Does Prior Surgery for Femoroacetabular Impingement Compromise Hip Arthroplasty Outcomes?

BACKGROUND

Open and arthroscopic approaches have been described to address femoroacetabular impingement (FAI). Despite good outcomes, there is a subset of patients who subsequently require total hip arthroplasty (THA). However, there is a paucity of data on the outcomes of THA after surgery for FAI. The purpose of this study was to determine whether clinical outcomes of THA are affected by prior open or arthroscopic treatment of FAI.

METHODS

This case-matched retrospective review included 23 patients (24 hips) that underwent THA after previous surgery for FAI (14 arthroscopic and 10 open) and compared them to 24 matched controls with no history of prior surgery on the operative hip. The controls were matched for age, sex, surgical approach, implants used, and preoperative modified Harris hip score (mHHS) did not differ between groups. The primary outcome measure was the mHHS. Operative time, blood loss, and the presence of heterotopic ossification after THA were also compared between groups.

RESULTS

There was no significant difference in mean mHHS between the FAI treatment group 92.9 ± 12.7 and controls 95.2 ± 6.6 (P = .43) at a mean follow-up after THA of 33 (24-70) months. Increased operative times were noted for THA after surgical hip dislocation (SHD; mean 109.3 ± 29.8) compared to controls (mean 88.0 ± 24.2; P < .05). There was no significant difference in blood loss between groups. The occurrence of heterotopic ossification was significantly higher after SHD compared to controls (P < .05).

CONCLUSIONS

Clinical outcomes after THA are not affected by prior open or arthroscopic procedures for FAI. However, increased operative times and an increased risk of heterotopic ossification were noted after SHD.

Removing a well-fixed femoral sleeve during revision total knee arthroplasty

The following surgical technique describes a case of a 51-year-old man with severe juvenile rheumatoid arthritis that required a 2-stage revision of an infected revision total knee implant. The patient had previously been implanted with a revision rotating platform, constrained condylar device which gained excellent fixation through the use of diaphyseal-engaging stems, and a well-ingrown, fully porous-coated femoral metaphyseal sleeve. To avoid intraoperative complications while removing the femoral sleeve, a novel technique for femoral sleeve extraction was used. Using this technique, the femoral sleeve was successfully removed without intraoperative fracture or substantial bone loss.

Preoperative Radiographic Evaluation of Patients With Pelvic Discontinuity

BACKGROUND

Pelvic discontinuity (PD) is a rare but devastating mechanism of failure in total hip arthroplasty. Radiographic findings have been described for the identification of PD. However, no study has specifically examined radiographic parameters and the utility of specific views in the preoperative identification of PD.

METHODS

We performed a retrospective review of 133 patients who underwent acetabular revision for PD. Preoperative radiographic studies were reviewed including anteroposterior pelvis (AP; n = 133), true lateral hip (n = 132), Judet (n = 47), false profile (n = 4), and computed tomography scans (n = 14). Radiographs were read by the senior authors to identify the following parameters suggestive of PD: visible fracture line, medial migration of the inferior hemipelvis, and obturator ring asymmetry.

RESULTS

Using only the AP view, the fracture line was visible in 116 (87%), medial migration of the inferior hemipelvis in 126 (95%), and obturator ring asymmetry in 114 (86%). A fracture line was visualized in 65 of 132 hips (49%) evaluated with laterals, 36 of 47 hips (77%) evaluated with Judet views, 3 of 4 (75%) evaluated with a false profile view, and 10 of 14 (71%) evaluated with computed tomography.

CONCLUSION

Preoperative evaluation with a combination of an AP pelvis radiograph, plus a true lateral radiograph of the hip, plus Judet films in combination with the criteria for discontinuity defined in this article, allowed for identification of PD in a 100% of patients.

Noninvasive Hemoglobin Monitoring: A Rapid, Reliable, and Cost-Effective Method Following Total Joint Replacement

BACKGROUND

Noninvasive hemoglobin (nHgb) monitoring was initially introduced in the intensive care setting as a means of rapidly assessing Hgb values without performing a blood draw. We conducted a prospective analysis to compare reliability, cost, and patient preference between nHgb monitoring and invasive Hgb (iHgb) monitoring performed via a traditional blood draw.

METHODS

We enrolled 100 consecutive patients undergoing primary or revision total hip or total knee arthroplasty. On postoperative day 1, nHgb and iHgb values were obtained within thirty minutes of one another. iHgb and nHgb values, cost, patient satisfaction, and the duration of time required to obtain each reading were recorded. The concordance correlation coefficient (CCC) was utilized to evaluate the agreement of the two Hgb measurement methods. Paired t tests and Wilcoxon signed-rank tests were utilized to compare mean Hgb values, time, and pain for all readings.

