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At least 811 records · Page 45Linked to original sources
PubMed2004

Accessibility of N-acyl-D-mannosamines to N-acetyl-D-neuraminic acid aldolase.

N-Acetyl-D-neuraminic acid (NeuNAc) aldolase is an important enzyme for the metabolic engineering of cell-surface NeuNAc using chemically modified D-mannosamines. To explore the optimal substrates for this application, eight N-acyl derivatives of D-mannosamine were prepared, and their accessibility to NeuNAc aldolase was quantitatively investigated. The N-propionyl-, N-butanoyl-, N-iso-butanoyl-, N-pivaloyl-, and N-phenylacetyl-D-mannosamines proved to be as good substrates as, or even better than, the natural N-acetyl-D-mannosamine, while the N-trifluoropropionyl and benzoyl derivatives were poor. It was proposed that the electronic effects might have a significant influence on the enzymatic aldol condensation reaction of D-mannosamine derivatives, with electron-deficient acyl groups having a negative impact. The results suggest that N-propionyl-, N-butanoyl-, N-iso-butanoyl-, and N-phenylacetyl-D-mannosamines may be employed to bioengineer NeuNAc on cells.

Carbohydrate Conformation↗
PubMed2006

A new software tool for 3D motion analyses of the musculo-skeletal system.

BACKGROUND: Many clinical and biomechanical research studies, particularly in orthopaedics, nowadays involve forms of movement analysis. Gait analysis, video-fluoroscopy of joint replacement, pre-operative planning, surgical navigation, and standard radiostereometry would require tools for easy access to three-dimensional graphical representations of rigid segment motion. Relevant data from this variety of sources need to be organised in structured forms. Registration, integration, and synchronisation of segment position data are additional necessities. With this aim, the present work exploits the features of a software tool recently developed within a EU-funded project ('Multimod') in a series of different research studies. METHODS: Standard and advanced gait analysis on a normal subject, in vivo fluoroscopy-based three-dimensional motion of a replaced knee joint, patellar and ligament tracking on a knee specimen by a surgical navigation system, stem-to-femur migration pattern on a patient operated on total hip replacement, were analysed with standard techniques and all represented by this innovative software tool. Segment pose data were eventually obtained from these different techniques, and were successfully imported and organised in a hierarchical tree within the tool. FINDINGS: Skeletal bony segments, prosthesis component models and ligament links were registered successfully to corresponding marker position data for effective three-dimensional animations. These were shown in various combinations, in different views, from different perspectives, according to possible specific research interests. INTERPRETATION: Bioengineering and medical professionals would be much facilitated in the interpretation of the motion analysis measurements necessary in their research fields, and would benefit therefore from this software tool.

Aged↗
PubMed2005

Advanced multimodal visualisation of clinical gait and fluoroscopy analyses in the assessment of total knee replacement.

Traditional gait and fluoroscopy analysis of human movement are largely utilised but are still limited in registration, integration, synchronisation and visualisation capabilities. The present work exploits the features of a recently developed software tool based on multimodal display (Data Manager developed within the EU-funded project 'Multimod') in an exemplary clinical case. Standard lower limb gait analysis, comprising segment position, ground reaction force and EMG data collection, and three-dimensional fluoroscopy analysis at the replaced joint were performed in a total knee replacement patient while ascending stairs. Clinical information such as X-rays and standard scores were also available. Data Manager was able to import all this variety of data and to structure these in an original hierarchical tree. Bone and prosthesis component models were registered to corresponding marker position data for effective three-dimensional animations. These were also synchronised with corresponding standard video sequences. Animations, video, time-histories of collected and also processed data were shown in various combinations, according to specific interests of the bioengineering and medical professionals expected to observe and to interpret this large amount of data. This software tool demonstrated to be a valuable means to enhance representation and interpretation of measurements coming from human motion analysis. In a single software, a thorough and effective clinical and biomechanical analysis of human motion was performed.

Arthroplasty, Replacement, Knee↗
PubMed2006

Depth-of-focus: control system implications.

