Neural network analysis of nocturnal SpO2 signal enables easy screening of sleep apnea in patients with acute cerebrovascular disease.

Current diagnostics of sleep apnea relies on the time-consuming manual analysis of complex sleep registrations, which is impractical for routine screening in hospitalized patients with a high probability for sleep apnea, e.g. those experiencing acute stroke or transient ischemic attacks (TIA). To overcome this shortcoming, we aimed to develop a convolutional neural network (CNN) capable of estimating the severity of sleep apnea in acute stroke and TIA patients based solely on the nocturnal oxygen saturation (SpO2) signal. The CNN was trained with SpO2 signals derived from 1379 home sleep apnea tests (HSAT) of suspected sleep apnea patients and tested with SpO2 signals of 77 acute ischemic stroke or TIA patients. The CNN's performance was tested by comparing the estimated respiratory event index (REI) and oxygen desaturation index (ODI) with manually obtained values. Median estimation errors for REI and ODI in patients with stroke or TIA were 1.45 events/hour and 0.61 events/hour, respectively. Furthermore, based on estimated REI and ODI, 77.9% and 88.3% of these patients were classified into the correct sleep apnea severity categories. The sensitivity and specificity to identify sleep apnea (REI > 5 events/hour) were 91.8% and 78.6%, respectively. Moderate-to-severe sleep apnea was detected (REI > 15 events/hour) with sensitivity of 92.3% and specificity of 96.1%. The CNN analysis of the SpO2 signal has great potential as a simple screening tool for sleep apnea. This novel automatic method accurately detects sleep apnea in acute cerebrovascular disease patients and facilitates their referral for a differential diagnostic HSAT or polysomnography evaluation.

Acute stroke and TIA patients have specific polygraphic features of obstructive sleep apnea.

PURPOSE: Obstructive sleep apnea (OSA) is associated with increased risk for stroke, which is known to further impair respiratory functions. However, it is unknown whether the type and severity of respiratory events are linked to stroke or transient ischemic attack (TIA). Thus, we investigate whether the characteristics of individual respiratory events differ between patients experiencing TIA or acute ischemic stroke and matched patients with clinically suspected sleep-disordered breathing. METHODS: Polygraphic data of 77 in-patients with acute ischemic stroke (n = 49) or TIA (n = 28) were compared to age, gender, and BMI-matched patients with suspected sleep-disordered breathing and no cerebrovascular disease. Along with conventional diagnostic parameters (e.g., apnea-hypopnea index), durations and severities of individual apneas, hypopneas and desaturations were compared between the groups separately for ischemic stroke and TIA patients. RESULTS: Stroke and TIA patients had significantly shorter apneas and hypopneas (p < 0.001) compared to matched reference patients. Furthermore, stroke patients had more central apnea events (p = 0.007) and a trend for higher apnea/hypopnea number ratios (p = 0.091). The prevalence of OSA (apnea-hypopnea index ≥ 5) was 90% in acute stroke patients and 79% in transient ischemic attack patients. CONCLUSION: Stroke patients had different characteristics of respiratory events, i.e., their polygraphic phenotype of OSA differs compared to matched reference patients. The observed differences in polygraphic features might indicate that stroke and TIA patients suffer from OSA phenotype recently associated with increased cardiovascular mortality. Therefore, optimal diagnostics and treatment require routine OSA screening in patients with acute cerebrovascular disease, even without previous suspicion of OSA.

Polysomnographic scoring of sleep bruxism events is accurate even in the absence of video recording but unreliable with EMG-only setups.