RESULTS

The mean Hgb values did not differ significantly between the two measurement methods: the mean iHgb value (and standard deviation) was 11.3 ± 1.4 g/dL (range, 8.2 to 14.3 g/dL), and the mean nHgb value was 11.5 ± 1.8 g/dL (range, 7.0 to 16.0 g/dL) (p = 0.11). The CCC between the two Hgb methods was 0.69. One hundred percent of the patients with an nHgb value of ≥ 10.5 g/dL had an iHgb value of >8.0 g/dL. The mean time to obtain an Hgb value was 0.9 minute for the nHgb method and 51.1 minutes for the iHgb method (p < 0.001). At our institution, the cost of iHgb monitoring is approximately $28 per blood draw compared with $2 for each nHgb measurement, resulting in a savings of $26 per Hgb assessment when the noninvasive method is used.

CONCLUSIONS

Noninvasive Hgb monitoring was found to be more efficient, less expensive, and preferred by patients compared with iHgb monitoring. Providers could consider screening total joint arthroplasty patients with nHgb monitoring and only order iHgb measurement if the nHgb value is <10.5 g/dL. If this protocol had been applied to the first blood draw in our 100 patients, approximately $2000 would have been saved. Extrapolated to the U.S. total joint arthroplasty practice, approximately $20 million could be saved annually.

Primary total knee arthroplasty in a patient with a chronic extensor mechanism deficiency

A 44-year-old female presented with a chief complaint of left knee pain and dysfunction. The patient had a complex surgical history including patellar fracture repair, subsequent patellar ligament repair, and ultimately allograft reconstruction which was complicated by septic arthritis requiring graft resection. On presentation to our clinic, she was noted to have significant degenerative disease in addition to chronic extensor mechanism deficiency. She underwent primary total knee arthroplasty with concomitant tibial tubercle osteotomy and advancement. The patient has had an excellent result postoperatively including return of full range of motion without residual extensor lag.

Duffy blood group phenotype-genotype correlations using high-resolution melting analysis PCR and microarray reveal complex cases including a new null FY*A allele: the role for sequencing in genotyping algorithms

BACKGROUND AND OBJECTIVES

Duffy blood group phenotypes can be predicted by genotyping for single nucleotide polymorphisms (SNPs) responsible for the Fy(a) /Fy(b) polymorphism, for weak Fy(b) antigen, and for the red cell null Fy(a-b-) phenotype. This study correlates Duffy phenotype predictions with serotyping to assess the most reliable procedure for typing.

MATERIALS AND METHODS

Samples, n = 155 (135 donors and 20 patients), were genotyped by high-resolution melt PCR and by microarray. Samples were in three serology groups: 1) Duffy patterns expected n = 79, 2) weak and equivocal Fy(b) patterns n = 29 and 3) Fy(a-b-) n = 47 (one with anti-Fy3 antibody).

RESULTS

Discrepancies were observed for five samples. For two, SNP genotyping predicted weak Fy(b) expression discrepant with Fy(b-) (Group 1 and 3). For three, SNP genotyping predicted Fy(a) , discrepant with Fy(a-b-) (Group 3). DNA sequencing identified silencing mutations in these FY*A alleles. One was a novel FY*A 719delG. One, the sample with the anti-Fy3, was homozygous for a 14-bp deletion (FY*01N.02); a true null.

CONCLUSION

Both the high-resolution melting analysis and SNP microarray assays were concordant and showed genotyping, as well as phenotyping, is essential to ensure 100% accuracy for Duffy blood group assignments. Sequencing is important to resolve phenotype/genotype conflicts which here identified alleles, one novel, that carry silencing mutations. The risk of alloimmunisation may be dependent on this zygosity status.

How do I get out of this jam? Overcoming common intraoperative problems in primary total hip arthroplasty

Prompt attention is typically required in managing intraoperative problems associated with total hip arthroplasty. There is often limited time for consultation or a review of the literature. The treating surgeon should be familiar with treatment options, favored treatment methods, and should be able to implement the most appropriate and optimal treatment for his or her patient. Common intraoperative complications associated with primary total hip arthroplasty include difficulty gaining sufficient exposure, problems with cup fixation, challenges with implant anteversion, intraoperative fracture of the femur, and difficulties with intraoperative limb length and hip instability.

