Application and prospect of three-dimensional printing in bone tissue engineering / 国际生物医学工程杂志

In this paper,the classification,application and advantages of three-dimensional (3D) printing in biomedical engineering are summarized.The working principles of 3D printing,stereolithography,fused deposition modeling,selective laser sintering and 3D spray printing,as well as merits,demerits and recent progress are reviewed.The 3D printing has been widely used in the synthetic of bone tissue engineering scaffolds,with biodegradable and bioactive materials in the scaffold.Synthetic bone materials and surgical simulation by 3D printing technology are increasingly common and has achieved satisfactory results in China.Although 3D printing technology has developed rapidly,development of suitable biomaterials and improving relevant techniques are still urgent issues.Up to now,the functionalization of bionic organs is the most difficult issue,in which the cell co-culture,vascularization and preparation of the scaffolds are problem to be solved.The 3D printing technology will make remarkable achievements for the regeneration and repair of human organ through our efforts.

DNA methylation and telomere damage in occupational people exposed to coal tar pitch / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the promoter methylation of p16, FHIT and RASSF1A gene and telomere damage in the workers exposed to coal tar pitch, and to explore the effective biomarker of occupational exposure to coal tar pitch.</p><p><b>METHODS</b>180 cases of workers exposed to coal tar pitch in a certain carbon plant named as exposure group, and 145 healthy cases with a medical examination in the first affiliated hospital of Zhengzhou University were selected as control group. Relative telomere length in peripheral blood DNA was detected using real-time quantitative PCR, and the promoter methylation rate of p16, RASSF1A and FHIT gene in peripheral blood DNA were determined by real-time quantitative methylation specific PCR. The relative telomere length and gene promoter methylation in two groups were compared, and influencing factors were analyzed.</p><p><b>RESULTS</b>Relative telomere length in exposed group was lower than that in the control group, and the difference was statistically significant (Z = -5.395, P < 0.001). There was no significant difference in the promoter methylation rate of p16, FHIT and RASSF1A gene between the two groups (P > 0.05). Stratification analysis by gender, age, and smoking, we found that when the age was less than or equal to 40, the promoter methylation rate of p16 in exposed group was more than that in control group, and the difference was statistically significant (Z = -1.914, P = 0.011).</p><p><b>CONCLUSION</b>Occupational exposure to coal tar pitch may induce leukocyte DNA telomere length of human peripheral blood shortened, and may not change the promoter methylation rates of p16, FHIT and RASSF1A gene.</p>

Factors and mechanism influencing elastin-like polypeptides self-assembled into micron-sized particles / 生物工程学报

Many factors influence the elastin-like polypeptides (ELPs) self-assembled into micron-sized particles. However, few efforts were made to investigate these factors. Using the ELPs [KV8F]n as the target, we studied systematically the factors with the dynamic light scattering. Our results show that the particle size increased and the uniform of particles decreased with the increase of the molecular weight. The analysis of size variation in self-assembled ELPs in response to changes in salt concentration indicated that the size increased with increasing the salt concentration, and the opposite response was observed when the concentration was above 0.4 mol/L. Under these conditions, the particles are micron-sized and larger than 1.1 μm. However, when the fusions containing the same ELPs and xylanase or 1,3-propanediol oxidoreductase, the size of the self-assembled ELPs particles decreased dramatically, which was only about 1/10 of that of the free ELPs. We proposed that the solvent accessible charged area of the enzymes could interact with the ELPs, the sterical hindrance of the enzymes prevent the aggregation of the ELPs. This might be the most important parameter in altering the particle size sharply.

Research progress in co-delivery of gene and chemotherapy drugs with nanocarriers for cancer therapy / 药学学报

Current trends in nanotechnology and RNA interference technology have made the application of nanocarriers (NCS) as a novel gene and drug delivery systems very promising for the field of multidrug resistance (MDR) cancer treatment. Co-delivery of gene and chemotherapy drugs with NCS has a good synergistic effect compared with the traditional chemotherapy which can increase the amount of the drug distribution in target organ in order to reduce the toxic side effects thereby enhancing efficacy. Therefore, the advent of co-delivery systems with NCS especially in the clinical treatment of MDR has had a significant impact on the cancer treatment.

Progress in microencapsulation of stem cells / 生物工程学报

For the regenerative therapy of refractory diseases, stem cells have become an excellent source of seed cells due to their strong self-renewal and multi-differentiation abilities. Microcapsules can provide a three-dimensional growth environment with a good immunoisolation and biocompatibility for cells, and the microencapsulation of stem cells provides a new technical support for large-scale cell culture with high activities in vitro and long-term preservation, consequently opening up a new alternative for cell transplantation. In this review, we first outlined the development of microencapsulation, then introduced the present materials and methods for the microencapsulation of stem cells and its immunoisolation, and discussed the progress in microencapsulation technology, various types of stem cell used in recent years in details. Finally, we addressed perspectives of stem cell microencapsulation technology.

