A cross-linking reagent is required to improve mechanical strength and degradation properties of biopolymers for tissue engineering. To find the optimal preparative method, we prepared diverse genipin-cross-linked chitosan/collagen scaffolds using different genipin concentrations and various cross-linking temperatures and cross-linking times. The compressive strength increased with the increasing of genipin concentration from 0.1 to 1.0%, but when concentration exceeded 1.0%, the compressive strength decreased. Similarly, the compressive strength increased with the increasing of temperature from 4 to 20°C, but when temperature reached 37°C, the compressive strength decreased. Showing a different trend from the above two factors, the effect of cross-linking time on the compressive strength had a single increasing tendency. The other results also demonstrated that the pore size, degradation rate and swelling ratio changed significantly with different cross-linking conditions. Based on our study, 1.0% genipin concentration, 20°C cross-linking temperature and longer cross-linking time are recommended.

Object Recent studies have suggested that genetic risk factors play an important role in the occurrence of low-back pain (LBP) and lumbar disc disease. The authors' study aimed to assess the association between 3 single-nucleotide polymorphisms (SNPs) and susceptibility to LBP related to military training. Methods In this case-control study, data from 892 Chinese male soldiers were retrospectively reviewed. The case group was made up of 305 soldiers with LBP related to military training and a control group of 587 soldiers without constant LBP for more than 2 weeks. Genomic DNA was extracted from peripheral blood leukocytes of all subjects and polymerase chain reaction products were genotyped. Results No association was found between the SNP of interleukin-1β (IL-1β; +3954C/T) and LBP at both the genotypic (p = 0.104) and the allelic (p = 0.098) level. However, the G allele of caspase-9 (CASP-9) and the T allele of growth differentiation factor 5 (GDF5) were more common in patients with LBP than in patients without LBP (p < 0.001). Conclusions The findings in a Chinese military cohort indicated that CASP-9 (−1263A/G) and GDF5 (+104T/C) polymorphisms are associated with a susceptibility to LBP related to military training.

Our results suggested that the GDF5 polymorphism is associated with a susceptibility to symptomatic lumbar disc herniation in the Chinese Han population and type II collagen in the nucleus pulposus may be a key factor in susceptibility to symptomatic lumbar disc herniation.