Influence of bovine and human serum albumin on the binding kinetics of biomolecular interactions

Bovine serum albumin (BSA) containing buffers are the standard blocking buffer in biosensing, yet human serum is the intended application for most clinical sensors. However, the effect of human serum albumin (HSA) on binding assays remains underexplored. A simple and well-studied assay (human IgG/goat anti-human IgG) was investigated with a surface plasmon resonance (SPR) sensor to address this fundamental question in sensing. Calibrations were performed with buffers containing various concentrations of bovine or human serum albumin, as well as full and diluted bovine or IgG-depleted human serum. It was found that HSA or human serum, but not BSA or bovine serum, significantly affected the SPR shift and binding constants of the assay. Interestingly, large differences were also observed depending on whether the animal or human antibody was immobilized on the SPR chip for detection, highlighting that matrix protein/analyte/receptor interactions play a significant role in the response. We find that the interaction of soluble HSA with human IgG interferes with the recognition region, affecting the binding constant, and thus results obtained in BSA are not necessarily applicable to clinical samples or in vivo conditions. We also clearly demonstrate why a minimum dilution of 1 : 10 is often required in SPR assays to remove most background effects. Taken together, these results show that: (1) BSA does not affect the binding constant between antibodies and thus serves its purpose well when only surface blocking is intended, (2) HSA is an adequate surrogate for human serum in assay optimization, and (3) blocking buffers should be prepared with HSA in the optimization steps of assays to be translated to human blood or serum.

Robustness enhancement of dynamic spectroscopic ellipsometry by compensating temperature dependency of the monolithic polarizing interferometer

This paper describes a robust dynamic spectroscopic ellipsometer that can provide a highly accurate and reliable real-time spectroscopic polarization measurement capability for various in-line nanoscale measurement applications. The robustness of dynamic spectroscopic ellipsometry is enhanced significantly by employing a compensation channel that removes the temperature dependency of the monolithic polarizing interferometric module, and it results in highly accurate dynamic spectral ellipsometric measurements. We present how the monolithic interferometer is affected by external disturbances and show experimentally that the proposed scheme can provide a few hundreds of times long-term stability enhancement compared with a single-channel-based dynamic spectroscopic ellipsometer scheme.

Cross-validation of ELISA and a portable surface plasmon resonance instrument for IgG antibody serology with SARS-CoV-2 positive individuals

We report on the development of surface plasmon resonance (SPR) sensors and matching ELISAs for the detection of nucleocapsid and spike antibodies specific against the novel coronavirus 2019 (SARS-CoV-2) in human serum, plasma and dried blood spots (DBS). When exposed to SARS-CoV-2 or a vaccine against SARS-CoV-2, the immune system responds by expressing antibodies at levels that can be detected and monitored to identify the fraction of the population potentially immunized against SARS-CoV-2 and support efforts to deploy a vaccine strategically. A SPR sensor coated with a peptide monolayer and functionalized with various sources of SARS-CoV-2 recombinant proteins expressed in different cell lines detected human anti-SARS-CoV-2 IgG antibodies in clinical samples. Nucleocapsid expressed in different cell lines did not significantly change the sensitivity of the assays, whereas the use of a CHO cell line to express spike ectodomain led to excellent performance. This bioassay was performed on a portable SPR instrument capable of measuring 4 biological samples within 30 minutes of sample/sensor contact and the chip could be regenerated at least 9 times. Multi-site validation was then performed with in-house and commercial ELISA, which revealed excellent cross-correlations with Pearson's coefficients exceeding 0.85 in all cases, for measurements in DBS and plasma. This strategy paves the way to point-of-care and rapid testing for antibodies in the context of viral infection and vaccine efficacy monitoring.