A novel FY*A allele with the 265T and 298A SNPs formerly associated exclusively with the FY*B allele and weak Fy(b) antigen expression: implication for genotyping interpretative algorithms

BACKGROUND AND OBJECTIVES

An Australian Caucasian blood donor consistently presented a serology profile for the Duffy blood group as Fy(a+b+) with Fy(a) antigen expression weaker than other examples of Fy(a+b+) red cells. Molecular typing studies were performed to investigate the reason for the observed serology profile.

MATERIAL AND METHODS

Blood group genotyping was performed using a commercial SNP microarray platform. Sanger sequencing was performed using primer sets to amplify across exons 1 and 2 of the FY gene and using allele-specific primers.

RESULTS

The propositus was genotyped as FY*A/B, FY*X heterozygote that predicted the Fy(a+b+(w) ) phenotype. Sequencing identified the 265T and 298A variants on the FY*A allele. This link between FY*A allele and 265T was confirmed by allele-specific PCR.

CONCLUSION

The reduced Fy(a) antigen reactivity is attributed to a FY*A allele-carrying 265T and 298A variants previously defined in combination only with the FY*B allele and associated with weak Fy(b) antigen expression. This novel allele should be considered in genotyping interpretative algorithms for generating a predicted phenotype.

Effect of epinephrine on survival after cardiac arrest: a systematic review and meta-analysis

The use of epinephrine is currently recommended as a treatment option for patients with cardiac arrest. The primary objective of this systematic review was to determine if epinephrine use during cardiac arrest is associated with improved survival to hospital discharge. MEDLINE, EMBASE, The Cochrane Library (Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science, International Pharmaceutical Abstracts, and Biological Abstracts (BIOSIS Previews), and bibliographies of previous systematic reviews. Studies involving patients with cardiac arrest that compared epinephrine to no epinephrine (or placebo) with regard to survival to hospital discharge or 30-day survival. Randomized controlled trials (RCTs) and observational studies were included. The results were stratified into three groups: 1) RCTs, 2) observational studies with unadjusted data (observational-U), and 3) observational studies with adjusted data using multivariate analysis (observational-A). There were a total of 10 studies included in the systematic review and nine studies were included in the meta-analysis. The association between epinephrine use and survival to hospital discharge, grouped by study type was not significant for RCTs (OR 2.33, 95% CI 0.85 to 6.40; p=0.10; I2=0.00%) or observational-U studies (OR 1.17, 95% CI 0.67 to 2.07; p=0.58; I2=76.68%). But epinephrine was associated with decreased survival in observational-A studies (OR 0.43, 95% CI 0.40 to 0.48; P<0.01; I2=0.00%). Epinephrine use during cardiac arrest is not associated with improved survival to hospital discharge. Observational studies with a lower-risk for bias suggest that it may be associated with decreased survival.

Unique failure mechanism of a femoral component after revision total hip arthroplasty

As the prevalence of revision total hip arthroplasty increases, the mechanisms of failure of these revisions have become better delineated. Several studies have indicated infection, instability, and aseptic loosening to be the more common mechanisms of failure in revision surgery. However, with increasing numbers of revisions performed, unique mechanisms of failure are being seen, likely related to the implants that are used in the revision setting. Revision implants offer certain advantages over primary implants with the use of modular components. The revision implants allow the surgeon to increase offset and leg length with modular femoral bodies and necks. However, these modular junctions represent additional areas for implant failure. These new methods of failure associated with modular implants are slowly presenting as the use of these implants continues to increase. The authors recently encountered a mechanism of failure that, to their knowledge, has not been described in the literature. They report a 57-year-old man with dissociation of the proximal body from the diaphyseal component of a Wright Medical Link (Memphis, Tennessee) stem prosthesis. The patient presented with an audible click on physical examination, and radiographs confirmed dissociation of the proximal body. The intraoperative findings, treatment method, and proposed mechanisms for this type of failure are presented, as well as insight into potential ways to avoid this type of failure.

Evaluating the prognostic significance of preoperative thrombocytosis in epithelial ovarian cancer

OBJECTIVE

Preoperative thrombocytosis has been implicated as a negative prognostic marker for epithelial ovarian cancer (EOC). We assessed whether thrombocytosis is an independent risk factor for EOC recurrence and death.

