Construction of Polycation‐Based Non‐Viral DNA Nanoparticles and Polyanion Multilayers via Layer‐by‐Layer Self‐Assembly

Summary: The multilayers of polycation‐based non‐viral DNA nanoparticles and biodegradable poly(L ‐glutamic acid) (PGA) were constructed by a layer‐by‐layer (LbL) technique. Poly(ethyleneimine) (PEI) was used to condense DNA to develop non‐viral DNA nanoparticles. AFM, UV‐visible spectrometry, and TEM measurements revealed that the PEI‐DNA nanoparticles were successfully incorporated into the multilayers. The well‐structured, easily processed multilayers with the non‐viral DNA nanoparticles may provide a novel approach to precisely control the delivery of DNA, which may have great potential for gene therapy applications in tissue engineering, medical implants, etc.

A TEM image of the cross section of a (PGA/PEI‐DNA nanoparticle)₂₀ multilayer.     

Oligodeoxynucleotide Duplexes Containing (5′S)‐5′‐C‐Alkyl‐Modified 2′‐Deoxynucleosides: Can an Alkyl Zipper across the DNA Minor‐Groove Enhance Duplex Stability?

A series of oligonucleotides containing (5′S)‐5′‐C‐butyl‐ and (5′S)‐5′‐C‐isopentyl‐substituted 2′‐deoxyribonucleosides were designed, prepared, and characterized with the intention to explore alkyl‐zipper formation between opposing alkyl chains across the minor groove of oligonucleotide duplexes as a means to modulate DNA‐duplex stability. From four possible arrangements of the alkyl groups that differ in the density of packing of the alkyl chains across the minor groove, three (duplex types I – III , Fig. 2) could experimentally be realized and their duplex‐forming properties analyzed by UV‐melting curves, CD spectroscopy, and isothermal titration calorimetry (ITC), as well as by molecular modeling. The results show that all arrangements of alkyl residues within the minor groove of DNA are thermally destabilizing by 1.5–3°/modification in T_m. We found that, within the proposed duplexes with more loosely packed alkyl groups (type‐ III duplexes), accommodation of alkyl residues without extended distorsion of the helical parameters of B‐DNA is possible but does not lead to higher thermodynamic stability. The more densely packed and more unevenly distributed arrangement (type‐ II duplexes) seems to suffer from ecliptic positioning of opposite alkyl groups, which might account for a systematic negative contribution to stability due to steric interactions. The decreased stability in the type‐ III duplexes described here may be due either to missing hydrophobic interactions of the alkyl groups (not bulky enough to make close contacts), or to an overcompensation of favorable alkyl‐zipper formation presumably by loss of structured H₂O in the minor groove.     

Fabrication of oligo‐glycerol based hydrolase responsive amphiphilic nanocarriers

Herein, we report on the synthesis of a new class of novel non‐ionic amphiphiles using triglycerol as a core, which is further functionalized with hydrophilic units poly(ethylene glycol) monomethyl ether (M_n: 350 and 550) and a pair of hydrophobic alkyl chains (C₁₈ or C₁₅) via chemo‐enzymatic approach. Fluorescence measurements and dynamic light scattering studies showed that all of the synthesized amphiphilic systems spontaneously self‐ assemble in aqueous solution, which is further confirmed by the transmission electron microscopy. Encapsulation of hydrophobic moieties like Nile red and nimodipine was studied using ultraviolet‐visible (UV‐vis) and fluorescence spectrometer techniques. A cytotoxicity study of the amphiphiles using A549, HeLa, and MCF7 cell, which showed that all of the synthesized nanocarriers are well tolerated at the concentrations studied. The release profile of encapsulated Nile red in synthesized amphiphilic system was studied in the presence of the immobilized enzyme (Novozym 435).     