Enhancement of Gold Nanoparticle Coupling with a 2D Plasmonic Crystal at High Incidence Angles

2D nanoplasmonic substrates excited in transmission spectroscopy are ideal for several biosensing, metamaterial, and optical applications. We show that their excellent properties can be further improved with plasmonic coupling of Au nanoparticles (AuNPs) on gold-coated nanodisk arrays excited at large incidence angles of up to 50°. The Bragg modes (BM) thereby strongly couple to AuNP immobilized on the plasmonic substrate due to shorter decay length of the plasmon at higher incidence angles, leading to a further enhanced field between the AuNP and the plasmonic substrate. The field was highest and two hotspots were created at orthogonal positions for AuNP located close to the corner of the Au film and Au nanodisk, which was also observed for AuNP dimers. Hybridization between single-stranded DNA (ssDNA) immobilized on the surface of the AuNPs and the capture ssDNA on the gold-coated nanodisk arrays led to at least a 5-fold signal improvement and a 7-fold lower limit of detection at 7 pM for ssDNA-functionalized AuNPs at large incident angles. Thus, we demonstrate that higher field strength can be accessed and the significant advantages of working with high incidence angles with AuNP on a 2D plasmonic crystal in plasmonic sensing.

The research gap in chronic paediatric pain: A systematic review of randomised controlled trials

BACKGROUND AND OBJECTIVE

Chronic pain is associated with significant functional and social impairment. The objective of this review was to assess the characteristics and quality of randomized controlled trials (RCTs) evaluating pain management interventions in children and adolescents with chronic pain.

METHODS

We performed a systematic search of PubMed, Embase and the Cochrane Library up to July 2017. We included RCTs that involved children and adolescents (3 months-18 years) and evaluated the use of pharmacological or non-pharmacological intervention(s) in the context of pain persisting or re-occurring for more than 3 months. Methodological quality was evaluated using the Cochrane Risk of Bias (ROB) Tool.

RESULTS

A total of 58 RCTs were identified and numbers steadily increased over time. The majority were conducted in single hospital institutions, with no information on study funding. Median sample size was 47.5 participants (Q1,Q3: 32, 70). Forty-five percent of RCTs included both adults and children and the median of the mean ages at inclusion was 12.9 years (Q1,Q3: 11, 15). Testing of non-pharmacological interventions was predominant and only 5 RCTs evaluated analgesics or co-analgesics. Abdominal pain, headache/migraine and musculoskeletal pain were the most common types of chronic pain among participants. Methodological quality was poor with 90% of RCTs presenting a high or unclear ROB.

CONCLUSIONS

Evaluation of analgesics targeting chronic pain relief in children and adolescents through RCTs is marginal. Infants and children with long-lasting painful conditions are insufficiently represented in RCTs. We discuss possible research constraints and challenges as well as methodologies to circumvent them.

SIGNIFICANCE

There is a substantial research gap regarding analgesic interventions for children and adolescents with chronic pain. Most clinical trials in the field focus on the evaluation of non-pharmacological interventions and are of low methodological quality. There is also a specific lack of trials involving infants and children and adolescents with long-lasting diseases.

High Figure of Merit (FOM) of Bragg Modes in Au-Coated Nanodisk Arrays for Plasmonic Sensing

Gold-coated nanodisk arrays of nearly micron periodicity are reported that have high figure of merit (FOM) and sensitivity necessary for plasmonic refractometric sensing, with the added benefit of suitability for surface-enhanced Raman scattering (SERS), large-scale microfabrication using standard photolithographic techniques and a simple instrumental setup. Gold nanodisk arrays are covered with a gold layer to excite the Bragg modes (BM), which are the propagative surface plasmons localized by the diffraction from the disk array. This generates surface-guided modes, localized as standing waves, leading to highly confined fields confirmed by a mapping of the SERS intensity and numerical simulations with 3D finite element method. The optimal gold-coated nanodisk arrays are applied for refractometric sensing in transmission spectroscopy with better performance than nanohole arrays and they are integrated to a 96-well plate reader for detection of IgY proteins in the nanometer range in PBS. The potential for sensing in biofluids is assessed with IgG detection in 1:1 diluted urine. The structure exhibits a high FOM of up to 46, exceeding the FOM of structures supporting surface plasmon polaritons and comparable to more complex nanostructures, demonstrating that subwavelength features are not necessary for high-performance plasmonic sensing.