PURPOSE: To determine the accuracy of scoring masticatory muscle activity (MMA) events in seven different polysomnography (PSG) setups. METHODS: Nineteen volunteers (13 females, 6 males, age 31.1 ± 12.9 years, 12 self-proclaimed bruxers) attended one-night PSG recording, supplemented with audio, video, and a separate frontal electroencephalography electrode set (FES). The same examiner scored the MMA events with seven different setups, with varying number of channels available: (1) one, (2) two, and (3) four EMG channels, (4) PSG without audio or video (PSG-N), (5) home PSG with FES and audio (FES-A), (6) PSG with audio (PSG-A), and (7) PSG with audio and video (PSG-AV). A subset (n = 10) of recordings was scored twice to determine intra-scorer reliability. MMA indices and accuracy of scoring the events in different setups were compared against PSG-AV. RESULTS: The intra-class correlation coefficient (ICC) between PSG-AV and PSG-A was high (0.940, p < 0.001) as well as for FES-A (0.927, p < 0.001), whereas for PSG-N, it was lower (0.835, p < 0.001); for setups with only EMG channels, coefficients were very low (ICC < 0.100 for all). Intra-examiner reliability was high (ICC > 0.939 for all setups), with the exception of PSG-N (ICC = 0.764, p = 0.002). When comparing against the MMA events scored in PSG-AV, the sensitivity of MMA event recognition for PSG-A was 78.5% and specificity 95.5%, which were substantially higher than sensitivity (52.0%) and specificity (87.2%) of PSG-N. CONCLUSIONS: MMA event scoring accuracy with PSG-A or FES-A is almost comparable to PSG-AV. Since precise event recognition is essential for accurate MMA scoring, it is evident that one cannot rely exclusively on EMG.

Home Polysomnography Reveals a First-Night Effect in Patients With Low Sleep Bruxism Activity.

STUDY OBJECTIVES: To examine the presence of a first-night effect (FNE) and the level of internight variability in sleep bruxism (SB) activity when a self-applicable electrode set is used in home polysomnography (PSG) in a sample of subjects with possible SB. METHODS: Fourteen females and two males aged 38.3 ± 9.1 years (mean ± standard deviation) with self-reported SB underwent home-PSG on three consecutive nights. The subjects applied PSG sensors themselves, including self-applicable electrode sets used to record sleep and masseter muscle activity. Repeated-measures analysis of variance was used to compare SB and sleep variables between the nights. RESULTS: Surprisingly, there were statistically significant elevations in the rhythmic masticatory muscle activity (RMMA) episode index (P = .009), burst index (P = .016), and bruxism time index (P = .049) throughout the course of 3 nights. More bruxers were diagnosed on the second (6 bruxers, ≥ 2 episodes/h) and third night (7 bruxers) compared to the first night (2 bruxers). Most subjects (14/16) had their highest RMMA index on the second or third night. The mean coefficient of variation for RMMA episode index was 50.7%. No statistically significant differences were detected in other sleep variables. CONCLUSIONS: The results indicate that a FNE may be present in SB activity, possibly lasting several nights in some subjects. Furthermore, FNE appears to be combined with high internight variability of SB activity without indications of internight changes in sleep macrostructure. To confirm the level of ongoing SB activity, several nights of PSG may be required, especially in subjects with low first-night SB activity. COMMENTARY: A commentary on this article appears in this issue on page 1281.

Success Rate and Technical Quality of Home Polysomnography With Self-Applicable Electrode Set in Subjects With Possible Sleep Bruxism.

Using sleep laboratory polysomnography (PSG) is restricted for the diagnosis of only the most severe sleep disorders due to its low availability and high cost. Home PSG is more affordable, but applying conventional electroencephalography (EEG) electrodes increases its overall complexity and lowers the availability. Simple, self-administered single-channel EEG monitors on the other hand suffer from poor reliability. In this study, we aimed to quantify the reliability of self-administrated home PSG recordings conducted with a newly designed ambulatory electrode set (AES) that enables multichannel EEG, electrooculography, electromyography, and electrocardiography recordings. We assessed the sleep study success rate and technical quality of the recordings performed in subjects with possible sleep bruxism (SB). Thirty-two females and five males aged 39.6 ± 11.6 years (mean±SD) with self-reported SB were recruited in the study. Self-administrated home PSG recordings with two AES designs were conducted (n = 19 and 21). The technical quality of the recordings was graded based on the proportion of interpretable data. Technical failure rate for AES (both designs) was 5% and SB was scorable for 96.9% of all recorded data. Only one recording failed due to mistakes in self-applying the AES. We found that the proportion of good quality self-administrated EEG recordings is significantly higher when multiple channels are used compared to using a single channel. Sleep study success rates and proportion of recordings with high quality interpretable data from EEG channels of AES were comparable to that of conventional home PSG. Self-applicable AES has potential to become a reliable tool for widely available home PSG.

Screen-printed ambulatory electrode set enables accurate diagnostics of sleep bruxism.