Photoinduced and thermally induced cationic polymerizations using S,S‐dialkyl‐S‐(3,5‐dimethylhydroxyphenyl)sulfonium salts

A study of the photoinitiated and thermally initiated cationic polymerizations of several monomer systems with S,S‐dialkyl‐S‐(3,5‐dimethylhydroxyphenyl)sulfonium salt (HPS) photoinitiators bearing different lengths of alkyl chains on the positively charged sulfur atom has been conducted. HPS photoinitiators are capable of photoinitiating the cationic polymerization of a wide variety of epoxy and vinyl ether monomers directly on irradiation with short‐wavelength UV light. Aryl ketone photosensitizers are effective in extending the spectral response of these photoinitiators into the long‐wavelength UV region. Kinetic studies with real‐time infrared spectroscopy show that HPS photoinitiators exhibit good efficiency in the polymerization of epoxide and vinyl ether monomers. Comparative studies also demonstrate that S,S‐dimethyl‐S‐(3,5‐dimethyl‐2‐hydroxyphenyl)sulfonium salts are more active photoinitiators than their isomeric S,S‐dimethyl‐S‐(3,5‐dimethyl‐4‐hydroxyphenyl)sulfonium salt counterparts. Both types of HPS photoinitiators display reversible photolysis as a result of facile termination reactions that take place between the growing chains ends with the photogenerated sulfur ylides. Preliminary studies have shown that HPS photoinitiators can also be employed as thermal initiators for the cationic ring‐opening polymerization of epoxides at moderate temperatures. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2570–2587, 2003     

Visible‐Light‐Induced Morphological Changes of Giant Vesicles by Photoisomerization of a Ruthenium Aqua Complex

Visible‐ and red‐light responsive vesicles were prepared by incorporating a ruthenium aqua complex having two alkyl chains on tridentate and asymmetrical bidentate ligands (proximal‐ 2 : [Ru(C₁₀tpy)(C₁₀pyqu)OH₂]²⁺, C₁₀tpy=4′‐decyloxy‐2,2′;6′,2“‐terpyridine, C₁₀pyqu=2‐[2′‐(6′‐decyloxy)‐pyridyl]quinoline). The ruthenium complex of proximal‐ 2 with closed alkyl chain geometry and a cylinder‐like molecular shape exhibited photoisomerization to distal‐ 2 with an open alkyl chain geometry and a cone‐like shape, both in an aqueous solution and in vesicle dispersions. We observed that light irradiation of giant vesicles containing proximal‐ 2 induced diverse morphological changes.     

Synthesis and self‐assembly of rod‐coil molecules with n‐shaped rod building block

The rod‐coil molecules with n‐shaped rod building block, consisting of an anthracene unit and two biphenyl groups linked together with acetylenyl bonds at the 1,8‐position of anthracene as a rigid rod segment, and the alkyl or alkyloxy chains with various length (i.e., methoxy‐ ( 1 ), octyl‐ ( 2 ), hexadecyl‐ ( 3 )) at the 10‐position of anthracene and poly(ethylene oxide) with the number of repeating units of 7 connected with biphenyl as coil segments were synthesized. The molecular structures were characterized by ¹H NMR and MALDI‐TOF mass spectroscopy. The self‐assembling behavior of new type of molecules 1–3 was investigated by means of DSC, POM, and SAXS at the bulk state. These molecules with a n‐shaped rod building block segment self‐assemble into supramolecular structures through the combination of π–π stacking of rigid rod building blocks and microphase separation of the rod and coil blocks. SAXS studies reveal that molecules 1 and 2 show hexagonal columnar and rectangular columnar structures in the liquid crystalline phase, respectively; meanwhile, molecules 1–3 self‐organize into lamellar structures in the crystalline state. In addition, self‐assembling studies of molecules 1–3 by DLS and TEM indicated that these molecules self‐assemble into elongated nanofibers in aqueous medium. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1415–1422, 2010     