METHODS

Perioperative patient characteristics and process-of-care variables (National Surgical Quality Improvement Program (NSQIP)-defined) were retrospectively abstracted from 587 women who underwent EOC staging between 1/2/03-12/29/08. Thrombocytosis was defined as platelet count > 450 × 10(9)/L. Disease-free survival (DFS) and overall survival (OS) were determined using Kaplan-Meier methods. Associations were evaluated with Cox proportional hazards regression and hazard ratios (HR).

RESULTS

The incidence of preoperative thrombocytosis was 22.3%. DFS was 70.8% and 36.0% at 1 and 3 years. OS was 83.3% and 54.3% at 1 and 3 years. Ascites, lower hemoglobin, advanced disease, and receipt of perioperative packed red blood cell transfusion were independently associated with thrombocytosis. Older age and the presence of coronary artery disease were associated with lower likelihood of thrombocytosis. Overall, thrombocytosis was an independent predictor of increased risk of recurrence. Among early stage (I/II) cases, there was a 5-fold increase in the risk of death and nearly 8-fold risk of disease recurrence independently associated with thrombocytosis.

CONCLUSION

Preoperative thrombocytosis portends worse DFS in EOC. In early stage disease, thrombocytosis is a potent predictor of worse DFS and OS and further assessment of the impact of circulating platelet-derived factors on EOC survival is warranted. Thrombocytosis is also associated with extensive initial disease burden, measurable residual disease, and postoperative sequelae. Preoperative platelet levels may have value in primary cytoreduction counseling.

Maternal ghrelin deficiency compromises reproduction in female progeny through altered uterine developmental programming

Ghrelin has a well-known role in the regulation of appetite, satiety, energy metabolism, and reproduction; however ghrelin has not been implicated in reproductive tract development. We examined the effect of ghrelin deficiency on the developmental programming of female fertility. We observed that female wild-type mice born of ghrelin heterozygote dams (i.e. exposed in utero to ghrelin deficiency) had diminished fertility and produced smaller litters. We demonstrate that exposure to in utero ghrelin deficiency led to altered developmental programming of the reproductive tract. The number of ovarian follicles, corpora lutea, and embryos produced were identical in both exposed and unexposed mice. However wild-type embryos transferred to uteri of mice exposed to in utero ghrelin deficiency had a 60% reduction in the rate of embryo implantation compared with those transferred to wild-type unexposed uteri. We identified significant alterations in the uterine expression of four genes critical for implantation and a defect in uterine endometrial proliferation. Taken together, these results demonstrate that the mechanism of subfertility was abnormal endometrial function. In utero exposure to decreased levels of ghrelin led to defects in developmental programming of the uterus and subsequent subfertility in wild-type offspring.

Stabilization of the total force in multi-finger pressing tasks studied with the 'inverse piano' technique

When one finger changes its force, other fingers of the hand can show unintended force changes in the same direction (enslaving) and in the opposite direction (error compensation). We tested a hypothesis that externally imposed changes in finger force predominantly lead to error compensation effects in other fingers thus stabilizing the total force. A novel device, the "inverse piano", was used to impose controlled displacements to one of the fingers over different magnitudes and at different rates. Subjects (n=10) pressed with four fingers at a constant force level and then one of the fingers was unexpectedly raised. The subjects were instructed not to interfere with possible changes in the finger forces. Raising a finger caused an increase in its force and a drop in the force of the other three fingers. Overall, total force showed a small increase. Larger force drops were seen in neighbors of the raised finger (proximity effect). The results showed that multi-finger force stabilizing synergies dominate during involuntary reactions to externally imposed finger force changes. Within the referent configuration hypothesis, the data suggest that the instruction "not to interfere" leads to adjustments of the referent coordinates of all the individual fingers.

Assisted reproduction in a patient with Klippel-Trenaunay syndrome: management of thrombophilia and consumptive coagulopathy

Klippel-Trenaunay Syndrome (KTS) is a rare, sporadic triad of congenital malformations involving an extensive port wine stain, soft tissue or bone hypertrophy and underlying venous and/or lymphatic malformation involving an extremity. Pregnancy is known to exacerbate KTS complications and can put women at increased obstetrical risk due to deep venous thrombosis and other thromboembolic events. Here we report a case of a patient with KTS who achieved a pregnancy through in vitro fertilization (IVF) using her own eggs and a gestational surrogate in the setting of hypercoagulability and chronic consumptive coagulopathy.

Diminished ovarian reserve in a woman with a balanced 13;21 translocation

OBJECTIVE

To present the a case of decreased ovarian reserve in a patient with a balanced 13;21 translocation.

DESIGN

Case report.

SETTING

Reproductive endocrinology and infertility practice in a university teaching hospital.

