Lu Wang

Promoted dermis healing from full-thickness skin defect by porous silk fibroin scaffolds (PSFSs).

Studies on skin substitutes and dermal scaffolds have been extensively carried out in the past several decades and some commercial products derived from collagen and polymers have been in marketing. Yet little research on silk fibroin based dermal scaffolds and products has been reported so far. In the present study, therefore, porous silk fibroin scaffolds (PSFSs) have been prepared by freeze drying method. The effects of PSFSs on skin recovery from full thickness defect have been examined by histological evaluation with respect to neovascularization, dermal regeneration and infiltration of inflammatory cells. In addition, tissue compatibility between PSFSs and polyvinyl alcohol (PVA) sponges (as control) has been semiquantitatively compared by scoring method. The results showed that at day 18 after implantation, new tissues formed in PSFSs whose structure was almost equal to normal skin structure where proportional distribution of functional blood vessels could be found. Furthermore, infiltration of inflammatory cells in PSFSs disappeared within 7 days. By contrast, a variety of interstices, fibrous encapsulization and moderate infiltration of inflammatory cells could be found in PVA sponges at day 18 after implantation. In summary, PSFSs has significantly promoted the skin recovery from full thickness defect, showing fibroins outstanding tissue compatibility.

In vivo biodegradation of porous silk fibroin films implanted beneath the skin and muscle of the rat.

Since the bioresorption process has a strong impact not only on the mechanical properties of the biomaterial but also on the extent of tissue regeneration, in vivo biodegradation of absorbable porous biomaterials plays a key role in tissue repair and wound healing. In the present work, porous silk fibroin films (PSFFs) were prepared by a freeze-drying method and then implanted beneath the dorsal skin and the femoral skeletal muscle of the rat. The objective was to study the rate of biodegradation of the PSFFs in different tissues, each with its distinct metabolic rate. In addition we examined the relationship between the biodegradation rate and tissue-regeneration rate semi-quantitatively by incorporating histology, microscopy and image analysis methods. Furthermore, based on our previous findings, we also explored the relationship between in vitro and in vivo rates of biodegradation. The results suggest that the PSFFs experience a similar biodegradation process regardless of the type of tissue in which they are implanted, in spite of the higher metabolic rate of the skeletal muscle. In addition, the in vitro biodegradation rate of the PSFFs was comparable to that of both skin and skeletal muscle, suggesting that an in vitro biodegradation test could be used to predict in vivo performance.

Distinct tissue responses to porous silk fibroin scaffolds (PSFSs) and polyvinyl alcohol (PVA) sponges in vivo

Selection of raw materials for biomedical materials has been one of the focuses on development of biomaterials. In this study, we used porous silk fibroin scaffolds (PSFSs) prepared by freeze drying method and polyvinyl alcohol (PVA) sponges which have similar macro-structure such as average pore size and porosity. Both materials were implanted in femoral muscles of rats, and the biocompatibility of both materials has been examined by histological observation and scoring method. Moreover, the biodegradation rates of both materials have been compared by a computer-assisted image analysis method. The results showed that PSFSs have better biocompatibility than PVA sponges in terms of deposition of collagen matrix, remodeling of extracellular matrix (ECM), infiltration of inflammatory cells, tissues formation and angiogenesis. However, PVA sponges evoked heavy and lasting infiltration of inflammatory cells, and the moderate infiltration lasted up to 23 days after the implantation. In summary, silk fibroin, as a natural protein, has incomparable biocompatibility for ECM organization and tissues formation, and thus has promising applications in tissue engineering and artificial organ.

What Is the Optimum Cover Factor

When fabricating a small diameter arterial prosthesis, the performance requirements include controlling dimensions, maintaining a uniform structure, ensuring superior mechanical properties as well as excellent biocompatibility. Material selection and fabricating methods can influence these factors. In this study, three 100% polyester prostheses, three bicomponent polyester/silk prostheses and three 100% silk prostheses were woven into seamless tubular prototype prostheses with three different basic weaves. After degumming/scouring they met the target inner diameter of 3.83 ± 0.30 mm which demonstrates that weaving is a precise and accurate way to manufacture small caliber arterial prostheses. In conclusion, the woven samples had a uniform wall structure along their strength and a range of low water permeability values and probe bursting strengths depending on their cover factor.

Preliminary numerical simulation of pulsatile flow in aortic arch with left subciavian artery

In this paper, the preliminary numerical simulation of pulsatile flow in aortic arch with left subciavian artery was conducted by the software ANSYS based on the finite element method. In order to facilitate a preliminary study, the geometric model of aortic arch with left subciavian artery was simplified as a bent pipe of 30mm in diameter with a curved-shape branch pipe. The curved-shape branch vessel is associated with the human physiological pulsatile flow in this study to address the questions about blood flow. An average blood flow rate is established according to the physiological pulsatile flow condition. The pulsatile flow in a 3-D curved-shape branch vessel is simulated numerically with the flow function, and then make general postprocessor, the distributions of velocity, pressure and wall shear on different time of the cardiac cycle are obtained.

Research on the Manufacture of Tapered Artificial Vascular

The design principle and manufacture of the new tapered artificial vascular was introduced. The idea of combining of special fan-shaped reed and lifting devices of front rest was proposed. The hardware of rigid rapier sampling weaving machine was modified to meet the request of the tapered artificial vascular weaving. It was verified through weaving a tapered artificial vascular and confirmed that the modificated equipment is successful and effective.