Currently, definite diagnosis of sleep bruxism requires polysomnography. However, it is restrictedly available, and too cumbersome and expensive for the purpose. The aim of this study was to introduce an ambulatory electrode set and evaluate its feasibility for more cost-effective diagnostics of sleep bruxism. Six self-assessed bruxers (one male, five females; aged 21-58 years) and six healthy controls (four males, two females, aged 21-25 years) underwent a standard polysomnographic study and a concurrent study with the ambulatory electrode set. Bruxism events, cortical arousals and sleep stages were scored for the two montages separately in a random order, and obtained sleep parameters were compared. In addition, the significance of video recording and sleep stage scoring for the diagnostic accuracy of ambulatory electrode set was determined. Ambulatory electrode set yielded similar diagnoses as standard polysomnography in all subjects. However, compared with standard polysomnography the median (interquartile range) tonic bruxism event index was significantly higher in the control group [+0.38 (+0.08 to +0.56) events per hour, P = 0.046], and the phasic bruxism event index was significantly lower in the bruxer group [-0.44 (-1.30 to +0.07) events per hour, P = 0.046]. Exclusion of video recording and both video recording and sleep stage scoring from analysis increased overestimation of the tonic bruxism event index in the control group +0.86 (+0.42 to +1.03) and +1.19 (+0.55 to +1.39) events per hour, P = 0.046 and P = 0.028, respectively], resulting in one misdiagnosed control subject. To conclude, ambulatory electrode set is a sensitive method for ambulatory diagnostics of sleep bruxism, and video recording and sleep stage scoring help reaching the highest specificity of sleep bruxism diagnostics.

Assessment of the suitability of using a forehead EEG electrode set and chin EMG electrodes for sleep staging in polysomnography.

Recently, a number of portable devices designed for full polysomnography at home have appeared. However, current scalp electrodes used for electroencephalograms are not practical for patient self-application. The aim of this study was to evaluate the suitability of recently introduced forehead electroencephalogram electrode set and supplementary chin electromyogram electrodes for sleep staging. From 31 subjects (10 male, 21 female; age 31.3 ± 11.8 years), sleep was recorded simultaneously with a forehead electroencephalogram electrode set and with a standard polysomnography setup consisting of six recommended electroencephalogram channels, two electrooculogram channels and chin electromyogram. Thereafter, two experienced specialists scored each recording twice, based on either standard polysomnography or forehead recordings. Sleep variables recorded with the forehead electroencephalogram electrode set and separate chin electromyogram electrodes were highly consistent with those obtained with the standard polysomnography. There were no statistically significant differences in total sleep time, sleep efficiency or sleep latencies. However, compared with the standard polysomnography, there was a significant increase in the amount of stage N1 and N2, and a significant reduction in stage N3 and rapid eye movement sleep. Overall, epoch-by-epoch agreement between the methods was 79.5%. Inter-scorer agreement for the forehead electroencephalogram was only slightly lower than that for standard polysomnography (76.1% versus 83.2%). Forehead electroencephalogram electrode set as supplemented with chin electromyogram electrodes may serve as a reliable and simple solution for recording total sleep time, and may be adequate for measuring sleep architecture. Because this electrode concept is well suited for patient's self-application, it may offer a significant advancement in home polysomnography.

Effect of oxygen desaturation threshold on determination of OSA severity during weight loss.

PURPOSE: Weight loss leads to improvement of obstructive sleep apnea (OSA), based on frequency of respiratory events (apnea-hypopnea index, AHI). However, AHI does not incorporate the severity of individual obstruction events. The American Academy of Sleep Medicine suggests two alternative oxygen desaturation thresholds (ODT) for scoring of hypopneas. We hypothesize that lowering the ODT level increases the determined impact of weight loss on OSA severity. We investigate this during weight change with AHI and adjusted AHI. Adjusted AHI is a novel parameter incorporating both severity and number of the events. METHODS: Ambulatory polygraphic data of 54 OSA patients (F 15/M 39, 51.7 ± 8.4 years), divided into weight loss (>5 %, n = 20), control (weight change 0-5 %, n = 26), and weight gain (>5 %, n = 8) groups, were evaluated at baseline and after 5-year follow-up. Effect of ODT (ODT2%-ODT6%) on AHI and adjusted AHI was investigated. RESULTS: The greatest changes in AHI (decrease in weight loss group and increase in weight gain group) were observed with ODT2%. Changes in AHI diminished with increasing ODT. In weight loss group, adjusted AHI showed a similar but non-significant trend. In contrast, the higher ODT was used in weight gain group, the greater increase in adjusted AHI resulted. Using adjusted AHI instead of AHI, led to a smaller number of patients (20 vs. 55 %, ODT3%) whose OSA severity category improved along weight loss. CONCLUSIONS: Weight loss significantly reduced AHI. This reduction was highly dependent on selected ODT. The change in adjusted AHI did not occur in the same extent. This was expected as the more severe events which tend to remain during the weight loss have greater importance in adjusted AHI, while the event severity is neglected in AHI.