PATIENT(S)

A 33-year-old caucasian woman with primary infertility.

INTERVENTION(S)

Laboratory evaluation, hysterosalpingogram, karyotype analysis, semen analysis.

MAIN OUTCOME MEASURE(S)

Endocrinologic evaluation and genetic analysis.

RESULT(S)

A diagnosis of decreased ovarian reserve based upon laboratory evaluation with concomitant findings of a balanced translocation between the long arms of chromosomes 13 and 21.

CONCLUSION(S)

A diagnosis of primary infertility secondary to decreased ovarian reserve of unknown etiology, but with karyotype evidence of a balanced autosomal translocation and a familial history of early menopause, suggested possible roles of autosomal genes in mechanisms of ovarian follicular attrition.

Experimental set-up and sensory glove interface for microsurgery

One of the most fundamental prerequisites for successful microsurgery is thoughtful and adequate training. A combination of knowledge, technical skill, and decision making directly influences the surgical outcome. This study aims to analyse microsurgical hand coordinations quantitatively and to study the utility of a sensory glove interface in identifying the hand coordination patterns during microsurgery. A sensory glove interface used to measure the angular flexion—extension movements of the major interphalangeal joints of the hand, the grasp pressure, and the relative hand movements has been developed. Experiments of two suturing techniques were conducted with five experienced microsurgeons, and microsurgery practice was examined. The custom sensory glove interface required both signal conditioning and amplification which was directly interfaced with a custom-designed LABView software code. The sensory glove interface was calibrated using regression techniques and the set-up was validated using the Bland—Altman correlation technique.

The hand coordination patterns were analysed using principal-component analysis. Pareto plots showing the contribution of the principal components were analysed. The contributions of the first two sensory data components have also been compared with hand coordination studies. The temporal variations provided new insights into the underlying synergetic mechanisms and in particular the relation between different suture techniques on grasp pressure.

Ring chromosome 12 and severe oligospermia: a case report

OBJECTIVE

To describe an unusual presentation of ring chromosome 12, which manifested as severe azoospermia, resulting in male infertility.

DESIGN

Case report.

SETTING

In vitro fertilization center at a tertiary care hospital.

PATIENT(S)

A 27-year-old man diagnosed with unexplained azoospermia and ring chromosome 12 abnormality during a workup for primary infertility.

INTERVENTION(S)

In vitro fertilization with preimplantation genetic diagnosis.

MAIN OUTCOME MEASURE(S)

To confirm the importance of obtaining karyotypes in individuals with severe oligospermia.

RESULT(S)

Full-term pregnancy after IVF using donor sperm.

CONCLUSION(S)

Severe oligospermia and male infertility should be included in the spectrum of findings found in ring chromosome 12.

Epithelial apoptosis in mechanistically distinct methods of injury in the murine small intestine

Gut epithelial apoptosis is involved in the pathophysiology of multiple diseases. This study characterized intestinal apoptosis in three mechanistically distinct injuries with different kinetics of cell death. FVB/N mice were subjected to gamma radiation, Pseudomonas aeruginosa pneumonia or injection of monoclonal anti-CD3 antibody and sacrificed 4, 12, or 24 hours post-injury (n=10/time point). Apoptosis was quantified in the jejunum by hematoxylin and eosin (H&E), active caspase-3, terminal deoxynucleotidyl transferase dUTP-mediated nick end labeling (TUNEL), in situ oligoligation reaction (ISOL,) cytokeratin 18, and annexin V staining. Reproducible results were obtained only for H&E, active caspase-3, TUNEL and ISOL, which were quantified and compared against each other for each injury at each time point. Kinetics of injury were different with early apoptosis highest following radiation, late apoptosis highest following anti CD3, and more consistent levels following pneumonia. ISOL was the most consistent stain and was always statistically indistinguishable from at least 2 stains. In contrast, active caspase-3 demonstrated lower levels of apoptosis, while the TUNEL assay had higher levels of apoptosis in the most severely injured intestine regardless of mechanism of injury. H&E was a statistical outlier more commonly than any other stain. This suggests that regardless of mechanism or kinetics of injury, ISOL correlates to other quantification methods of detecting gut epithelial apoptosis more than any other method studied and compares favorably to other commonly accepted techniques of quantifying apoptosis in a large intestinal cross sectional by balancing sensitivity and specificity across a range of times and levels of death.

