[Progress in research and development of soft tissue three-dimensional bioprinting and its supporting equipment]

As a cutting-edge technology of tissue engineering, three-dimensional bioprinting can accurately fabricate biomimetic tissue, which has made great progress in the field of hard tissue printing such as bones and teeth. Meanwhile, the research on soft tissue bioprinting is also developing rapidly. This article mainly discussed the development progress in various bioprinting technologies and supporting equipment including printing software, printing hardware, supporting consumables, and bioreactors for soft tissue three-dimensional bioprinting, and made a prospect for the future research and development direction of soft tissue three-dimensional bioprinting.

[Research advances on the application of natural and recombinant collagen in wound repair]

Collagen is a macromolecular protein constituting the extracellular matrix of animal connective tissue, which has been widely used and developed in fields of biomedicine, tissue engineering, food, and cosmetics. Due to its advantages such as abundant sources and good biocompatibility, low immunogenicity, and degradability, collagen can be used as a dressing or tissue engineering scaffold for wound repair. According to the source of materials, collagen can be divided into natural collagen and recombinant collagen. Natural collagen is mainly extracted directly from mammals and fish; recombinant collagen is obtained based on genetic engineering technology, and its sources include recombinant expression systems of microorganisms, animals, and plants. This paper summarizes the sources of collagen, and the roles, advantages, and disadvantages of different sources of collagen in wound repair, the particularity and superiority of collagen combined with three-dimensional printing technology in wound repair, the impact of market norms of China's collagen industry on the field of wound repair, and explains the precautions for the development of collagen-related products, aiming to provide new ideas for selecting a suitable source of collagen for wound repair.

Two-step aggregation of gold nanoparticles based on charge neutralization for detection of melamine by colorimetric and surface-enhanced Raman spectroscopy platform

A colorimetric and surface-enhanced Raman scattering (SERS) signal amplification platform based on 2-step aggregation of gold nanoparticles (AuNP) was constructed for the sensitive detection of melamine. In this study, the positively charged SYBR Green I was used for the first step of aggregation of AuNP, via charge neutralization, to obtain small-sized AuNP aggregates. The positively charged SYBR Green I decreased the negative charges of the surface of AuNP, which was beneficial to the aggregation of AuNP. In addition, the melamine could aggregate AuNP by decreasing the negative charges of the surface of AuNP and self-assemble with each other on the surface of AuNP by hydrogen bonds. Therefore, the second efficient aggregation of small-sized AuNP aggregates could be achieved with melamine at low concentration, resulting in significant signal changes of color and SERS. The sensitivity of a colorimetric (0.60 mg/L) and SERS (0.089 mg/L) platform, based on 2-step aggregation of AuNP, was 15 and 2.2 times higher than that based on 1-step aggregation of AuNP for detecting melamine.

A review on efficient removal of phthalic acid esters via biochars and transition metals-activated persulfate systems

As emerging contaminants, PAEs (Phthalic Acid Esters or Phthalate Esters) have been extensively utilized in industrial production to soften the rigid plastics (plasticizers), and their related products are widely distributed in our daily life. The PAEs can readily transfer from the products to the surrounding environment due to not being chemically bound to the products. In this study, we analyzed the PAEs' properties, usage, and consumption in the world, as well as toxicity to human beings. As endocrine-disrupting chemicals (EDCs), PAEs can disturb the normal hormones reactions, resulting in developmental and reproductive problems. Thus, we have to concern the removal strategies of PAEs. We summarized two novel approaches, including biochars and persulfate (PS) oxidation for effectively removing PAEs in the literature. Their characteristics, removal mechanisms, and the main impact factors on the removal of PAEs were highlighted. Moreover, transition metal-activated PS showed good performance on PAEs degradation. Furthermore, the synergy of biochars and transition metals-PS can overcome the disadvantages of a single approach, and show better performance on the removal of PAEs. Finally, we put forward vital strategies to update two approaches (including the combined) for enhancing the removal of PAEs. It is expected that the researchers or scientists can get a hint on effectively remediating PAEs-contaminated sites via the biochars' sorption/transition metals-PS or the combined two from this review paper.