Forehead EEG electrode set versus full-head scalp EEG in 100 patients with altered mental state.

BACKGROUND: Acute EEG is vastly underutilized in acute neurological settings. The most common reason for this is simply the fact that acute EEG is not available when needed or getting EEG is delayed as it requires trained technicians and equipment to be properly recorded. We have recently described a handy disposable forehead EEG electrode set that is suitable for acute emergency EEG recordings. The specific objective in this study was to assess the forehead electrode's utility when the clinical demand was to exclude SE. PATIENTS AND METHODS: One hundred consecutive acute neurological patients (53 women, 47 men, age: 18-90 years) with unexplained altered mental state were studied with acute emergency EEG to rule out SE. Electroencephalographic recordings were obtained simultaneously with forehead EEG electrode and routine 10-20 system full-head scalp electrodes to clarify the clinical usefulness of forehead EEG electrode in this setting. Electroencephalographic recordings were interpreted blindly by three experienced clinical neurophysiologists first only based on forehead EEG and then by full-head EEG. RESULTS: Ninety-six out of the 100 patients did not show EEG evidence of SE. There was 100% agreement with forehead and routine EEG. Four out of the 100 patients showed EEG evidence of SE in routine EEG, with 50% agreement between different electrode types. The forehead EEG missed two cases because the EEG findings supporting SE were restricted to the posterior parts of the brain. MAJOR CONCLUSIONS: With a forehead EEG set, the sensitivity of detecting NCSE was 50%. There were no false positive cases yielding a specificity of 100%. Patients with AMS can benefit from forehead EEG recording in prehospital, hospital, and ICU settings. Since EEG recording can be started within a few minutes with the forehead EEG set, it will significantly reduce the delay in treatment of SE. This article is part of a Special Issue entitled "Status Epilepticus".

A Handy EEG Electrode Set for patients suffering from altered mental state.

Although electroencephalography (EEG) is an important diagnostic tool for investigating patients with unexplained altered mental state (AMS), recording of emergency EEG is not a clinical routine. This is mainly due to the cumbersome electrode solutions. A Handy EEG Electrode Set consists of ten EEG, two EOG, two ground and two commutative reference hydrogel-coated silver wire electrodes attached to a thin polyester carrier film. The clinical usefulness of the Handy EEG Electrode Set was tested in 13 patients (five females, eight males) with AMS. EEG recordings were conducted at the same time with a standard 10-20 electrode set. The registration in the first patient case without the behind-ear electrodes (T9 and T10), indicated that these electrodes are very crucial to provide clinically relevant information from posterior regions of brain. In following 12 cases, the sensitivity and specificity for detecting EEG abnormality based on the Handy EEG Electrode Set recordings were 83 and 100 %, respectively. The Handy EEG Electrode Set proved to be easy to use and to provide valuable information for the neurophysiological evaluation of a patient suffering from AMS. However, further studies with larger number of patients are warranted to clarify the true diagnostic accuracy and applicability of this approach.

Effect of different oxygen desaturation threshold levels on hypopnea scoring and classification of severity of sleep apnea.