Impact of duration and dose of gonadotrophins on IVF outcomes

In order to examine whether the duration of the follicular phase and changes in daily gonadotrophin dosages impact IVF outcome, a retrospective analysis of women who underwent oocyte retrieval and fresh embryo transfer was performed. Among the parameters assessed were the number of days of gonadotrophin stimulation, changes in the daily dosage of gonadotrophins, total ampoules of gonadotrophins, embryo implantation rates, clinical pregnancy rates and ongoing pregnancy rates. The number of days of gonadotrophin stimulation, as determined by standard follicular size criteria did not appear to influence IVF outcomes. There was no significant difference in pregnancy rates between women who were stimulated for <9 days, 10-11 days or >12 days. When grouped by amount of starting daily dose of gonadotrophins there was a significant inverse relationship between gonadotrophin requirements and pregnancy rates (P=0.02). The data suggest that the success of an IVF cycle depends on the ovaries' ability to develop follicles of the appropriate size, not the speed at which the ovaries perform this function.

Ovarian cryopreservation with transposition of a contralateral ovary: a combined approach for fertility preservation in women receiving pelvic radiation

OBJECTIVE

To describe a technique of fertility preservation by ovarian transposition combined with ovarian cryopreservation in the setting of oncologic pelvic radiation for a reproductive age woman.

DESIGN

Case report.

SETTING

IVF center at a tertiary care hospital.

PATIENT(S)

Thirty-year-old nulligravid women who previously underwent lumbar spinal cord tumor debulking requested fertility preservation before pelvic radiation.

INTERVENTION(S)

Laparoscopic ovarian transposition with cryopreservation of the contralateral ovary.

MAIN OUTCOME MEASURE(S)

New technique in fertility preservation.

RESULT(S)

Laparoscopic surgery was used to evaluate, select, and remove a single ovary that then underwent cryopreservation. Transposition of the remaining ovary was subsequently successfully performed, placing it of out of the pelvis.

CONCLUSION(S)

The combination of ovarian cryopreservation and ovarian transposition may maximize future fertility options for women facing pelvic irradiation. This combined approach should be included among the options offered to reproductive age women before pelvic radiation.

Assessment of porous silicon substrate for well-characterised sensitive DNA chip implement

A biochip approach based on porous silicon as substrate is presented. The goal is to enhance the sensitivity of the biochip by increasing the specific surface area on the support. The elaboration of porous silicon layers has been optimized to guarantee good accessibility for large bio-molecule targets. Oligonucleotide probes are synthesised directly on the surface using phosphoramidite chemistry. The high specific surface area of porous silicon allows the direct characterisation, by infrared spectroscopy, of the porous layer formation and the functionalisation steps. The monolayer grafting and derivatisation protocol is additionally characterized by wettability and fluorescence microscopy. The surface modification of porous layers (i.e. thermal oxidation and chemical derivatisation) ensures the stability of the structure against strong chemical reagents used during the direct oligonucleotide synthesis. Finally the protocol is successfully transferred to a flat Si/SiO(2) substrate, and validated by biological target specific recognition during hybridisation tests. In particular, radioactive measurements show a 10-fold enhancement of the oligonucleotide surface density on the porous silicon substrate compared to the flat thermal silica.

Immobilisation of oligo-peptidic probes for microarray implementation: Characterisation by FTIR, Atomic Force Microscopy and 2D fluorescence

Proteomic microarrays show a wide range of applications for the investigation of DNA-protein, enzyme-substrate as well as protein-protein interactions. Among many challenges to build a viable "protein microarray", the surface chemistry that will allow to immobilised various proteins to retain their biological activity is of paramount importance. Here we report a chemical functionalisation method allowing immobilisation of oligo-peptides onto silica surface (porous silica, glass, thermal silicon dioxide). Substrates were first derivatised with a monofunctional silane allowing the elaboration of dense and uniform monolayers in highly reproducible way. Prior to the oligo-peptides grafting, this organic layer was functionalised with an amino-polyethyleneglycol. The coupling step of oligo-peptides onto functionalised supports is achieved through activation of the C-terminal function of the oligo-peptides. Chemical surface modifications were followed by FTIR spectroscopy, AFM measurements and fluorescence scanning microscopy. A systematic study of the oligo-peptide grafting conditions (time, concentration, solvent) was carried out to optimise this step. The oligo-peptides grafting strategy implemented in this work ensure a covalent and oriented grafting of the oligo-peptides. This orientation is ensured through the use of fully protected peptide except the terminal primary amine. The immobilized peptides will be then deprotected before biological recognition. This strategy is crucial to retain the biological activity of thousands of oligo-probes assessed on a microarray.