[Analysis of invalid patents associated with schistosomiasis control filed by Chinese applicants]

The invalid patents associated with schistosomiasis control were retrieved in the Chinese Patent Database of China National Intellectual Property Administration, the Baiten database and the incoPat database, and the overall trends, legal status, types, patent indexing and technical fields of all retrieved invalid patents were analyzed. As of December 30, 2020, there were totally 859 patents relating to schistosomiasis control, and 512 were invalid patents, with an invalid rate of 59.6%. The number of patent applications and invalid patents peaked in 2018, including 71 patent applications and 53 invalid patents. Among the 511 schistosomiasis control-related invalid patents with complete records, there were 425 invention patents, 81 utility model patents and 5 design patents, and 219 patents (42.9%) were invalid due to the termination of the patented right and 292 (57.1%) due to loss of the right for patent applications. The major technical points included medicines (chemicals), basic research, devices and detections, and the specialized fields were mainly concentrated in A61P33, G01N33, C12N15, C07K14 and A01N65. Our data demonstrate a high invalid rate of patents relating to schistosomiasis control in China. Secondary development and mining of the invalid patents in relation to schistosomiasis are recommended to make use of their values in the national schistosomiasis elimination program of China.

Frequency Characteristics of AEPs in Normal Young Adults and Comparison of Their Response Threshold and Pure Tone Audiometry Threshold

Objective The tests of three types of auditory evoked potentials （AEPs） were performed on normal young adults, to understand the frequency characteristics of different testing methods and the relationship between response threshold and pure tone audiometry threshold of different methods, and to discuss the forensic value of 3 types of AEPs to evaluate hearing function. Methods Twenty normal young adults were selected, their standard pure tone audiometry threshold, short-term pure tone audiometry threshold and the response threshold of 3 types of AEPs （tone burst-auditory brainstem response, 40 Hz auditory event-related potential and slow vertex response） at 0.5 kHz, 1.0 kHz, 2.0 kHz and 4.0 kHz were recorded. The relationship between the response threshold and standard pure tone audiometry threshold, short-term pure tone audiometry threshold of 3 types of AEPs at different frequencies as well as the differences between different types of AEPs were analyzed. Results The short-term pure tone audiometry threshold was higher than the standard pure tone audiometry threshold at each frequency. The response threshold and standard pure tone audiometry threshold of the 3 types of AEPs all had a certain correlation, and the response threshold of the 3 types of AEPs was higher than short-term pure tone audiometry threshold and standard pure tone audiometry threshold at each frequency. The differences in the differences between the response threshold and standard pure tone audiometry threshold of the 3 types of AEPs at different frequencies had statistical significance. Linear regression mathematical models were established to infer the standard pure tone audiometry threshold （hearing level） from response threshold （sound pressure level） of 3 types of AEPs of normal young adults. Conclusion When using response threshold of different types of AEPs to estimate pure tone audiometry threshold, conversion and correction are needed. Combined use of different types of AEPs could improve the accuracy of hearing function evaluation.

Impact of water quality on the microbial diversity in the surface water along the Three Gorge Reservoir (TGR), China

The Three Gorges Reservoir (TGR), one of the world's largest reservoirs, has crucial roles in flood control, power generation, and navigation. The TGR is contaminated because of the human activities, and how the contaminated water influences the distribution of the microbial community have not been well studied. In this study, we collected 41 freshwater samples from 13 main dwelling districts along the TGR to investigate the water quality, the distribution of the microbial community, and how water quality affects the microbial community structure. The sampling sites cover the whole TGR along the stream, with 670 km distance. Our results show that both water quality and the compositions of bacterial community vary along the TGR. The distribution of bacterial community is closely related to the local water quality. There is the highest concentration of chemical oxygen demand (COD), the highest relative abundance of Firmicutes, and the highest relative abundance of Bacillus in the upstream, compared to the middle and down streams. Redundancy analysis (RDA) showed that PO₄^3- and COD were the main environmental factors influencing on the structure of bacterial community. The relative abundance of nitrification and denitrification functional genes also altered along the streams. These findings provide the basic data for water quality, the distribution of bacterial community, the link of environmental factors, and the bacterial community structure along the TGR, which guides the local environmental protection agency to launch protection strategy for maintaining the ecosystem health of the TGR.