PURPOSE: Recently, there has been a debate about the rules used to score hypopnea events. The purpose of this study was to examine the effect of different oxygen desaturation threshold (ODT) levels on the apnea-hypopnea index (AHI) and on a recently introduced parameter, adjusted AHI. Adjusted AHI incorporates the severity of individual breathing cessation events. We also aimed to clarify the impact of the different ODT levels on the current classification of obstructive sleep apnea (OSA) severity. METHODS: Ambulatory polygraphic recordings of 68 patients (19 F/49 M, median age 53.2 years, AHI ≥5) were analyzed retrospectively. Hypopneas were defined as ≥30% drop in airflow for ≥10 s associated with ≥2% oxygen desaturation (ODT2%), and after that, using stricter ODT criteria (ODT3%-ODT8%). RESULTS: Compared to ODT4%, the ODT3% resulted in 5.6 events/h higher median conventional AHI, but only 1.5 events/h higher median adjusted AHI. A significant rearrangement of patients between the clinical severity categories took place when using different ODTs. When assessing with ODT3% instead of ODT4%, the portion of the patients with moderate or severe OSA (AHI ≥15) raised from 29.4 to 73.5% using conventional AHI, but only marginally, i.e., from 73.5 to 77.9%, using the adjusted AHI. CONCLUSIONS: The conventional AHI was found to be susceptible even to minor changes in ODT level which may lead to substantial variability in AHI-based classification of disease severity. Since the adjusted AHI comprises information on severity of individual breathing cessations, it reduces the variability related to ODT levels used in hypopnea scoring and can increase the accuracy of estimation of OSA severity.

Novel screen printed electrode set for routine EEG recordings in patients with altered mental status.

There is a growing need for an easy to use screening tool for the assessment of brain's electrical function in patients with altered mental status (AMS). The purpose of this study is to give a brief overview of the state-of-the-art in electrode technology, and to present a novel sub-hairline electrode set developed in our research group. Screen-printing technology was utilized to construct the electrode set consisting of ten electroencephalography (EEG) electrodes, two electrooculography (EOG) electrodes, two ground electrodes and two reference electrodes. Electrical characteristics of hydrogel-coated silver ink electrodes were found adequate for clinical EEG recordings as assessed by electrical impedance spectroscopy (EIS). The skin-electrode impedances remain stable and low enough at least two days enabling high-quality long-term recordings. Due to the proper material selection, thin ink layers and detachable zero insertion force (ZIF) - connector, electrode was observed to be CT- and MRI-compatible allowing imaging without removing the electrodes. Pilot EEG recordings gave very promising results and an on-going clinical trial with larger number of patients will show the true feasibility of this approach.

New disposable forehead electrode set with excellent signal quality and imaging compatibility.

The use of emergency electroencephalography (EEG) in clinical practice is limited in part due to the lack of commercially available EEG monitoring sets that are suitable for rapid and simple use. The aim of this study was to develop a rapid and simple-to-use disposable forehead EEG electrode set for routine use that is also suitable for long-term monitoring. The EEG set we developed consists of 12 hydrogel-coated electrodes (10 recording electrodes, plus a reference and ground electrode) attached to a solid polymer film. The developed EEG set was compared to the full conventional 10-20 electrode setup in terms of the ability to detect epileptiform abnormalities in two critically ill patients. The technical quality of the EEG signal from the newly developed electrode set was excellent, and status epilepticus was reliably detected with this EEG set. Electric performance testing showed that the impedance spectra of the developed EEG electrodes were comparable to those of three commercially available, disposable electrodes, and the noise level was lower than that of the commercial electrodes. The developed EEG set is also MRI and CT compatible and lacks any signs of imaging artefacts or heat induction. These promising results provide a reason to expect that the developed EEG set may be applicable to situations in which the full, conventional 10-20 electrode setup is not available.

Osteogenesis of human mesenchymal stem cells on micro-patterned surfaces.

Osteogenic responses of human mesenchymal stromal cells (hMSCs) were compared on square-patterned, inverse square-patterned, and planar titanium, chromium, diamond-like carbon (DLC), and tantalum; hypothesis was that both the materials and patterns affect osteogenesis. Samples were produced using photolithography and physical vapor deposition. Early-marker alkaline phosphatase (ALP) and mid-markers, small body size and mothers against decapentaplegic-related protein-1 (SMAD1), runt-related transcription factor-2 (RUNX2), and osteopontin were studied using quantitative real-time polymerase chain reaction. ALP and hydroxyapatite, were colorimetrically studied. ALP reached highest values on both patterned titanium samples, but mid-markers disclosed that it was already lagging behind planar and inverse patterned tantalum. Hydroxyapatite formation disclosed that osteo-induced hMSCs passed all the differentiation stages (except on planar chromium). Presence of hydroxyapatite disclosed that both types of patterning promoted (p < 0.001) osteogenesis compared to planar samples. Results suggest that the osseocompatibility/integration of implants could be improved by changing the monotonous and featureless implant-host interface into micro-patterned interface to provide physical differentiation cues.

Formation and retention of staphylococcal biofilms on DLC and its hybrids compared to metals used as biomaterials.