3,6‐linked 9‐alkyl‐9H‐carbazole main‐chain polymers: Preparation and properties

An investigation into the preparation of poly(9‐alkyl‐9H‐carbazole‐3,6‐diyl)s with palladium catalyzed cross‐coupling reactions of 3‐halo‐6‐halomagnesio‐9‐alkyl‐9H‐carbazoles, generated in situ from their corresponding 3,6‐diiodo‐ and 3,6‐dibromo‐derivatives was undertaken. Monomers with a range of alkyl group substituents with different steric requirements were investigated and their effects on the polymerization were studied. The effects of the nature of halogen substituents on the polymerization reaction were also investigated. Structural analysis of the polymers revealed exclusive 3,6‐linkage between consecutive carbazole repeat units on the polymer chains. The physical properties of these polymers were investigated with spectroscopic, thermal gravimetric analysis, and electrochemical studies. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6041–6051, 2004     

Light‐ and Solvent‐Controlled Self‐Assembly Behavior of Spiropyran–Polyoxometalate–Alkyl Hybrid Molecules

A molecular photochromic spiropyran–polyoxometalate–alkyl organic–inorganic hybrid has been synthesized and fully characterized. The reversible switching of the hydrophobic spiropyran fragment to the hydrophilic merocyanine one can be easily achieved under light irradiation at different wavelengths. This switch changes the amphiphilic feature of the hybrid, leading to a light‐controlled self‐assembly behavior in solution. It has been shown that the hybrid can reversibly self‐assemble into vesicles in polar solvents and irreversibly into reverse vesicles in non‐polar solvents. The sizes of the vesicles and the reverse vesicles are both tunable by the polarity of the solvent, with the hydrophobic interactions being the main driving force.     

Amine containing cationic methacrylate copolymers as efficient gene delivery vehicles to retinal epithelial cells

Non‐viral gene delivery vectors have emerged as potential alternatives in the field of gene therapy by replacing the biological viral vectors. DNA–cationic polymer complexes are one of the most promising systems to target many inborn or acquired diseases without the utilization of conventional drugs. Despite the excellent binding efficiency of cationic polymers, the gene transfection seems limited to date. In this work, a series of ammonium‐based block‐copolymers with different alkyl side chains (ethyl, butyl, and hexyl) and functionality (alcohol, amine, and alkyl) have been prepared to evaluate their capacity to deliver genetic material. First, different ionic liquid monomers with different pendent functional groups were prepared and characterized. Then, polyplexes elaborated with different polymers at several polymer DNA ratios (w/w) were characterized in terms of size, zeta potential, and DNA binding, release, and protection capacity. Finally, the transfection efficiency and cell viability was evaluated in ARPE19 cells. We found that only the systems containing the amine pendent group were able to transfect ARPE19 cell and, that this amine containing polymer was less cytotoxic even at high polymer/DNA ratios (30:1). In conclusion, our studies suggested that the proper selection of the pendent group substantially impacts overall transfection efficiency of cationic polymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 280–287     

Synthesis of 2,3‐dihydro‐1,3‐thiazin‐4(1H)‐ ones and their remarkably facile recyclization to 2,3‐dihydropyrimidin‐4(1H)‐ones

Functionalized 2,3‐dihydro‐1,3‐thiazin‐4(1H)‐one derivatives have been synthesized by cyclocondensation of 3‐alkyl(aryl)amino‐2‐cyano‐3‐mercaptoacrylamides with aldehydes and ketones under acidic catalysis. 6‐Alkyl(aryl)amino‐5‐cyano‐2,3‐dihy‐ dro‐1,3‐thiazin‐4(1H)‐ones, when treated with a dilute solution of potassium hydroxide, are converted into the potassium salts of isomeric compounds, 1‐alkyl‐ (aryl)‐5‐cyano‐6‐mercapto‐2,3‐dihydropyrimidin‐ 4(1H)‐ones. Alkylation of the latter with dimethyl sulfate in situ furnishes 1‐alkyl(aryl)‐6‐alkylthio‐5‐ cyano‐2,3‐dihydropyrimidin‐4(1H)‐ones, whereas boiling them in ethanol with an excess of hydrochloric acid leads to starting 2,3‐dihydro‐1,3‐thiazin‐4(1H)‐ones. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:426–436, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20129     