Urethral reconstruction using bone marrow mesenchymal stem cell- and smooth muscle cell-seeded bladder acellular matrix

BACKGROUND

Congenital or acquired abnormalities may lead to a urethral defect that often requires surgical reconstruction. The traditional methods often lead to complications, including urethrocutaneous fistulae and strictures. In this study, we proposed to construct a tissue-engineered sheet graft (TESG) using a bone marrow mesenchymal stem cell (BMSC)- and smooth muscle cell (SMC)-seeded bladder acellular matrix (BAM) for urethral reconstruction.

METHODS

Rabbit BMSCs and SMCs were isolated, expanded, and identified in vitro before seeding into BAM as the experimental group, whereas BAM-only was the control group. The graft was used to construct TESG for implantation into the rabbit omentum for 2 weeks before urethral reconstruction. We divided 24 male rabbits into four experimental groups six each, and six other were the control group. Histological analysis was performed at 2 weeks, 4 weeks, 8 weeks, and 16 weeks postoperatively. Retrograde urethrography was performed at 16 weeks postoperatively.

RESULTS

All experimental rabbits survived to they were humanly killed. At 8 weeks, there was no difference between the graft and the normal urethra with no severe shrinkage. At 8 and 16 weeks after TESG grafting in vivo, multilayer urothelium covered the graft, neovascularization was visible within the center of TESG, and organized smooth muscle bundles were present. Retrograde urethrography failed to demonstrate diverticula formation or urethral stricture. Three control rabbits died within 4 weeks postoperatively. Autopsy showed their urethras to be almost completely blocked whereas another three hosts displays urethral strictures.

CONCLUSION

A TESG was constructed using a BMSC- and SMC-seeded BAM for urethral reconstruction.

Desorption and ripening of low density InAs quantum dots

In this paper, combining low deposition rate with proper growth temperature, we have developed a way to prepare very low-density quantum dots (QDs) suited for the study of single QD properties without resorting to submicron lithography. Experiment results demonstrate that InAs desorption is significant during growing the low density QDs. Ripening of InAs QDs is clearly observed during the post-growth annealing. Photoluminescence spectroscopy reveals that the emission wavelength of low density InAs QDs arrives at 1332.4 nm with a GaAs capping layer.

Long-wavelength emission InAs quantum dots grown on InGaAs metamorphic buffers

In this work, InAs quantum dots (QDs) grown on a linear graded InGaAs metamorphic buffer layer by molecular beam epitaxy have been investigated. The growth of the metamorphic buffer layers was carefully optimized, yielding a smooth surface with a minimum root mean square of roughness of less than 0.98 nm as measured by atomic force microscopy (AFM). InAs QDs were then grown on the buffer layers, and their emission wavelength at room-temperature is 1.49 microm as measured by photoluminescence (PL). The effects of post-growth rapid thermal annealing (RTA) on the optical properties of the InAs QDs were investigated. After the RTA, the PL peak of the QDs was blue-shifted and the full width at half maximum decreased.

Characteristics of cadmium uptake and accumulation by two contrasting ecotypes of Sedum alfredii Hance

