No abstract

Efficient accumulation and intracellular drug release in cancer cells remain a crucial challenge in developing ideal anticancer drug delivery systems. Here, poly(N-isopropylacrylamide)-ss-acrylic acid (P(NIPAM-ss-AA)) nanogels based on NIPAM and AA cross-linked by N,N'-bis(acryloyl)cystamine (BAC) were constructed by precipitation polymerization. The nanogels exhibited pH/redox dual responsive doxorubicin (DOX) release behavior in vitro and in tumor cells, in which DOX release from nanogels was accelerated in lysosomal pH (pH 4.5) and cytosolic reduction (10 mM GSH) conditions. Moreover, intracellular tracking of DOX-loaded nanogels confirmed that after the nanogels and the loaded DOX entered the cells simultaneously mainly via lipid raft/caveolae-mediated endocytosis, DOX-loaded nanogels were transported to lysosomes and then the loaded DOX was released to nucleus triggered by lysosomal pH and cytoplasmic high GSH. MTT analysis showed that DOX-loaded nanogels could efficiently inhibit the proliferation of HepG2 cells. In vivo animal studies demonstrated that DOX-loaded nanogels were accumulated and penetrated in tumor tissues more efficiently than free DOX. Meanwhile, DOX-loaded nanogels exhibited stronger tumor inhibition activity and fewer side effects. This study indicated that pH/redox dual-responsive nanogels might present a prospective platform for intracellular drug controlled release in cancer therapy.

Topographical guidance and chemotaxis are crucial factors for peripheral nerve regeneration. This study describes the preparation of highly aligned poly(ε-caprolactone) (PCL) fiber conduits coated with a concentration gradient of nerve growth factor (NGF) (A/G-PCL) using a newly designed electrospinning receiving device. The A/G-PCL conduits are confirmed in vitro to enhance and attract the neurite longitudinal growth of dorsal root ganglion (DRG) neurons toward their high-concentration gradient side. In vivo, the A/G-PCL conduits are observed to direct a longitudinal stronger attraction of axons and migration of Schwann cells in 15 mm rat sciatic nerve defects. At 12 weeks, rats transplanted with A/G-PCL conduits show satisfactory morphological and functional improvements in g-ratio, total number, and area of myelinated nerve fibers as well as the sciatic function index, compound muscle action potentials, and muscle wet weight ratio as compared to aligned PCL fibers conduits with uniform NGF (A/U-PCL). The performance of A/G-PCL is similar to that of autografts. Moreover, mRNA-seq and RT-PCR results reveal that Rap1, MAPK, and cell adhesion molecules signaling pathways are closely associated with axon chemotactic response and attraction. Altogether, by combining structural guidance with axon chemotaxis, the NGF-gradient/ aligned PCL fiber conduits represent a promising approach for peripheral nerve defect repair.

Methylation at the N1 site of adenine leads to the formation of cytotoxic 1-methyladenine (m1A). Since the N1 site of adenine is involved in the hydrogen bonding of TAEA and AAET Watson-Crick base pairs, it is expected that the pairing interactions will be disrupted upon 1-methylation. In this study, high-resolution NMR investigations were performed to determine the effect of m1A on double-helical DNA structures. Interestingly, instead of disrupting hydrogen bonding, we found that 1-methylation altered the TAEA Watson-Crick base pair to T(anti)AEm1A(syn) Hoogsteen base pair, providing insights into the observed differences in AlkB-repair efficiency between dsDNA and ssDNA.