A mechanical investigation of reworkable resins was carried out using a reworkable monomer as an adhesive. A methacrylate monomer which has both an epoxy moiety and a thermally cleavable tertiary ester moiety in a molecule was employed as the reworkable monomer. The lap shear adhesion strength of the cured reworkable monomer decreased after decomposition by photo-irradiation followed by baking. The decrease revealed by FT-IR measurements was due to the acid-catalyzed decomposition of the tertiary ester linkages in the cured reworkable monomer.
Controlling the aspect ratio of polyplexes
prepared by mixing pDNA
with a polycation mixture of a poly(l-lysine) (PLL) homopolymer
and PLL terminally bearing a multiarm poly(ethylene glycol) (PEG)
part (maPEG–PLL) was examined. By varying the maPEG–PLL
content in the polycation mixture, the condensation of pDNA accompanied
by polyplex formation and the morphology of the polyplexes were evaluated
by a dye exclusion assay and AFM observations, respectively. Increasing
the maPEG–PLL content caused elongation of the polyplex, and
polyplexes with aspect ratios from 2 to 10 were prepared successfully
by controlling the maPEG–PLL content. The reactivity of pDNA
in the polyplexes with varying aspect ratios against DNase I and polymerase
were examined by agarose gel electrophoresis and real-time PCR measurements,
respectively. Moreover, cellular uptake and transfection efficiency
of the polyplexes by HeLa cells was evaluated. The results revealed
that an increase in aspect ratio of the polyplexes caused an increase
in PCR efficiency with a concomitant decrease in cellular uptake.
Radical copolymerization of N‐substituted maleimides (RMIs) and maleic anhydride (MAn) in combination with 2,4‐dimethyl‐1,3‐pentadiene (DMPD) and 1,3‐pentadiene (PD) provides alternating copolymers with excellent thermal stability. Onset temperatures of decomposition are 280–331 and 336–371 °C for the copolymers with DMPD and PD, respectively. Glass transition temperatures of RMI copolymers are in a wide range of 54–138 °C depending on the bulkiness of N‐substituents. MAn copolymers are transformed to the corresponding RMI copolymers by postpolymerization reactions, which consist of quantitative addition of an alkylamine to an anhydride moiety of MAn copolymers and the subsequent heating. The copolymers synthesized in this study include ozone‐degradable carbon‐to‐carbon double bonds in their main chain. Molecular weight of the copolymers rapidly decreases by ozone degradation. Surface modification of casted polymer films is also performed by exposure to ozone‐containing air.
For the development of an effective nonviral gene vector, ternary complexes were prepared through the compaction of nanofiber-polyplexes. These were formed using pDNA and a head-tail type polycation bearing a multi-arm poly(ethylene glycol) head and a poly(l-lysine) tail, and this strategy was based on the crowding effect of poly(ethylene glycol) in the polyplex. Mixing was carried out using a cationic lipid (lipofectamine), which is a commercially available transfection reagent. Through ternary complex formation, the elongated morphology of nanofiber-polyplexes was found to compact into a spherical shape with an average diameter of ca. 100 nm. Accompanying ternary complex formation, the compaction of the nanofiber-polyplexes can improve cellular uptake and helps the ternary complex to retain its smooth transcription/translation process, which is characteristic of nanofiber-polyplexes. As a result, ternary complexes prepared at an optimal mixing ratio exhibit a high transfection efficiency compared with lipofectamine lipoplexes.
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