Amphiphilic PEG/alkyl‐grafted comb polylactides

Amphiphilic polylactides (PLAs) with well‐defined architectures were synthesized by ring‐opening polymerization of AB monomers (glycolides) substituted with both a long chain alkyl group and a triethylene glycol segment terminated in either a methyl or benzyl group. The resulting amphiphilic PLAs had number average molecular weights >100,000 g/mol. DSC analysis revealed a first‐order phase transition at ～ 20 °C, reflecting the crystalline nature of the linear alkyl side chains. Polymeric micelles were prepared by the solvent displacement method in water. Dynamic light scattering measurements support formation of a mixture of 20‐nm‐diameter unimolecular micelles and 60‐nm particles comprised of an estimated 25 polymer molecules. UV–vis characterization of micelles formed from acetone–water solutions containing azobenzene confirmed encapsulation of the hydrophobic dye, suggesting their potential as new amphiphilic PLAs as drug delivery vehicles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5227–5236, 2007     

Synthesis,characterization, and large two‐photon absorption cross‐sections of solid red‐emitting 1,4‐diketo‐3,6‐diphenylpyrrolo [3,4‐c]pyrrole/3,6‐carbazole/terfluorene copolymers

The synthesis, one‐ and two‐photon absorption (TPA) and emission properties of three novel 1,4‐diketo‐3,6‐diphenylpyrrolo[3,4‐c]pyrrole (DPP)/3,6‐carbazole (Cz)/terfluorene (TF) copolymers are reported. The molar ratios of DPP versus TF are 15:85 ( TCP15 ), 25:75 ( TCP25 ), and 50:50 ( TCP50 ) under Cz:(TF + DPP) = 1. Two distinguished one‐photon absorption and emission bands observed in solutions imply that the electronic states of Cz–DPP–Cz and Cz–TF–Cz are not well mixed and the energy transfer from TF segments to DPP units is incomplete. However, in film states, all three copolymers are monochromatic red emitting with the peak wavelengths at 617, 621, and 631 nm for TCP15 , TCP25 , and TCP50 , respectively, indicating that the interchain interactions also have played an important role in the energy transfer. In two‐photon measurement, the copolymer solutions still exhibit two distinguished emission bands but the relative intensities at short‐wavelength region are obviously decreased, implying that Cz–TF–Cz segment is high one‐photon active but low TPA active, whereas Cz–DPP–Cz unit is low one‐photon active but high TPA active. All the copolymers show large δ over the range of measured wavelengths and the δ values of TCP15 , TCP25 , and TCP50 increase with DPP contents and are up to 530, 770, and 850 GM per repeating unit, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

A Tailor‐Made Specific Anion‐Binding Motif in the Side Chain Transforms a Tetrapeptide into an Efficient Vector for Gene Delivery

Arginine‐rich cell‐penetrating peptides are widely utilized as vectors for gene delivery. However, their transfection efficacy still needs to be optimized. To accomplish this, guanidinocarbonylpyrrole groups, which are tailor‐made anion binding sites, were introduced into the side chains of tetralysine to obtain the peptide analogue 1 . In contrast to the common strategy of adding a lipophilic tail to peptide vectors, this novel method most likely enhances transfection efficacy through more specific interactions between the binding motifs and DNA or the cell membrane. Tetrapeptide analogue 1 is thus the smallest peptidic transfection vector that has been reported to date. The transfection efficacy of 1 , which on average has less than two positive charges under physiological conditions, is even better than that of polyethylenimine (PEI). Furthermore, 1 exhibits only negligible cytotoxicity, which makes it an interesting candidate for further development.     

Multistimuli responsive micelles based on well‐defined amphiphilic comb poly(ether amine) (acPEA)