[Anesthesia-resuscitation for intracranial expansive processes in children]

The most frequent space-occupying cerebral lesions in children are brain tumors, mostly posterior fossa tumors and haematoma resulting from arteriovenous malformation rupture. They result in intracranial hypertension, directly or by compression of the cerebrospinal fluid pathway resulting in hydrocephalus. Their localization and compressive effects are responsible for specific neurological deficits and general problems. Posterior fossa lesions carry a high risk of obstructive hydrocephalus, cranial nerves palsy and brain stem compression, pituitary and chiasmatic tumors a risk of blindness, pituitary deficiency and diabetes insipidus, and cortical tumors a risk of motor deficit and epilepsy. All these parameters must be analyzed before choosing anaesthetic protocols, and surgical techniques. In the presence of life-threatening intracranial hypertension, emergency anaesthetic induction, tracheal intubation and ventilation are life-saving. The specific treatment consists in either hydrocephalus derivation, initial medical treatment with osmotherapy, or rarely surgical removal. In other situations, surgical process requires a highly deep, stable anaesthesia with perfect control of cerebral haemodynamics. Surgical positioning is complex for these long lasting procedures and carries specific risks. The most common is venous air embolism in the sitting position that must be prevented by the use of specific measures. In the postoperative period, the risk of neurological and general complications commands close surveillance, fast track extubation must be adapted on an individual basis.

Validity of applying TRISS analysis to paediatric blunt trauma patients managed in a French paediatric level I trauma centre

OBJECTIVE

Using a weighted combination of the Revised Trauma Score (RTS), the Injury Severity Score (ISS), the type of injury (blunt or penetrating) and patient age, the TRISS method is used to calculate the probability of survival (ps) in trauma patients. The goal of this study was to compare the ability of the American Major Trauma Outcome Study (MTOS) norm for adult blunt trauma patients (ADULT) and the specific norm for paediatric patients (PED) to estimate the ps of injured children using TRISS methodology.

DESIGN

Retrospective analysis using a paediatric trauma patient database.

SETTING

A French level 1 paediatric trauma centre.

PATIENTS

Four hundred seven consecutive paediatric blunt trauma patients, treated over a 3-year period.

MEASUREMENTS

The observed and expected survivals were compared, using the M, W and Z scores, with both ADULT and PED. The W score is the number of survivors more or less than expected from the MTOS predictions for 100 patients. A Z score, which measures the significance of W, between -1.96 and +1.96, indicates no significant difference between observed and expected survivors. A value of M less than 0.88 indicates a disparity in the severity match between the study group and the MTOS group. We calculated the standardised W score (Ws), which represents the W score that would have been observed if the case mix of severity was identical to that of the MTOS group. Accordingly, a standardised Z score (Zs) was also calculated. In addition, we calculated the area under the receiver operating curve (aROC) using both norms, while calibration was also assessed by calculation of the Hosmer-Lemeshow goodness-of-fit tests.

RESULTS

Using PED, the number of actual survivors (n = 364) was not significantly different from the MTOS (n = 358). The value of M, 0.65, indicated a disparity in the severity match between the study group and the MTOS group, due to a higher proportion of patients with lower ps (TRISS < 0.95, 52 vs 27%). We was +1.06% (95% confidence interval -0.34 to 2.08) and Zs was 1.48, indicating no significant difference from the MTOS. Using ADULT, the number of observed survivors (n = 364) was significantly higher than that expected (n = 354), with a W score of +2.70% (Z = +1.98, p < 0.05). There was a disparity in the severity match (M = 0.67) between the study group and the MTOS group, due to a higher proportion of patients with lower ps. Ws was +1.32% (95% confidence interval -0.12 to 2.37) and Zs = +1.79 (NS), indicating no significant difference from the MTOS. The Hosmer-Lemeshow statistics indicated that ADULT (Cg = 7.24, p = 0.51; Hg = 4.45, p = 0.81) and PED (Cg = 6.08, p = 0.64; Hg = 3.55, p = 0.90) provided sufficient goodness-of-fit. There was no significant difference in the aROC of the TRISS between the two norms (0.935 +/- 0.050 vs 0.936 +/- 0.050; NS).

