A novel process for producing cubic liquid crystalline nanoparticles (cubosomes) has been developed. The process entails simple mixing of two waterlike solutions with a minimal input of energy. The key to this process is the inclusion of hydrotrope. Most lipids, such as monoolein, used to form cubic liquid crystals are essentially insoluble in water. The hydrotrope dissolves the lipid to create a waterlike solution. Water is added to the hydrotrope solution, resulting in a precipitous decrease in lipid solubility. Provided that the dilution trajectory falls into a cubic phase-water miscibility gap, nanometer-scale cubic liquid crystalline particles form spontaneously, presumably from a homogeneous nucleation mechanism. The process is versatile enough to accommodate any lipid and hydrotrope combination that forms cubic liquid crystalline material upon dilution. Actives and stabilizers can be formulated into either of the two solutions, allowing the production of colloidally stabilized, controlled-release dispersions. The phase diagram of the monooleinethanol-water system is determined to assess appropriate formulation of solutions and to develop dilution trajectories. This process replaces current processes that require long hold times, processing of solidlike materials, and very high-energy inputs to create cubosome nanoparticle dispersions. This process produces smaller, more stable cubosomes than by conventional bulk dispersion techniques.

cess, was observed. This may be due to a side reaction during the irradiation with 254-nm light. The photodimer may produce photodimerization by another remaining double bond on prolonged irradiation. Thus, the absorption peak at 270 nm decreased gradually on continued irradiation. ConclusionsPrevious studies in the intermolecular reactions of LB films have been limited mainly to photopolymerization and photodimerization. In this study, the intermolecular photoreversible reaction in an LB films has been found for the first time, although the photoreversible reaction of cinnamylideneacetic acid has already been known in polymer film or in low-temperature glassy matrix. Originally, one might expect that these photoreversible systems are more favorable in LB films than in polymers. However, the reversibility was still low for the LB film of 2a, similarly to the polymer film of poly(vinyl cinnamylideneacetate). This is due to the overlapping of the absorption spectra of 2a and the photodimer of 2a and also to the side reaction arising from the chromophore containing two double bonds. Therefore, further investigations are required to find other chromophores for the improvement of reversibility.(41) MS IR, and *H and 13C NMR spectra for the compounds (four acids and their methyl or ethyl esters) in this work are saved in the Spectral Data Bank System (SDBS) constructed by our laboratory (NC-LI) in the Research Information Processing System (RIPS) of Tsukuba Research Center. The spectral patterns for the compounds are available on request.

In this report, four new poly(d-glucaramidoamine)s (1-4) have been designed to lower the toxicity of conventional polymeric nucleic acid delivery vehicles by incorporating a carbohydrate comonomer within a polyethylenimine (PEI)-like backbone. Polymers 1-4 were synthesized via polycondensation of esterified d-glucaric acid and four different amine-containing comonomers [diethylenetriamine (1), triethylenetetramine (2), tetraethylenepentamine (3), and pentaethylenehexamine (4)] in methanol. Viscometry and NMR studies suggest that the polymers are mostly linear (for 1-4, the alpha value in the Mark-Houwink-Sakurada equation = 0.6-0.7), thus indicating that polymerization occurs predominantly through the primary amines with a low degree of branching off the secondary amines. Results of gel electrophoresis shift assays show that polymers 1-4 bind pDNA at N/P ratios of 5, 3, 2, and 2, respectively. Also, dynamic light scattering and TEM experiments indicate that 1-4 compact DNA into nanoparticles (polyplexes) between 140 and 440 nm at an N/P ratio of 30. Furthermore, polyplexes formed with 1-4 deliver pDNA (plasmid DNA) containing the firefly luciferase reporter gene to BHK-21 cells in a nontoxic and highly efficient manner (as determined by luciferase gene expression). In particular, polymer 4 reveals very high delivery efficiency (equivalent to linear PEI). This result may be due in part to the "proton sponge" hypothesis proposed by Behr et al. Polymers containing amines that are protonated in the endosomal pH range (between about 7.4-5.0) reveal enhanced gene delivery profiles.

There is considerable interest in the binding and condensation of DNA with polycations to form polyplexes because of their possible application to cellular nucleic acid delivery. This work focuses on studying the binding of plasmid DNA (pDNA) with a series of poly(glycoamidoamine)s (PGAAs) that have previously been shown to deliver pDNA in vitro in an efficient and nontoxic manner. Herein, we examine the PGAA-pDNA binding energetics, binding-linked protonation, and electrostatic contribution to the free energy with isothermal titration calorimetry (ITC). The size and charge of the polyplexes at various ITC injection points were then investigated by light scattering and zeta-potential measurements to provide comprehensive insight into the formation of these polyplexes. An analysis of the calorimetric data revealed a three-step process consisting of two different endothermic contributions followed by the condensation/aggregation of polyplexes. The strength of binding and the point of charge neutralization were found to be dependent upon the hydroxyl stereochemistry of the carbohydrate moiety within each polymer repeat unit. Circular dichroism spectra reveal that the PGAAs induce pDNA secondary structure changes upon binding, which suggest a direct interaction between the polymers and the DNA base pairs. Infrared spectroscopy experiments confirmed both base pair and phosphate group interactions and, more specifically, showed that the stronger-binding PGAAs had more pronounced interactions at both sites. Thus, we conclude that the mechanism of poly(glycoamidoamine)-pDNA binding is most likely a combination of electrostatics and hydrogen bonding in which long-range Coulombic forces initiate the attraction and hydroxyl groups in the carbohydrate comonomer, depending on their stereochemistry, further enhance the association through hydrogen bonding to the DNA base pairs.