The depth-of-focus (DOF) plays a major role in accommodative control. It provides a neurological tolerance for retinal defocus and the perception of blur. Hence, the DOF has been an important component in bioengineering models of the accommodative system, but with its model-based control function limited to the fovea. However, new studies have demonstrated the influence of the near retinal periphery on the DOF: with increased target extent, the DOF increases. Thus, the blur control derived from the combined fovea and near retinal periphery should be incorporated into future models of accommodation.

Accommodation, Ocular↗
PubMed2006

Advances in optical detection strategies for reporter signal measurements.

Many recent advances in bioreporter technology focus on challenges related to bioengineering, yet in many applications implementation of optical signal measurement is equally susceptible to improvement. For bioluminescent bioreporters, one area of effort lies in the development of semiconductor chip-based detector modules; this holds great promise for ultra-compact and field-deployable instrumentation, but has not yet had a palpable impact on improved detection limits. Regarding lower detection limits, single-molecule detection techniques have seen their first application to bioreporters, and preliminary results serve as an indication of future promise. Another technique applicable to fluorescent bioreporters is fluorescence flow cytometry, which is rapid, suitable for high-throughput screening, and lends itself to increased analytical specificity through simple algorithmic approaches to data treatment.

Biosensing Techniques↗
PubMed2006

Collagen-containing fillers: alone and in combination.

Soft tissue fillers may be injected into facial skin to ameliorate the appearance of fine lines and wrinkles, to augment lips and hollow cheeks, and to correct other imperfections, ultimately producing a more youthful appearance. Animal- and human-derived collagen implants have been used successfully for soft tissue augmentation for several years. Bovine collagen fillers were the most popular injectable implants for nearly 2 decades in the United States. Although these are still used, human bioengineered collagen products and fillers that contain hyaluronic acid have become available and are now more commonly used than the bovine-derived products. This article discusses the rationale for using the various types of fillers in combination and describes techniques for combining these fillers.

Collagen↗
PubMed2026

Design, expression, purification, and application of novel recombinant miR-491 molecules to define the biogenesis and function of miR-491-3p versus -5p in posttranscriptional regulation of UDP-glucuronosyltransferase 1A1.

Interindividual variations in drug metabolism involve various factors, including posttranscriptional gene regulation mechanisms controlled by microRNAs (miRNAs or miRs) derived from the genome. The aim of this study was to use RNA bioengineering technology to produce novel recombinant human miR-491-5p, miR-491-3p, and pre-miR-491 molecules, namely BioRNA/miR-491-5p, BioRNA/miR-491-3p, and BioRNA/pre-miR-491, respectively, and define their functional difference in regulating UDP-glucuronosyltransferase 1A1 (UGT1A1) expression and drug-metabolizing capacity. All 6 BioRNAs were heterologously overexpressed in Escherichia coli (>30% of total RNA) and isolated by fast protein liquid chromatography to high purity (>97%). As BioRNA/pre-miR-491 agents were processed to both 5p and 3p strands in Hep3B and HepG2 cells, BioRNA/miR-491-5p and -3p were selectively processed to 5p and 3p, respectively, and each accumulated to greater levels. Immunoblotting and immunofluorescence studies demonstrated the efficacy of BioRNA/miR-491-3p to suppress UGT1A1 protein levels in Hep3B and HepG2 cells, localized on the endoplasmic reticulum, exhibiting monomeric (∼55 kDa) and oligomeric (∼150 kDa) bands under different conditions, whereas BioRNA/pre-miR-491 and miR-491-5p had no effects. Using a fluorescent substrate, N-butyl-4-(4-hydroxyphenyl)-1,8-naphthalimide, lower UGT1A1 drug-metabolizing capacities were found in cells treated with BioRNA/miR-491-3p. In addition, liquid chromatography-tandem mass spectrometry analysis revealed a 45% reduction of estradiol 3-glucuronidation activity by BioRNA/miR-491-3p in Hep3B cells, whereas formation of estradiol 17-glucuronidation mediated by other UGTs was unchanged. Together, these results underline the role of miR-491-3p in regulating UGT1A1 and its impact on cellular drug-metabolizing capacity while demonstrating the applications of recombinant miRNA agents to delineating the importance of posttranscriptional gene regulation in drug metabolism. SIGNIFICANT STATEMENT: Research on posttranscriptional gene regulation mainly uses miRNA mimics chemically synthesized in vitro. This study successfully produced 6 novel recombinant miR-491 molecules through in vivo fermentation with transfer RNA scaffold and transfer RNA-fused pre-miRNA carrier-based technologies, which were further utilized to delineate the biogenesis and function of miR-491-3p versus -5p in modulating UDP-glucuronosyltransferase 1A1 protein levels and drug-metabolizing capacity. The findings demonstrate the role of miR-491-3p in regulating UDP-glucuronosyltransferase 1A1 and value of recombinant miRNA agents for studying drug metabolism.