CONCLUSION

Both adult and paediatric norms were equally good predictors of the probability of survival of injured children, provided that Ws and Zs are used when there is a disparity in the severity match between the study group and the MTOS group.

Emergency management of deeply comatose children with acute rupture of cerebral arteriovenous malformations

PURPOSE

To assess the impact of emergency management on mortality and morbidity of acute rupture of cerebral arteriovenous malformations resulting in deep coma in children, and the factors predicting outcome.

METHODS

Retrospective chart review of 20 children with a Glasgow Coma Scale < or = 8 with acute hemorrhagic stroke from a cerebral arteriovenous malformation rupture was conducted. Protocol included: early resuscitation with tracheal intubation and ventilation after induction of anesthesia with sufentanil, and benzodiazepine, and mannitol 20% or hypertonic saline 7.5% infusion for life-threatening brain herniation. Radiological exploration was limited to contrast-enhanced CT scan preceding immediate surgical decompression. Postoperatively, children were deeply sedated and intracranial pressure monitoring allowed titration with osmotherapy, vasopressors, hyperventilation or barbiturate coma to control cerebral perfusion pressure. Analysis used stratification of the type of hemorrhage (supra or infra tentorial), location (intraparenchymal and subarachnoid, intraparenchymal and intraventricular or intraventricular alone) and relationship between presentation, evolution with resuscitation, type of cerebral lesion, and outcome.

RESULTS

Patients had a severe initial presentation (median Glasgow Coma Scale five), eight had unilateral and eight bilateral third nerve palsy. Compressive hematoma in supratentorial localisation represented 75% of the cases. Global mortality was 40%. Persistence of mydriasis after resuscitation increased mortality to 75%. Massive intraventricular flooding was associated with increased mortality. Good functional outcome was achieved in survivors.

CONCLUSION

Acute rupture of an AVM can result in rapidly progressing coma. Emergency management with early resuscitation, minimal radiological exploration before rapid surgical decompression results in a mortality rate of 40%, but a good functional outcome can be expected in the survivors.

Complications of emergency tracheal intubation in severely head-injured children

A high incidence of unsuccessful attempts and complications has been reported when emergency tracheal intubation (ETI) is performed outside the hospital in severely injured children. The aim of this prospective series was to analyse the incidence and related risk factors of complications of emergency tracheal intubation. The time to complete successful ETI and occurrence of incidents, e.g. cough reflex, hypoxia or spasm were related to the experience of the physician performing intubation and the use of drugs to facilitate ETI. The incidence of hypoxia, hypercarbia, postintubation complications such as extubation stridor and long-term sequelae were noted. Of the 188 children, 78% were successfully intubated at the site of the accident, 10% upon arrival at a local hospital from where they were secondarily transferred and 12% upon admission to our trauma centre. The most severely injured children were intubated in the field in 98% of cases without failure, nor life-threatening complications related to ETI. The experience of the operator influenced the number of attempts and the time to complete successful intubation. Immediate incidents were noted in 25% of children, e.g. cough in 18%. The regimen of drugs, but not level of consciousness, influenced the incidence of immediate incidents; without drugs, more than 67% experienced incidents. Early tracheal intubation and controlled ventilation resulted in adequate ventilation upon arrival (mean PaO2 of 35.8+/-24 kPa, mean PaCO2 of 4.35+/-1 kPa). Long-term complications, including transient stridor upon extubation in 33% of the cases, and laryngeal granuloma or tracheal stenosis, were comparable to those in other series. ETI in shocked patients and pulmonary infection in hospital, but not the technique of ETI, increased the risks of long-term complications. Emergency tracheal intubation can be performed safely in the field, and results in adequate ventilation during transportation of severely injured children, provided that it can be performed by trained physicians using adequate drugs to facilitate intubation.