Staphylococcus epidermidis and Staphylococcus aureus cause most of the implant-related infections. Antibiotic treatment often fails and cure requires surgical intervention. It was hypothesized that biomaterial coatings resistant to biofilms offer a preventive option. Physical vapour deposited diamond-like carbon (DLC) and its polytetrafluoroethylene (DLC-PTFE-h) and polydimethylsiloxane (DLC-PDMS-h) hybrids were compared to titanium (Ti), tantalum (Ta) and chromium (Cr) thin films on silicon wafers for their resistance against formation and/or retention of biofilms produced by S. epidermidis and S. aureus in vitro. Sample surfaces were characterized for surface topography, contact angle and zeta-potential, because such properties might affect the biofilm. Biofilm was stained using calcofluor white and analysed in fluorescence microscopy using morphometry. Sixteen hour incubation was selected in pilot tests; at this checkpoint Ti, Ta, Cr and DLC-PDMS-h were almost fully covered by biofilm, but DLC and DLC-PTFE-h were only partially biofilm coated by S. epidermidis (88±26%, p<0.001 and 56±39%, p<0.001, respectively) or S. aureus (81±24%, p<0.001 and 51±26%, p<0.001, respectively). DLC and its PTFE hybrid offer a potential biofilm hostile surface coating for implants and medical devices. This ability to resist biofilm formation and attachment could not be explained by only one factor, but it seems to be related to a combination of various properties, with electrokinetic streaming potential and protein coating being particularly important for its outcome.

In vitro adhesion of staphylococci to diamond-like carbon polymer hybrids under dynamic flow conditions.

This study compares the ability of selected materials to inhibit adhesion of two bacterial strains commonly implicated in implant-related infections. These two strains are Staphylococcus aureus (S-15981) and Staphylococcus epidermidis (ATCC 35984). In experiments we tested six different materials, three conventional implant metals: titanium, tantalum and chromium, and three diamond-like carbon (DLC) coatings: DLC, DLC-polydimethylsiloxane hybrid (DLC-PDMS-h) and DLC-polytetrafluoroethylene hybrid (DLC-PTFE-h) coatings. DLC coating represents extremely hard material whereas DLC hybrids represent novel nanocomposite coatings. The two DLC polymer hybrid films were chosen for testing due to their hardness, corrosion resistance and extremely good non-stick (hydrophobic and oleophobic) properties. Bacterial adhesion assay tests were performed under dynamic flow conditions by using parallel plate flow chambers (PPFC). The results show that adhesion of S. aureus to DLC-PTFE-h and to tantalum was significantly (P < 0.05) lower than to DLC-PDMS-h (0.671 ± 0.001 × 10(7)/cm(2) and 0.751 ± 0.002 × 10(7)/cm(2) vs. 1.055 ± 0.002 × 10(7)/cm(2), respectively). No significant differences were detected between other tested materials. Hence DLC-PTFE-h coating showed as low susceptibility to S. aureus adhesion as all the tested conventional implant metals. The adherence of S. epidermidis to biomaterials was not significantly (P < 0.05) different between the materials tested. This suggests that DLC-PTFE-h films could be used as a biomaterial coating without increasing the risk of implant-related infections.

Enhancement of silicon using micro-patterned surfaces of thin films.

Micro-textured biomaterials might enhance cytocompatibility of silicon-based micro-electro-mechanical system (bio-MEMS) dummies. Photolithography-physical vapour deposition was used to produce diamond-like carbon (DLC) or Ti squares and circles on silicon, and also their inverse replicas; then DLC and Ti were compared for their guiding potential, using a SaOS-2 cell model. Scanning electron microscopy at 48 hours indicated cells were well-spread on large-sized patterns (several cells on one pattern) and assumed the geometrical architecture of underlying features. Medium-sized patterns (slightly smaller than solitary indicator cells) were inhabited by singular cells, which stretched from one island to another, assuming longitudinal or branching morphologies. On small-sized patterns (much smaller than individual cells;rpar; cells covered large micro-textured areas, but cellular filopodia bypassed the bare silicon. Immunofluorescence and confocal laser scanning microscopy indicated that the actin cytoskeleton and vinculin-containing adhesion junctions were present on the patterned areas, but not on the bare silicon. Cell density/coverage disclosed a 3.4-3.7-fold preference for the biomaterial patterns over silicon substrate (p 0.001). Differences in the cellular response between materials were lost at 120 hours when cells were confluent. The working hypothesis was proven; enhancement by micro-patterning depends on the pattern size, shape and material and can be used to improve biocompatibility during the initial integration phase of the device.