Humans↗
PubMed2006

Vitronectin supports migratory responses of corneal epithelial cells to substrate bound IGF-I and HGF, and facilitates serum-free cultivation.

Vitronectin (VN) is a multi-functional glycoprotein best known for its effects on cell attachment and spreading, but has more recently been shown to mediate cellular responses to growth factors. The presence of VN within the tear film and expression of required receptors (alpha v integrins) on corneal epithelial cells suggests the potential for a similar role within the ocular surface. Thus we have studied the ability of VN to alter the metabolic (MTT assay) and migratory (trans-membrane migration) responses of corneal epithelial cells to growth factors associated with the ocular surface including epidermal growth factor (EGF), hepatocyte growth factor (HGF), keratinocyte growth factor (KGF) and insulin-like growth factor-I (IGF-I). Our hypothesis was that culture surfaces coated with VN might selectively facilitate responses to growth factors which are known to bind VN including EGF, IGF-I (via IGF binding protein) and HGF. Metabolic responses were observed towards each growth factor when applied to the culture medium, but not towards culture plastic pre-treated with VN and, or growth factors. Optimal metabolic responses were observed towards IGF-I applied in conjunction with EGF. Migration through porous polycarbonate membrane was significantly increased when the substrate had been pre-coated with VN and IGF-I (applied in conjunction with IGFBP-3) or VN and HGF. This finding is consistent with the ability of IGF-I (via an IGFBP) and HGF to form complexes with VN and suggests that integrin/growth factor receptor co-activation is required for corneal epithelial cell migration. In further studies, VN applied in conjunction with IGF-I, IGFBP-3 and EGF (both to the culture plastic and in the culture medium) was found to support the establishment and serial propagation of limbal-corneal epithelial cell cultures in the absence of serum, but irradiated 3T3 cells (i3T3) were still necessary for culture expansion. Immunocytochemistry of resulting cultures for keratin 3 and p63 revealed a similar phenotype to those established under current best-practice conditions (i3T3, foetal bovine serum, EGF and insulin). In conclusion, our novel findings suggest a role for VN-growth factor complexes in stimulating corneal epithelial migration within the provisional wound bed and demonstrate that VN-growth factors interactions can be exploited to enable manufacture of bioengineered ocular surface tissue under serum-free conditions.

Cell Culture Techniques↗
PubMed2026

Optimizing focal vibration therapy for balance and gait: A systematic review.