Application of molecular markers to evaluation of molecular biocompatibility of biomaterial / 国际生物医学工程杂志

The evaluation of biomaterial biocompatibility is a key step before the clinical application.With the rapid development of molecular biology,scientists have begun to evaluate biomaterial biocompatibility at molecular level and proposed the concept of molecular biocompatibility.Researchers'main tasks at present are to identify more molecular markers using molecular biology technology and to establish standards for evaluating molecular biocompatibility of biomaterial,which will provide the guidance for the design of better biomaterials.

Effect of steep pulsed electric fields on the immune response of tumor-bearing Wistar mice / 生物医学工程学杂志

This study sought to evaluate the effect of steep pulsed electric fields (SPEFs) on the immune response of Wistar mice inoculated with Walker256 sarcoma. Thirty mice were randomly divided into three groups: control group (group A, inoculated with Walker256 sarcoma, not treated), treatment group (group B, inoculated with Walker256 sarcoma, treated by SPEFs), and normal control group (group C, inoculated with normal saline, not treated). Tumor size was measured before and every 3 days after treatment by vernier caliper. MTT methods were used to assess the lymphocytes proliferation and the natural killer (NK) cells activity. TNF-a activity was measured by ELISA. Statistical analysis was performed utilizing the SPSS10.0 software package. The experiment results revealed that tumor growth was significantly inhibited in group B as compared with group A (P < 0.01), and that lymphocytes proliferation, NK cells activity and TNF-a activity in group B were not significantly different from those in group C (P = 0.953, P = 0.130, P = 0.080, respectively) but markedly higher than those in group A (P < 0.05). The results also showed that SPEFs could not only kill tumor cells but also induce antitumor immune response and improve the immune function of the host efficiently.

Development of biodegradable polymers as drug carriers / 国际生物医学工程杂志

Biodegradable polymers as drug delivery systems have attracted investigators. They degrade in biological fluids to produce biocompatible and nontoxic products, which could be removed from the body by normal physiological pathways without extra surgical removal. In this article, literatures on biodegradable polymers mainly served as matrix in controlled release systems are analyzed and reviewed.

A qualitative study of in vivo pulsed electric field distribution model in rabbit liver tissues / 生物医学工程学杂志

Pulsed electric fields (PEFs) with fixed frequency, width and gradually increased peak value of voltage was applied to 30 healthy rabbit liver tissues. The specific aims were to explore the feasibility of establishing a model of in vivo PEFs distribution in healthy rabbit liver tissues and to provide important references for clinical electrochemotherapy and for electrotransfer. Repeated experiment and self-comparison statistics design were implemented. The rabbit underwent the experiment under intravenous anesthesia and their liver tissues, after exposure to PEFs, were sent for HE staining. Necrotic borderline was visible 3 days after PEFs application, the necrotic shape of concentric circle was evident around the electrodes under optical microscope at lower voltage, as voltage increasing, two necroses in the shape of concentric circle gradually enlarged; nuclei with chromatin condensation, fragmentation and lysis alterations were seen in the middle region between the needles; concentric circles changed into ellipse fusiform and finally overlaped each other forming irregular necrosis contours. Cell cavitation and tissues ischemia were also observed within electric field. The shape of tissue necrosis from the experiment was noted to correlate with theoretic simulation of electric field distribution. Therefore, rabbit liver tissues can be a good carrier for in vivo modeling of electric field distribution when the lethal effects of PEFs in tissues are investigated. PEFs also show safety for the surrounding normal tissue while causing damage or injury to the target area therapeutically.

Comparison of tensionfree herniorrhaphy with conventional herniorrhaphy for inguinal hernia / 中国普通外科杂志

ObjectiveTo evaluate the value of tensionfree herniorrhaphy for inguinal hernia. Methods(1)Comparison was made in operating time, early postoperative response, hospitalization time, postoperative complications and recurrence rate between the two herniorrhaphy groups.In tensionfree herniorrhaphy group( n=137),hernias were repaired with polypropylene mesh plug or mesh patch.(2)In conventional herniorrhaphy group (n=98 ) ,hernias were repaired with Bassini operation. Mean Follow up time was 22 month in the 2 groups. Results The operating time, analgesic use, early response and hospitaliz ation time in tensionfree herniorrhaphy group were significantly lower than those in conventional herniorrhaphy group(P