Biomedical Engineering: Applications, Basis and Communications

Polymeric scaffolds, in the form of porous membranes, modified to favour cell adhesion and proliferation on their surface, were prepared using an innovative technique of functionalization, based on molecularly imprinting technology.

A series of membranes based on poly-ε-caprolactone were obtained through phase inversion using different solvents and non-solvents. Diffusion tests showed that prepared membranes exhibited a good permeability towards important nutrients such as folic acid and glucose. The ability of membranes, modified with imprinted nanoparticles, to facilitate cell adhesion and proliferation was evaluated by cell culture method using murine fibroblast cell line. SEM analysis at 72 h after seeding revealed an improved cell distribution on the surface of the membranes functionalized by deposition of molecularly imprinted nanoparticles.

In some cases, different brain regions give rise to strongly-coherent electrical neural activities. For example, pure tone evoked activations of the bilateral auditory cortices exhibit strong coherence. Conventional 2nd order statistics-based spatio-temporal algorithms, such as MUSIC (MUltiple SIgnal Classification) and beamforming encounter difficulties in localizing such activities. In this paper, we proposed a novel solution for this case. The key idea is to map the measurement data into a new data space through a transformation prior to the localization. The orthogonal complement of the lead field matrix for the region to be suppressed is generated as the transformation matrix. Using a priori knowledge or another independent imaging method, such as sLORETA (standard LOw REsolution brain electromagnetic TomogrAphy), the coherent source regions can be primarily identified. And then, in the transformed data space a conventional spatio-temporal method, such as MUSIC, can be used to accomplish the localization of the remaining coherent sources. Repeatedly applying the method will achieve localization of all the coherent sources. The algorithm was validated by simulation experiments as well as by the reconstructions of real bilateral auditory cortical coherent activities.

The stimulative effects and the associated mechanism of low-intensity ultrasound on endothelial cells were investigated in this study. Human umbilical cord endothelial cells (HUVECs) were exposed to 1 MHz pulsed ultrasound at 34 mW/cm² for 10 min daily. The cell proliferation, nitric oxide release, intracellular calcium concentration, and endothelial nitric oxide synthase (eNOS) gene and protein expressions after ultrasound exposure were analyzed. It was found that ultrasound exposure did not change the cell proliferation, but it enhanced the release of nitric oxide and Ca²⁺ ions, and increased the eNOS activity. The induced phosphorylation of eNOS (Ser¹¹⁷⁷) by the ultrasound exposure was inhibited by the addition of N-[2-(p-bromocinnamylamino) ethyl]-5-isoquinoline sulfonamide (H89, a protein kinase A inhibitor), but not 2-(4-morpholino)-8-phenyl-4H-1-benzopyran-4-one hydrochloride (LY294002, a phosphoatidylinositol 3-kinase inhibitor). The induced phosphorylation of Akt (protein kinase B, Ser⁴⁷³) by the ultrasound exposure was inhibited by the addition of LY294002, but not by the presence of H89. The results also applied to bovine carotid artery endothelial cells (BAECs) exposed to ultrasound at a larger intensity (68 mW/cm²). The above experiments suggested that low-intensity ultrasound may promote eNOS activity of endothelial cells via the phosphatidylinositol 3-kinase/Akt/protein kinase A signaling pathway. This may have implications on the therapeutic effect of ultrasound in tissue repair.

Currently, all the data processing strategies for functional magnetic resonance imaging (fMRI) utilize temporal informationpaying little attention to or totally ignoring frequency information. In this paper, a new method is proposed to detect the functional activation regions in the brain by using the frequency information of fMRI time series. The main idea is that the frequency entropy information (FEI) difference of fMRI data between task and control states is specified as brain activation index. The validity of the proposed FEI approach is confirmed by analyzing the result of the simulated synthesized data. Additionally, the comparison of receiver operating characteristic (ROC) curves acquired respectively from the proposed scheme, the statistical parametric mapping (SPM), and the Support Vector Machine (SVM) methods of fMRI data analysis indicate an obvious superiority of the former. In vivo fMRI studies of subjects with event-related experiment reveal that FEI method can enable the effective detection of brain functional activation.

The B-factor, which is also known as temperature factor or Debby–Waller factor, is an important structural flexibility index of the ground-state protein conformation. In particular, the B-factors associated with a segment of residues, reflect the local flexibility of the corresponding protein tertiary substructure. Recent studies have shown that, for certain families of proteins, there exists a high-degree of correlation between the B-factors and the protein functional sites, including antigenic regions, enzyme active sites, and nucleotide binding sites. This paper presents a sequence–based predictor of B-factors with a dual-model approach.

 The design of the dual-model approach has been aimed at exploiting the bi-modal distribution of B-factors in order to achieve higher prediction accuracy. In this paper, the prediction accuracy is measured by Pearson correlation coefficient. Experimental results show that the dual-model predictor proposed in this article is capable of delivering superior correlation coefficient in comparison with two predictors reported in two latest papers.

 Though experimental results show that the dual-model proposed in this paper really works more effectively than the conventional approach, it is of interest to continue investigating more advanced designs since there exists a strong correlation between B-factors and protein functional sites. In this respect, identifying additional physiochemical properties that are related to structural flexibility deserves a high-degree of attention.

