Because of the advantageous properties, the photoresponsive bioinspired polymers are of great interest for many applications. In this study, we synthesized a new family of photoresponsive poly(ethylene glycol)-block-poly(o-nitrobenzyl-Lglutamate) diblock copolymers, which can self-assemble into spherical micelles in aqueous solution. Upon UV irradiation, an interesting photoinduced morphology transition from spheres to cylinders was observed arising from the disruption of amphiphilicity induced by the cleavage of o-nitrobenzyl groups on the side chains. A couple of techniques including proton nuclear magnetic resonance ( 1 H NMR) and ultraviolet−visible absorption spectra measurement (UV−vis) were used to track the process of photolysis. A systematic study on the effects of pH, molecular weights, and secondary structure on the selfassembly of diblock copolymers was performed. We demonstrate that the secondary conformation transition with pH variation dominates the sphere-to-cylinder transition. Remarkably, the hierarchical nanostructures with various dimensions can be obtained from preassembled units with the addition of metal ions.
A series of reversible crosslinking assemblies with tunable morphologies are obtained from a new family of photoresponsive polypeptoid-based diblock copolymers.
Enzyme-responsive polypeptide vesicles
have attracted considerable
attention for precision theranostics because of their biocompatibility,
biodegradability, and unique secondary conformation transition triggered
by the catalytic actions of enzymes. These promising potentials of
polypeptide vesicles could be limited in a drug delivery system by
the very slow enzyme diffusion rate into vesicles that could reduce
the efficacy of the drug. On the other hand, stimuli-responsive polymeric
vesicles that respond to stimuli can undergo microstructure destruction
for the burst release of drugs, which would penetrate through the
membrane of dead cells and the tumor extracellular matrix, inducing
acute toxicity to neighboring cells. Here, we designed amphiphilic
PEG–polypeptide copolymers containing esterase-labile carbamate-caged
primary amines. It was found that the diblock can self-assemble into
vesicular structures. Esterase-triggered self-immolative decaging
reactions could quickly release the primary amine moiety of monomers
that can undergo an amidation reaction for transition of the bilayer
of vesicles from hydrophobic to partially hydrophilic. This esterase-responsive
process retains the nanostructure of vesicles but permeabilizes the
vesicle membrane, which can afford the sustained release of encapsulating
drugs. These esterase-responsive polypeptide vesicles mediate selective
cytotoxicity in cancer cells with high esterase expression over normal
fibroblasts with low esterase, enabling the potent anticancer chemotherapy
with minimized side effects.
Background and PurposeAs the global fertility rate declines, China has issued two and three-child policies in the past 10 years. Therefore, this study serves to evaluate fertility intention rates and related factors in couples intending to have a second child and third child.MethodsA cross-sectional survey was conducted in mainland China from July to August 2021. Couples with one or two children were invited to participate in our study in order to collect information about more than one child fertility intention and the possibly related factors. Odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) were calculated and adjusted for potential confounding factors.ResultsData was collected from a total of 1,026 couples. Among couples with one child, 130 (16.2%) couples had the intention to have a second child. Additionally, only 9.4% of couples with two children desired to have third child. The study revealed large differences in socioeconomic and personal factors between the two groups. For couples with intentions for a second-child, a female age >35 years (adjusted odds ratio, aOR 1.92), a first child's age range from 3 to 6 (aOR 3.12), annual child spending as a percentage of household income >30% (aOR 2.62), and children's educational barriers (aOR 1.55) were associated with lack of intent to have a second child. Similarly, among couples with two children, parents with family financial constraints (aOR 6.18) and children's educational barriers (aOR 4.93) are more likely to have lack of intent to have a third child. Here, we report that government policies encouraging fertility (aOR 0.04) can effectly promote couples to pursue a second or third child.ConclusionOverall, couples with one or two children in Shanghai had a low intention to give birth to a second or third child. In order to increase the birth rates, it is necessary to implement policies to reduce the burden of raising children and provide relief to parent's pressure of rearing a child with increased free time.
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