A series of well‐defined amphiphilic comb poly (ether amine)s (acPEAs) were successfully synthesized through nucleophilic addition/ring‐opening reaction of commercial available poly(propylene glycol) (PPO) diglycidyl ether and Jeffamine L100, followed by esterification of hydroxyl groups in backbone by alkyl carboxylic acid with different chain length. acPEAs are comprised of hydrophilic short PEO chains and hydrophobic alkyl chains as comb chains, which are grafted on PPO backbone alternately to form well‐defined structure. With the very low critical micelle concentration (CMC) of around 3.0 × 10^?3 g/L, the obtained acPEAs can self‐assemble into stable nanomicelles, whose aggregation is responsive to temperature, pH, and ionic strength with tunable cloud point (CP). The CP of acPEAs' aqueous solution increases with the decrease of the length of graft alkyl chains, the decrease of pH value, and the decrease of ionic strength. A transition behavior in the responsive aggregation of micelles formed by acPEA8 and acPEA10 in aqueous solution, especially at low pH value (<7.0), was observed, which was also revealed by DLS results. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3468–3475, 2010     

Synthesis and structure‐activity relationship of several aromatic ketone‐based two‐photon initiators

Several novel aromatic ketone‐based two‐photon initiators containing triple bonds and dialkylamino groups were synthesized and the structure‐activity relationships were evaluated. Branched alkyl chains were used at the terminal donor groups to improve the solubility in the multifunctional monomers. Because of the long conjugation length and good coplanarity, the evaluated initiators showed large two‐photon cross section values, while their fluorescence lifetimes and quantum yields strongly depend on the solvent polarity. All novel initiators exhibited high activity in terms of two‐photon‐induced microfabrication. This is especially true for fluorenone‐based derivatives, which displayed much broader processing windows than well‐known highly active initiators from the literature and commercially available initiators. While the new photoinitiators gave high reactivity in two‐photon‐induced photopolymerization at concentration as low as 0.1% wt, these compounds are surprisingly stable under one photon condition and nearly no photo initiation activity was found in classical photo DSC experiment. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Polymer Structure‐Guided Self‐Assisted Preparation of Poly(ester‐thioether)‐Based Hollow Porous Microspheres and Hierarchically Interconnected Microcages for Drug Release

Porous polymer microspheres (PPMs) have been widely applied in various biomedical fields. Herein, the self‐assisted preparation of poly(ester‐thioether)‐based porous microspheres and hierarchical microcages, whose pore sizes can be controlled by varying the polymer structures, is reported. Poly(ester‐thioether)s with alkyl side chains (carbon atom numbers were 2, 4, and 8) can generate hollow porous microspheres; the longer alkyl chain length, the larger pore size of microspheres. The allyl‐modified poly(ester‐thioether) (PHBDT‐g‐C₃) can form highly open, hierarchically interconnected microcages. A formation mechanism of these PPMs is proposed; the hydrophobic side chains‐mediated stabilization of oil droplets dictate the droplet aggregation and following solvent evaporation, which is the key to the formation of PPMs. The hierarchically interconnected microcages of PHBDT‐g‐C₃ are due to the partially crosslinking of polymers. Pore sizes of PPMs can be further tuned by a simple mixing strategy of poly(ester‐thioether)s with different pore‐forming abilities. The potential application of these PPMs as H₂O₂‐responsive vehicles for delivery of hydrophobic (Nile Red) and hydrophilic (doxorubicin hydrochloride) cargos is also investigated. The microspheres with larger pore sizes show faster in vitro drug release. The poly(ester‐thioether)‐based polymer microspheres can open a new avenue for the design of PPMs and provide a H₂O₂‐responsive drug delivery platform.     

Self‐Generation of Surface Roughness by Low‐Surface‐Energy Alkyl Chains for Highly Stable Superhydrophobic/Superoleophilic MOFs with Multiple Functionalities

We transformed the hydrophilic metal–organic framework (MOF) UiO‐67 into hydrophobic UiO‐67‐R s (R=alkyl) by introducing alkyl chains into organic linkers, which not only protected hydrophilic Zr₆O₈ clusters to make the MOF interspace superoleophilic, but also led to a rough crystal surface beneficial for superhydrophobicity. The UiO‐67‐R s displayed high acid, base, and water stability, and long alkyl chains offered better hydrophobicity. Good hydrophobicity/oleophilicity were also possible with mixed‐ligand MOFs containing metal‐binding ligands. Thus, a (super)hydrophobic MOF catalyst loaded with Pd centers efficiently catalyzed Sonogashira reactions in water at ambient temperature. Studies of the hydrophobic effects of the coordination interspace and the outer surface suggest a simple de novo strategy for the synthesis of superhydrophobic MOFs that combine surface roughness and low surface energy. Such MOFs have potential for environmentally friendly catalysis and water purification.     