OBJECTIVE: This systematic review evaluated the efficacy of focal (localized) vibration therapy (FVT) applied to muscles/tendons on balance, gait, and mobility, with a specific focus on defining optimal vibration protocols (frequency, amplitude, dosing) and muscle-targeting strategies to maximize sensorimotor recovery. METHODS: A systematic review was conducted across six databases (CINHAL, Embase, Medline, Web of Science, Scopus, CENTRAL) from January 2000 to May 2025. Studies were included if they involved human participants, applied FVT therapeutically, and reported balance, gait, or mobility outcomes. Data extraction included study characteristics, intervention protocols, and outcomes. Methodological quality was assessed using the PEDro scale. RESULTS: Sixty-two studies (n = 2090 participants) were included. Methodological quality assessment (PEDro scale) indicated 44% of studies met high-quality standards. Biomechanical analysis identified the quadriceps, gastrocnemius/soleus, and plantar muscles as the most effective vibration sites, given their critical roles in gait propulsion and postural stability. The synthesis of protocol data indicated a promising therapeutic window characterized by a vibration frequency of 80-120 Hz (primarily fixed sinusoidal waveforms at a single frequency) and an amplitude of 0.2-0.5 mm (reported only in 12 studies; amplitude was not reported in 23 studies), applied bilaterally for a minimum of 3 sessions per week over 4-12 weeks, which could lead to improved balance and gait performance with benefits sustained for up to 5 months. CONCLUSION: FVT shows potential to improve gait and balance, particularly when targeting lower-extremity muscles with optimized vibration parameters. To advance the field, future research must prioritize the development of standardized protocols and investigate neurophysiological mechanisms to refine FVT as a precision bioengineering solution for mobility deficits.

Humans↗
PubMed2005

Microfabricated drug delivery devices.

We review newest developments in the design and fabrication of drug delivery devices based on micropatterned structures. Electronic devices have now reached a stage of dimensions comparable to those of biological macromolecules. This raises exciting possibilities for combining microelectronics and biotechnology to develop new technologies with unprecedented power and versatility. While molecular electronics use the unique self-assembly, switching and dynamic capabilities of molecules to miniaturize electronic devices, nanoscale biosystems use the power of microelectronics to design ultrafast/ultrasmall biocompatible devices, including implants, that can revolutionize the field of bioengineering. Thus, in recent years we have seen an explosion in the field of novel microfabricated and nanofabricated devices for drug delivery. Such devices seek to develop a platform of well controlled functions in the micro- or nano-level. They include nanoparticulate systems, recognitive molecular systems, biosensing devices, and microfabricated and microelectronic devices.

Biocompatible Materials↗
PubMed2006

Interventional atrial septal defect closure using a totally bioresorbable occluder matrix: development and preclinical evaluation of the BioSTAR device.

OBJECTIVES: We sought to test the hypothesis that interventional atrial septal defect (ASD) closure can be performed safely and effectively using a bioresorbable occluder matrix. BACKGROUND: The ideal septal occluder scaffold should promote the healthiest and most complete healing response while eventually facilitating the full resorption of the material and leaving "native" tissue behind, thus minimizing the potential for future complications from chronic foreign body and maintaining the possibility for later unobstructed transseptal access to the left atrium. METHODS: The STARFlex occluders (NMT Medical Inc., Boston, Massachusetts) were modified by substituting the conventional polyester fabric for a bioengineered, acellular type-I collagen matrix derived from porcine submucosa with a heparin-coated surface (BioSTAR occluder, NMT Medical Inc.). Comparative transcatheter closure of ASDs was performed in young sheep (n = 36). Gross pathology and histopathology were obtained after follow-up periods ranging from 7 days to 2 years. RESULTS: The STARFlex (control) devices were encapsulated time-dependently by ingrown fibrous tissue. Histology showed a mild but chronically persisting foreign body reaction. By contrast, BioSTAR devices exhibited a mild-to-moderate transient cellular immune response. Heparin coating of the BioSTAR surface improved the biocompatibility of the device by reducing surface thrombogencity. A remodeling process of the collagen scaffold, starting after 30 days in vivo, resulted in the full replacement of the matrix by host tissue after 2 years of follow-up. CONCLUSIONS: The BioSTAR device is the first septal occluder with a totally bioresorbable matrix that is fully replaced by host tissue during the healing process. The promising results of this study support testing of the BioSTAR device in clinical trials.

Absorbable Implants↗
PubMed2006

Intracellular osmotic gradient generation in rat ventricle myocyte by using a micro-perfusion system.