Hydrophilic Fe₃O₄ nanoparticles with a mean diameter size of 15 nm were synthesized by means of the direct reduction of FeCl₃ and FeCl₂ in an aqueous solution. The heating properties of Fe₃O₄ nanoparticles under an alternating magnetic field were investigated in a frequency range of 50–500 kHz and a magnitude range of 3.1–5.0 kA/m. To distinguish the roles of Néel and Brownian relaxation mechanisms, polydimethylsiloxane (PDMS) and water were employed as a medium, in which PDMS plays a significant role of eliminating the effect of Brownian relaxation. It is experimentally and theoretically confirmed that, for the Fe₃O₄/water system, high-specific absorption rates are due to a combination of both mechanisms, with an enhanced contribution due to Néel relaxation with increasing frequency and magnitude of the alternating electromagnetic field. The contribution efficiency of Néel relaxation increases from 36–56% by increasing the electromagnetic field frequency from 50–300 kHz, and then retains a saturated value of ~ 56% at 300–500 kHz. Moreover, a linear increase of the contribution efficiency of Néel relaxation at 300 kHz was observed from 55–65% by increasing the magnitude of electromagnetic field at 3.1–5.0 kA/m. The current research can be widely-expanded to explain the electromagnetic heating effect of other ferrofluid systems.

Injectable filler, which is often applied in minimally invasive surgery, has been widely-used in facial rejuvenation. Because of its convenience, effective usage and less downtime after treatment for the patients, it becomes one of the most popular treatment methods at present. The currently available products containing collagen base have been proven to have much satisfactory safety and effectiveness, but one of its disadvantages is the lack of long-term volume persistence. We have previously prepared the reconstituted collagen fibrils with hyaluronic acid (HA) by modifying the fibril surface. This study is to evaluate the potential of these materials as injectable filler in vitro. A preparation of collagen fibrils with a diameter of 100–150 nm was used. The modification rate of HA on the fibril surface was 20%. In assessment of the biocompatibility, it was proven that the collagen fibril and HA-collagen fibril treated with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) had no cytotoxicity or inhibitory actions. In interactions between these materials and cells, it was found that the existence of HA could improve the migration ability of L929 fibroblasts and breast cancer cells (MDA-MB 435s). In conclusion, collagen fibril and HA-collagen fibril have the potential to be developed into an injection as a soft tissue filler for biomedical applications.

Functional magnetic resonance imaging (fMRI) is widely-used for detection of the brain's neural activity. The signals and images acquired through this imaging technique demonstrate the human brain's response to pre-scheduled tasks. Several studies on blood oxygenation level-dependent (BOLD) signal responses demonstrate nonlinear behavior in response to a stimulus. In this paper we propose a new mathematical approach for modeling BOLD signal activity, which is able to model nonlinear and time variant behaviors of this physiological system. We employ the Nonlinear Auto Regressive Moving Average (NARMA) model to describe the mathematical relationship between output signals and predesigned tasks. The model parameters can be used to distinguish between rest and active states of a brain region. We applied our proposed method for active region detection on real as well as simulated data sets. The results show superior performance in comparison with existing methods.

It was generally considered that a femoral stem with a rough surface was not suitable for cemented fixation in total hip arthroplasty. The long-term follow-up studies on the cemented rough stems clearly revealed a significantly higher loosening and revision rate than those of polished stems. However, from a biomechanics point of view, a rough surface might result in stronger cement-prosthesis bonding because of micro-interlocking between the bone cement and the stem. This contradiction between biomechanical standpoint and clinical observation remains as a problem to be resolved. Thus, this study was designed to evaluate the effect of stem surface roughness and the cement pre-coating process on the bonding strength of the prosthesis-cement interface. A total of 48 Co-Cr rods with three different levels of surface roughness (polished, plasma-treated and bead-coated, 16 in each group) were enrolled in the study. All specimens were cylindrical in shape with lengths of 120 mm and 12 mm diameters. Sixteen specimens in each group were then treated with non-precoated or precoated cement fixation (8 in each group). After fixing the Co-Cr rod, the pushout test was carried out using a MTS testing machine, and the shear strength for each group was compared. An additional microscopic observation of the metal/cement interface was also performed. The results of the pushout test indicated that the shear strength increased with increasing implant surface roughness, regardless of whether or not the stem was treated with the cement precoating process. However, stem precoating did not statistically improve the bonding strength at each level of surface roughness. Microscopic observation of the stem-cement interfaces revealed that the bone cement significantly infiltrated the rough surface in both the precoated and non-precoated groups with stems with various levels of surface roughness. Surface roughness of the femoral stem significantly affected the stem/cement interface, improving shear strength significantly. Stem precoating did not statistically improve the shear strength using the present cementing technique with retrograde high-pressure injection. Although a high surface roughness of the femoral stem appears to be an effective choice to improve implant fixation in cemented THA, the longevity of the prostheses implanted with such a stem can only be determined from long-term clinical trials.

This paper, describes the biomedical testing of an Anterior Cruciate Ligament (ACL) reconstruction using an interference screw fixation on the bovine and porcine tissues. The harvesting procedure, experimental setup, mechanical testing, and evaluation of the tendon graft interference screw fixation are all presented throughout this study. A guideline has also been introduced to evaluate the basic mechanical properties of the bone components and the tendon graft.