pH‐ and β‐cyclodextrin‐responsive micelles based on polyaspartamide derivatives as drug carrier

A novel kind of graft polymer poly(aspartic acid)‐ethanediamine‐g‐adamantane/methyloxy polyethylene glycol (Pasp‐EDA‐g‐Ad/mPEG) was designed and synthesized for drug delivery in this study. The chemical structure of the prepared polymer was confirmed by proton NMR. The obtained polymer can self‐assemble into micelles which were stable under a physiological environment and displayed pH‐ and β‐cyclodextrin (β‐CD)‐responsive behaviors because of the acid‐labile benzoic imine linkage and hydrophobic adamantine groups in the side chains of the polymer. The doxorubicin (Dox)‐loaded micelles showed a slow release under physiological conditions and a rapid release after exposure to weakly acidic or β‐CD environment. The in vitro cytotoxicity results suggested that the polymer was good at biocompatibility and could remain Dox biologically active. Hence, the Pasp‐EDA‐g‐Ad/mPEG micelles may be applied as promising controlled drug delivery system for hydrophobic antitumor drugs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1387–1395     

Amino Acid–Substituted Dextran‐Based Non‐Viral Vectors for Gene Delivery

To form bio‐inspired non‐viral vectors for DNA delivery, the polysaccharide dextran is allowed to react with Boc‐amino protected amino acids glycine, β‐alanine, and L‐lysine activated with 1,1’‐carbonyldiimidazole and subsequent dextran ester deprotection. A library of such dextran esters is made available to investigate the relationship between polymer structure, complex formation, stability, toxicity, and transfection. Only dextran esters of β‐alanine and L‐lysine are able to efficiently interact with DNA as shown by dye exclusion assays, to form nanosized complexes (70–110 nm) with positive zeta potential. With increasing substitution degree and complex charge ratios, the L‐lysine esters accomplish more effective binding and protection of DNA against enzymatic degradation than β‐alanine esters. However, luciferase reporter gene assays reveal higher transfection for β‐alanine than for L‐lysine esters due to a more effective DNA release and better suited buffing area of the amino groups triggering the endosomal release. Conclusively, β‐alanine‐substituted dextran derivatives may serve as promising non‐viral vectors.     

Two‐Photon STED Spectral Determination for a New V‐Shaped Organic Fluorescent Probe with Efficient Two‐Photon Absorption

Two‐photon stimulated emission depletion (STED) cross sections were determined over a broad spectral range for a novel two‐photon absorbing organic molecule, representing the first such report. The synthesis, comprehensive linear photophysical, two‐photon absorption (2PA), and stimulated emission properties of a new fluorene‐based compound, (E)‐2‐{3‐[2‐(7‐(diphenylamino)‐9,9‐diethyl‐9H‐fluoren‐2‐yl)vinyl]‐5‐methyl‐4‐oxocyclohexa‐2,5‐dienylidene} malononitrile ( 1 ), are presented. Linear spectral parameters, including excitation anisotropy and fluorescence lifetimes, were obtained over a broad range of organic solvents at room temperature. The degenerate two‐photon absorption (2PA) spectrum of 1 was determined with a combination of the direct open‐aperture Z‐scan and relative two‐photon‐induced fluorescence methods using 1 kHz femtosecond excitation. The maximum value of the 2PA cross section ～1700 GM was observed in the main, long wavelength, one‐photon absorption band. One‐ and two‐photon stimulated emission spectra of 1 were obtained over a broad spectral range using a femtosecond pump–probe technique, resulting in relatively high two‐photon stimulated emission depletion cross sections (～1200 GM). A potential application of 1 in bioimaging was demonstrated through one‐ and two‐photon fluorescence microscopy images of HCT 116 cells incubated with micelle‐encapsulated dye.