This experimental study describes the fabrication and analysis of a micro-perfusion system that can be used in many bioengineering experiments to create rapid, large regional intracellular changes within single ventricular myocytes. The myocyte was a kind of osmometer since the cell volume was found to be strongly dependent on the perfusion solution osmolarity. This volume change was measured, indirectly, by measuring the cell width change using video-microscopy and image analysis software. Jacob's equation was used to model these results successfully. Some dual perfusion experiments to see the effects of the localized perfusion of different osmotic solutions to generate an osmotic gradient inside myocytes were also investigated. This device can be useful for studying the effects of localized pH or osmotic gradients inside myocytes, estimating intracellular ion diffusion rates, and inducing regional changes in other important intracellular ions.

Animals↗
PubMed2006

Biomedical informatics training at Stanford in the 21st century.

The Stanford Biomedical Informatics training program began with a focus on clinical informatics, and has now evolved into a general program of biomedical informatics training, including clinical informatics, bioinformatics and imaging informatics. The program offers PhD, MS, distance MS, certificate programs, and is now affiliated with an undergraduate major in biomedical computation. Current dynamics include (1) increased activity in informatics within other training programs in biology and the information sciences (2) increased desire among informatics students to gain laboratory experience, (3) increased demand for computational collaboration among biomedical researchers, and (4) interaction with the newly formed Department of Bioengineering at Stanford University. The core focus on research training-the development and application of novel informatics methods for biomedical research-keeps the program centered in the midst of this period of growth and diversification.

Biomedical Engineering↗
PubMed2005

Ultrasonic measurement of depth-dependent transient behaviors of articular cartilage under compression.

We previously reported an ultrasound method for measuring the depth-dependent equilibrium mechanical properties of articular cartilage using quasi-static compression. The objective of this paper was to introduce our recent development for nondestructively measuring the transient depth-dependent strains of full-thickness articular cartilage specimens prepared from bovine patellae. A 50 MHz focused ultrasound transducer was used to collect ultrasound echoes from articular cartilage specimens (n=8) and sponge phantoms with open pores (n=10) during tests of compression and subsequent stress-relaxation. The transient displacements of the tissues at different depths along the compression direction were calculated from the ultrasound echoes using a cross-correlation tracking technique. An LVDT sensor and a load cell were used to measure the overall deformation of the tissue and the applied force, respectively. Results showed that the tissues inside the cartilage layer continued to move during the stress-relaxation phase after the compression was completed. In the equilibrium state, the displacements of the cartilage tissues at the depths of 1/4, 1/2, and 3/4 of the full-thickness reduced by 51%+/-22%, 54%+/-17%, and 50+/-17%, respectively, in comparison with its peak value. However, no similar phenomenon was observed in the sponge phantoms. Our preliminary results demonstrated that this ultrasound method may provide a potential tool for the nondestructive measurement of the transient depth-dependent processes involved in biological and bioengineered soft tissues as well as soft biomaterials under dynamic loading.

Animals↗
PubMed2004

Strain distribution in an elastic substrate vibrated in a bioreactor for vocal fold tissue engineering.

A bioreactor previously described was used to quantify the shear strain along a bioengineered tissue scaffold driven at low audio frequencies (20-200 Hz). Standing wave patterns were calculated analytically by solving a classical boundary value problem for a vibrating string under tension and bending stiffness. Boundary conditions were non-traditional in that small pivot arms at the endpoints allowed neither the displacement nor the velocity to go to zero. The calculations were corroborated with stroboscopic measurement of the motion of the material in the bioreactor. Results indicate that shear strains up to 0.2 can be obtained at low frequencies (20 Hz), with a gradual decrease at higher frequencies due to the decaying amplitude response of the mechanical driver. The bioreactor may be useful for approximating the Young's modulus of the material in situ by probing for resonance frequencies in the standing wave pattern. A yet unsolved problem is a variable drag coefficient along the length of the material due to fluid turbulence in the culture medium.

Bioartificial Organs↗
PubMed2005

In vivo age- and sex-related creep of human lumbar motion segments and discs in pure centric tension.

