the target molecules TTC-L-M-1/2/3/4/5/6, the relationship between the Stokes shift (Dn) and the solvent polarity parameter (Df) was analyzed.…”

“…The [12]aneN 3 unit showed excellent DNA condensation properties through electrostatic neutralization for gene delivery and transfection. [28][29][30] The alkyl chains of various lengths are expected to regulate CMCs, the morphology of nanoparticles, endosomal escape, and transfection efficiency. Moreover, the TTC unit, an AIEgen with a two-photon absorption property, would generate ROS under laser irradiation.…”