Surface characterization and in vitro biocompatibility assessment of photosensitive polyimide films.

Polyimide (PI) is a commonly used polymer in microelectronics. Recently, numerous PI-based flexible neural interfaces have been developed for reducing mechanical mismatch between rigid implant and soft neural tissue. Most approaches employ non-photosensitive PI, which has been proven earlier to be biocompatible. However, photosensitive polyimide (PSPI) would simplify device fabrication remarkably, but its biocompatibility has been only sparsely reported. In this study, cytotoxicity of spin-coated PSPI (HD Microsystems PI-2771) and conventional PI (HD Microsystems PI-2525) films were evaluated in vitro using BHK-21 fibroblasts according to the ISO-10993-5 standard. PSPIs were tested as cured at a temperature of 200 degrees C (PI-2771-200) and 350 degrees C (PI-2771-350). The PI film surfaces were characterized in terms of their roughness, energy and zeta potential which are hypothesized to affect cell-material interactions. The values of the total surface free energy (SFE), and its polar and dispersive component, were significantly (p<0.001) greater for the PI-2525 film (SFE: 47.3 mJ/m2) than for the PI-2771-200 (25.6 mJ/m2) or PI-2771-350 films (26.2 mJ/m2). The curing temperature of the PI-2771 had a significant effect on the zeta potential values (p<0.001), but not on surface energy (p=0.091) or roughness (p=0.717). The results from the MTS proliferation assays and live/dead staining revealed that PSPI is almost as non-cytotoxic as conventional PI and polyethylene (negative control). The morphology and spreading of BHK-21 cells were similar on all the PI materials tested. In conclusion, PSPI seems to be a promising biocompatible material, while further studies in vitro and in vivo are needed to clarify the long-term effects.

Adhesion, spreading and osteogenic differentiation of mesenchymal stem cells cultured on micropatterned amorphous diamond, titanium, tantalum and chromium coatings on silicon.

It was hypothesized that human mesenchymal stromal cell (hMSC) can be guided by patterned and plain amorphous diamond (AD), titanium (Ti), tantalum (Ta) and chromium (Cr) coatings, produced on silicon wafer using physical vapour deposition and photolithography. At 7.5 h hMSCs density was 3.0-3.5 x higher (P < 0.0003, except Ti) and cells were smaller (68 vs. 102 microm, P 0.000006-0.02) on patterns than on silicon background. HMSC-covered surface of the background silicon was lower on Ti than AD patterns (P = 0.015), but at 5 days this had reversed (P = 0.006). At 7.5 h focal vinculin adhesions and actin cytoskeleton were outgoing from pattern edges so cells assumed geometric square shapes. Patterns allowed induced osteogenesis, but less effectively than plain surfaces, except for AD, which could be used to avoid osseointegration. All these biomaterial patterns exert direct early, intermediate and late guidance on hMSCs and osteogenic differentiation, but indirect interactions exist with cells on silicon background.

Patterned macroarray plates in comparison of bacterial adhesion inhibition of tantalum, titanium, and chromium compared with diamond-like carbon.

Staphylococcus aureus device-related infection is a common complication in implantology. Bacterial adhesion on implant surfaces is the initial step in the infective process. The aim was to develop a method suitable for quantitative bacterial adherence studies and to test a new diamond-like carbon (DLC) coating against commonly used metallic biomaterials with regards to Staphylococcus aureus adhesion. Patterned silicon chips with spots of tantalum, titanium, chromium, and DLC were produced using ultraviolet lithography and physical vapor deposition. These patterned chips were used as such or glued to array plates, pretreated with serum and exposed to S. aureus (S-15981) for 90 min, followed by acridine orange staining and fluorescence microscopy. An adhesion index showed that the ranking order of the biomaterials was titanium, tantalum, chromium, and DLC, with the DLC being clearly most resistant against colonization with S. aureus. Micropatterned surfaces are useful for quantitative comparison of bacterial adherence on different biomaterials. In the presence of serum, DLC is superior in its ability to resist adhesion and colonization by S. aureus compared with the commonly used biomaterial metals tantalum, titanium, and chromium.