In vivo creep of human lumbar motion segments and discs subject to pure centric tension is presented, in terms of aging, sex and disc level. Time-related elongations of segments L3-4, L4-5 and L5-S1 were measured during the usual 20 min long traction hydrotherapy of patients, by using a computerized subaqual ultrasound measuring method [Kurutz et al., 2002a. Orvosi Hetilap 143 (13), 673-684; Kurutz et al., 2003. Journal of Bioengineering and Biomechanics 5 (1), 67-92]. Elongation of segments was considered as a change of the distance between two adjacent spinous processes. Based on these experiments, in vivo creep of human lumbar FSUs was investigated in centric tension, in terms of sex, age and disc level. Three-parameter rheological models were used to determine viscoelastic tensile moduli of human lumbar FSUs and discs. From three time-related measured elongation values, in vivo damping constants with creep functions were calculated for each segment, in terms of sex, aging and disc level. It has been demonstrated that initial elastic elongations decrease, concerning stiffness increase with aging. Similarly, tensile creep elongations decrease, damping properties increase with aging. Former observations concerning the difference in deformation propagation of men and women in time, have been verified by means of creep analysis: although males have higher initial elastic deformability, due to a smaller damping of females, the deformation propagation of women overtakes men in creep process. This tendency is more significant with aging. Increasing damping was observed in distal direction, both for males and females.

Age Factors↗
PubMed2004

Spectral analysis and fingerprinting for biomedia characterisation.

Classical culture media, as well as domestic and/or industrial wastewater treated by biological processes, have a complex composition. The on-line and/or in situ determination of some substances is possible, but expensive, as sample collection and pre-treatment are often necessary with strict rules of sterility. More global methods can be used to detect rapidly "accidents" such as the appearance of an undesirable by-product in a fermentation broth or of a toxic substance in wastewater. These methods combine a "hard" part, for sensing, and a "soft" part, for data treatment. Among potential "hard" candidates, spectroscopy can be the basis for non-invasive and non-destructive measuring systems. Some of them have been already tested in situ: ultra-violet-visible, infra-red (mid or near), fluorescence (mono-dimensional, two-dimensional or synchronous), dielectric, while others, more sophisticated, such as mass spectrometry, coupled or not to pyrolysis, nuclear magnetic resonance and Raman spectroscopy, have been proposed. All these methods provide spectra, i.e. large sets of data, from which meaningful information should be rapidly extracted, either for analysis or fingerprinting. The recourse to data-mining techniques (the "soft" part) such as principal components analysis, projection on latent structures or artificial neural networks, is a necessary step for that task. A review of techniques, mostly based on spectroscopy, with examples taken in the bioengineering field in general is proposed.

Biotechnology↗
PubMed2006

Clinical applications of high-density surface EMG: a systematic review.

High density-surface EMG (HD-sEMG) is a non-invasive technique to measure electrical muscle activity with multiple (more than two) closely spaced electrodes overlying a restricted area of the skin. Besides temporal activity HD-sEMG also allows spatial EMG activity to be recorded, thus expanding the possibilities to detect new muscle characteristics. Especially muscle fiber conduction velocity (MFCV) measurements and the evaluation of single motor unit (MU) characteristics come into view. This systematic review of the literature evaluates the clinical applications of HD-sEMG. Although beyond the scope of the present review, the search yielded a large number of "non-clinical" papers demonstrating that a considerable amount of work has been done and that significant technical progress has been made concerning the feasibility and optimization of HD-sEMG techniques. Twenty-nine clinical studies and four reviews of clinical applications of HD-sEMG were considered. The clinical studies concerned muscle fatigue, motor neuron diseases (MND), neuropathies, myopathies (mainly in patients with channelopathies), spontaneous muscle activity and MU firing rates. In principle, HD-sEMG allows pathological changes at the MU level to be detected, especially changes in neurogenic disorders and channelopathies. We additionally discuss several bioengineering aspects and future clinical applications of the technique and provide recommendations for further development and implementation of HD-sEMG as a clinical diagnostic tool.

Electromyography↗