Non-invasive aortic blood flow measurement in infants during repair of craniosynostosis

We have assessed the potential clinical benefit of a new echo-Doppler device (Dynemo 3000) which provides a continuous measure of aortic blood flow (ABF) using an aortic flowmeter and a paediatric oesophageal probe, during repair of craniosynostosis in infants under general anaesthesia. The data recorded included: ABFi (i = indexed to body surface area), stroke volume (SVi), systemic vascular resistance (TSVRi), pre-ejection period (PEP), left ventricular ejection time (LVET), mean arterial pressure (MAP), heart rate (HR) and central venous pressure (CVP). Data were collected: before (T1) and 3 min after skin incision (T2), at the time of maximal haemorrhage (T3) and at the end of the procedure (T4). Twelve infants (aged 7.0 (range 6-12) months) were included. ABFi, MAP and CVP were significantly lower at T3 compared with T1 (2.0 (0.8) vs 3.0 (0.8) litre min-1 m-2, 46.1 (5.8) vs 65.2 (8.9) mm Hg and 2.8 (1.6) vs 5.2 (2.1) mm Hg; P < 0.05). PEP/LVET ratio was significantly lower at T2 compared with T1 (0.25 (0.05) vs 0.30 (0.06)) and increased at T4 (0.36 (0.04); P < 0.05). These preliminary results suggest that this non-invasive ABF echo-Doppler device may be useful for continuous haemodynamic monitoring during a surgical procedure associated with haemorrhage in infants.

Predictive factors of outcome in severely traumatized children

To identify risk factors associated with death in traumatized children, we prospectively studied 507 consecutive patients (7+/-4 yr) admitted to a level I pediatric trauma center over a 3-yr period. Pediatric Trauma Score (PTS), Glasgow Coma Scale (GCS) score, and Injury Severity Score (ISS) were calculated. Age, injury mechanism, injury pattern, and initial critical care were recorded. Univariate and multivariate analyses were performed for potential risk factors associated with mortality. Receiver operating characteristic curves were used to determine threshold values of variables identified by univariate analysis. Most children suffered from blunt trauma (99.6%), and head trauma was noted in 85%. Median values (range) of GCS scores, PTS, and ISS were 10 (3-15), 7 (-4 to 12), and 16 (3-75), respectively. The mortality rate was 12%. Using multivariate analysis, death was significantly associated with an ISS > or = 25 (odds ratio [OR] 22.2, 95% confidence interval 2.8-174.9), GCS score < or = 7 (OR 4.77, 1.8-12.7), emergency blood transfusion > or = 20 mL/kg (OR 4.3, 2.1-9.1), and PTS < or = 4 (OR 3.7, 1.4-9.7). An ISS > or = 25, GCS score < or = 7, immediate blood transfusion > or = 20 mL/kg, and PTS < or = 4 were significant and independent risk factors of death in an homogenous population of severely injured children. The probability of traumatic death was therefore 0 (95% confidence interval 0-0.0135) in children with no one of these threshold values in the four predictive factors and 0.63 (95% confidence interval 0.47-0.76) in those children with all the threshold values.

IMPLICATIONS

Methods used for evaluating outcome of trauma patients have essentially been derived from adult series, and attempts to apply them to children have usually been inaccurate. Univariate and multivariate analyses were performed to identify risk factors associated with death in severely traumatized children, and Receiver operating characteristic curves were used to determine threshold values.