The mined ecotype of Sedum alfredii Hance has been identified to be a zinc (Zn) hyperaccumulator native to China. In the present article, the characteristics of cadmium (Cd) uptake and accumulation were compared with hydroponic experiments between the mined and the nonmined ecotypes of Sedum alfredii Hance. The results indicate that the plants of the mined ecotype (ME) have higher tolerance of Cd than the plants of the nonmined ecotypes (NME) in terms of dry matter yield. The thresholds of external Cd levels for the reduction of plant growth were 100 micromolL(-1) for the NME and 400 micromolL(-1) for the ME, respectively. Kinetic study showed that the rates of Cd influx into roots (IR) and transport to shoots (TR) were higher in the ME than in the NME, with 5-fold higher for the maximum IR (Imax) and 13-fold higher for the maximum TR (Tmax) in the NME, respectively. Cadmium concentrations increased with increasing external Cd supply levels. Root Cd concentrations in the NME were higher than that in the ME, with a maximum being 5646 mg kg(-1) for the NME and 2889 mg kg(-1) for the ME at 1000 micromolL(-1) Cd. On the contrary, shoot Cd concentrations of the NME were far lower than that of the ME. Maximum shoot Cd concentrations were 533 mg kg(-1) in leaves and 935 mg kg(-1) in stems at 1000 micromol L(-1) Cd for NME, whereas, 4933 and 3874 mg kg(-1) at 400 micromol L(-1) Cd for the ME, respectively. Meanwhile, Cd concentrations in the shoots of both the NME and ME increased with advancing Cd treatment time. At 100 micromolL(-1) Cd, concentrations of Cd in leaves and stems of the NME sharply increased within initial 8 and 12 days, and those in the ME increased dramatically until D20 and D16, respectively. However, leaf and stem Cd concentrations reached their maximum values on D4 for the NME and D8 for the ME, respectively, when the plants were exposed to 1 micromol L(-1) Cd. Cadmium accumulation by plant shoots was obvious higher in the ME than in the NME at varied Cd supply levels or Cd treatment time. The maximum Cd taken up by the shoots was 1032 microg plant(-1) in concentration-dependent uptake, and 1699 microg plant(-1) in time-course uptake for the ME, with 15-fold and 18-fold higher than those for the NME, respectively. The ratios of shoot/root of Cd ranged from 12 to 39, varying with Cd supply levels, and from 13 to 24 in the varied treatment times for the ME, more than 10 times greater than those for the NME. In addition, Cd distribution in leaves, stems and roots of ME was greatly different from those of NME. The percentage of Cd distribution in shoots was more than 79 at the varied Cd supply levels, or 83 in the varied treatment time for ME, both higher than that for NME. It could be concluded that the mined ecotype of Sedum alfredii Hance has a greater ability to tolerate, transport, and accumulate Cd, as compared with the nonmined ecotype.

Transperineal end-to-end anastomotic urethroplasty for traumatic posterior urethral disruption and strictures in children

OBJECTIVE

To report the long-term results of transperineal end-to-end anastomotic urethroplasty for post-traumatic posterior urethral stenosis in children.

METHODS

From 1975 to 1996, 25 boys [aged 3 to 12 years] with post-traumatic posterior urethral stenosis or obliteration, and one boy [aged 7 years] with disrupted posterior urethra were treated with transperineal end-to-end anastomotic urethroplasty. Final follow-up assessments including voiding status, urinary continence and erectile function were performed in June 1999.

RESULTS

Smooth voiding was restored in 25 boys postoperatively. one child failed an ill-prepared repair and was waiting for further intervention. Among the 25 patients, seven were lost to the final follow-up. All seven boys had a single urethroplasty for simple urethral stenosis and had been followed for 3 to 5 years postoperatively with smooth voiding. The other 18 boys, including seven with complex urethral stenosis [three with a history of failed previous urethroplasties, three with urethrorectal fistula and one with urethroperineal fistula], underwent a total of 22 end-to-end anastomotic urethroplasties [one successful primary repair, 17 successful delayed repairs and four failed repairs]. Of the 17 patients with successful delayed repair, 14 succeeded with one repair, two with two repairs and one with three repairs. The success rate per repair for simple urethral strictures was 94.7% [18 of 19], and for complex strictures 63.6% [7 of 11]. Stress incontinence was found in three cases, impotence in two. Concomitant impotence and stress incontinence were found in one of the five patients.

CONCLUSION

Transperineal end-to-end anastomotic urethroplasty can achieve good long-term outcomes in children with simple post-traumatic posterior urethral stenosis. In experienced hands, good results can also be achieved for complex urethral strictures.