Hybrid Additive Microfabrication Scaffold Incorporated with Highly Aligned Nanofibers for Musculoskeletal Tissues

BACKGROUND: Latest tissue engineering strategies for musculoskeletal tissues regeneration focus on creating a biomimetic microenvironment closely resembling the natural topology of extracellular matrix. This paper presents a novel musculoskeletal tissue scaffold fabricated by hybrid additive manufacturing method. METHODS: The skeleton of the scaffold was 3D printed by fused deposition modeling, and a layer of random or aligned polycaprolactone nanofibers were embedded between two frames. A parametric study was performed to investigate the effects of process parameters on nanofiber morphology. A compression test was performed to study the mechanical properties of the scaffold. Human fibroblast cells were cultured in the scaffold for 7 days to evaluate the effect of scaffold microstructure on cell growth. RESULTS: The tip-to-collector distance showed a positive correlation with the fiber alignment, and the electrospinning time showed a negative correlation with the fiber density. With reinforced nanofibers, the hybrid scaffold demonstrated superior compression strength compared to conventional 3D-printed scaffold. The hybrid scaffold with aligned nanofibers led to higher cell attachment and proliferation rates, and a directional cell organization. In addition, there was a nonlinear relationship between the fiber diameter/density and the cell actinfilament density. CONCLUSION: This hybrid biofabrication process can be established as a highly efficient and scalable platform to fabricate biomimetic scaffolds with patterned fibrous microstructure, and will facilitate future development of clinical solutions for musculoskeletal tissue regeneration.

Implantable Bladder Sensors: A Methodological Review / 대한배뇨장애요실금학회지

The loss of urinary bladder control/sensation, also known as urinary incontinence (UI), is a common clinical problem in autistic children, diabetics, and the elderly. UI not only causes discomfort for patients but may also lead to kidney failure, infections, and even death. The increase of bladder urine volume/pressure above normal ranges without sensation of UI patients necessitates the need for bladder sensors. Currently, a catheter-based sensor is introduced directly through the urethra into the bladder to measure pressure variations. Unfortunately, this method is inaccurate because measurement is affected by disturbances in catheter lines as well as delays in response time owing to the inertia of urine inside the bladder. Moreover, this technique can cause infection during prolonged use; hence, it is only suitable for short-term measurement. Development of discrete wireless implantable sensors to measure bladder volume/pressure would allow for long-term monitoring within the bladder, while maintaining the patient's quality of life. With the recent advances in microfabrication, the size of implantable bladder sensors has been significantly reduced. However, microfabricated sensors face hostility from the bladder environment and require surgical intervention for implantation inside the bladder. Here, we explore the various types of implantable bladder sensors and current efforts to solve issues like hermeticity, biocompatibility, drift, telemetry, power, and compatibility issues with popular imaging tools such as computed tomography and magnetic resonance imaging. We also discuss some possible improvements/emerging trends in the design of an implantable bladder sensor.

Tissue development and construction and its regulational mechanism / 生物医学工程学杂志

From the perspective of Regenerative Medicine, the tissue generated in vitro can imitate the physiological and pathological tissue to a certain extent. However, the structures and functions of the in vitro tissue are very simple so that research on in vitro self-assembling and imitating of tissue development is necessary. The development of Nanotechnology and the technology of micro-structure makes the in vitro tissue assembling possible. As previous studies showed that, besides genetic material, tissue architecture and its micro-environment are closely related to morphogenesis of in vitro tissue. Thus, how to design and assemble microstructure to make the tissue molding still requires effort. How to predict and control the development mechanism in vitro is also a question needed to be resolved. In this essay, we reviewed the mechanism of assembling and imitating of in vitro tissue based on the theory of physics, biology and systemic integrated structure.

The sub-microsecond pulser applied for electroporation effect / 生物医学工程学杂志

A sub-microsecond pulse generation applied for electroporation effects of tumor cell is presented in this paper. The principle of the generator is that the expected pulse waveform is intercepted from the RC discharge curve by controlling the on-off states of two IGBT modules with a synchronous controller. Experimental tests indicate that the generator can produce adjustable pulse waveform parameters with 0.5-3.5kV amplitude, 300-800 ns pulse duration, 1-400Hz repetition frequency rate, and it is suitable for the study of the electroporation effect experiments.

Bioactivity of micro/nanostructural layers on titanium surfaces / 生物医学工程学杂志

Porous surfaces have an important effect on bioactivity of titanium implants. In this study, two micro/nanostructural titanium surfaces were prepared by chemical and electrochemical method. The two samples had different diameters of nanotubes. Tests of biomineralization and codeposition in simulated body fluid and bovine serum albumin (BSA) were carried out in order to evaluate the bioactivity of micro/nanostructural titanium surfaces. The information of the surfaces was detected using scanning electron microscope and X-ray diffractometer. The results showed that the bioactivity of micro/nanostructural titanium increased with the diameter of nanotubes. Furthermore, the existence of BSA can accelerate biomineralization and decrease the crystallinity of hydroxyapatite coating.

Development of a New Blood Typing Kit Using the Microfluidics Separation Technique / 대한혈액학회지

BACKGROUND: Blood typing is an essential test for transfusion. Generally, blood typing is performed using a slide test, tube test or microcolumn agglutination test. The aims of this study were to develop a new blood typing kit using micromachining, microfluidics and microseparation methods, and to evaluate the clinical usefulness of the new blood typing kit. METHODS: We designed and manufactured a blood typing microchip using polydimethylsiloxane (PDMS), which contained a microchannel (25~200 micrometer). The blood sample and antisera to be tested were dropped on the microwell for movement and mixing by capillary action. Once agglutination occurred, the microchannel acts as a filter and the blood type was determined by observation by the naked eye. To evaluate the newtyping kit, we tested sensitivity using artificially diluted blood and compared the results of the new typing method with the slide and tube methods using 70 samples. RESULTS: The new blood typing kit could differentiate a +4~+2 agglutination reaction, but could not detect a +1 agglutination reaction as observed by the naked eye. Among 70 samples, the results of ABO and Rh typing by the new typing method (n=66, > or = +2 agglutination reaction by the column agglutination method) were in accord with the results of the tube and slide methods, but couldnot detect agglutination in all 4 clinical samples, below a +1 agglutination reaction. CONCLUSION: The new blood typing kit is inadequate for routine use in the clinical laboratory due to low sensitivity, but with further improvement, it can be used economically, conveniently and objectively for blood typing without any special equipment. Moreover, the microfludics and separation method may be broadly applicable in other tests using the hemagglutination method.

Measurement of Smooth Muscle Cell Migration on the Micromachined Groove Topology

PURPOSE: The spreading, orientation, and chemotaxis with the gradient of a chemoattractant of smooth muscle cells (SMCs) were studied on the micro-grooved substrata by the light, fluorescence and scanning electron microscopy. METHOD: Vertical-walled grooves were produced in silicon wafers by the micromachining technique. All grooves were 4~20micrometer deep and 10~80 micrometer wide. SMCs were cultured on each microgroove and examined under stereo-microscope. RESULT: Cell clusters were markedly oriented by all the grooved substrata examined. Time-lapse images acquired from CCD (Charge Coupled Device) showed that the grooves directed the migration of SMCs. There was no prominent difference in the migration speed of SMCs according to the grooves. All the cytoskeletal fibers were reorganized in the same direction with grooves. Especially the alignments of microtubule and intermediate filaments were distinguished in the SMCs on the micro grooves. CONCLUSION: These results could be applied to the analysis of vascular restenosis and the development of artificial blood vessels.