Prevention of venous air embolism in paediatric neurosurgical procedures performed in the sitting position by combined use of MAST suit and PEEP

We studied 60 children undergoing neurosurgical procedures in the sitting position. Routine monitoring included ECG, pulse oximetry, invasive arterial pressure, in particular mean arterial pressure (MAP), and right atrial pressure (RAP). Children were allocated to two groups. In group B lower body positive pressure and positive end-expiratory pressure (PEEP) were used for preventing venous air embolism (VAE). In this group, antishock trousers (MAST suit) were adjusted in supine children. After induction of anaesthesia, different positions were studied: supine and sitting before MAST suit inflation, sitting with MAST suit inflated up to a pressure of 40 mmHg in the lower compartments and 30 mmHg in the abdominal compartment, and finally a combination of lower body positive pressure and PEEP of 8-10 cm H2O. In group A no MAST suit or PEEP was used. Continuous monitoring of end-tidal carbon dioxide pressure throughout (PE'CO2) was used to detect VAE. In order to evaluate the transmission of pressures from the right atrium to the veins at the base of the skull, jugular bulb venous pressure (JBVP) was measured in 20 patients by retrograde catheterization. The incidence of VAE was compared in the two groups. On placing children into the sitting position, a significant decrease in RAP and JBVP was noted without significant changes in MAP in the two groups. Inflation of the MAST suit induced a dramatic increase in RAP and JBVP, reinforced by addition of PEEP. There was a strong positive relationship between RAP and JBVP. There were no deleterious side effects or differences between the two groups in peroperative blood product requirements or surgical general conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood loss during repair of craniosynostosis

Surgical repair of craniosynostosis carries a high risk with large blood losses. Over a 2-yr period, we have managed 115 patients undergoing craniosynostosis repair with peroperative haemodilution to achieve a final PCV of 0.28-0.35. Measurements of PCV allowed calculation of estimated blood losses and transfused volumes in terms of red blood cell mass. Total estimated red cell volume lost was 91 +/- 66% of patient's estimated red blood cell volume during the peroperative period. The type of skull deformation and surgical procedure determined the extent of peroperative bleeding. Peroperative transfusion was satisfactory in 48% of patients and slight overtransfusion was noted in 32%. During the postoperative period, liberal administration of blood led to overtransfusion and possibly unnecessary transfusion in 74% of patients. Because of the well known risks of transmission of infectious disease, strict volume compensation with development of haemodilution and autotransfusion procedures should be used to limit these risks.

[Surgery in complex forms of transposition of the great vessels: long-term results in a series of 100 cases]

A series of 100 patients with complex forms of transposition of the great arteries (TGA) were operated upon over a 10 year period. Group 1 consisted of 13 TGA with pulmonary stenosis (PS), usually treated by an atrial baffle and direct repair of the stenosis. There was no operative or late mortality in this group and the long-term results were generally good (10/13). Group II comprised 29 TGA with ventricular septal defect (VSD) and PS. Seven Rastelli procedures gave 4 good results. Twenty two operations, associating atrial baffle, repair of VSD and PS (17 direct procedures, 5 left ventricle-pulmonary artery tube) were associated with a high mortality (5 operative and 4 late deaths) and 10 good long-term results. Group III comprised 58 TGA with VSD. Up to 1977 (n = 33) treatment consisted of atrial baffle + repair of VSD +/- removal of previous banding. Mortality was high (11 operative and 8 late deaths) with only 8 good long-term results. Since 1977, these patients have been treated by complete anatomical repair, the operative mortality of which is higher in the period under study (9/23) but the long-term results are much better. The surgical indications in our Department are based on the analysis of these results. In Group I only very significant PS is treated, either by left ventricle-pulmonary artery tube or direct repair depending on the form of the stenosis. In Group II, where the results based on atrial baffle are poor, a Rastelli procedure is preferred and especially its variants which avoid the use of prosthetic materials on the pulmonary trunk. In Group III, anatomical correction at the level of the great arteries is the routine procedure, the only point of discussion being the possibility of prior banding.