Elasticity of polymers investigated by atomic-force microscopy

The elasticity of four different polymers, polystyrene (PS), polypropylene (PP), polytetrafluoroethylene (PTFE) and linear low-density polyethylene (LLDPE), and a self-assembled monolayer (SAM) of 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS) on a silicon oxide substrate perforated with circular holes prepared by polymer blend lithography was investigated by atomic force microscopy (AFM) by using two different methods: a static and a dynamic method, under nondry-air conditions and at ambient temperature. In the static method based on the method developed by Oliver and Pharr for rigid indenters [J. Mater. Res. 1992, 7, 1564-1583], the elastic modulus is determined from load-displacement curves obtained from indentations of the cantilever tip in the sample surface. The origin of the observed plastic and elastic deformation phases is explained. As indentations performed by cantilever tips differ from those done by rigid indenters, parameters, such as creep of the piezoelectric scanner, cold flow, thermal expansion of the sample and finite stiffness of the cantilever were investigated to make the results fit the theoretical model of Oliver and Pharr. The method was tested on PTFE and PS. In the dynamic method based on the AFM method devised by Herruzo et al. [Nat. Commun. 2014, 5, 3126], a more robust measurement method than the initial one is used to determine the frequency shifts necessary to compute the elastic modulus of samples. This method, that is based on the tracking of the two first flexural contact resonances, is especially well suited when measuring in ambient conditions. The normal force necessary for the measurements was assessed. The origin of the observed plastic and elastic deformation phases and the effect of the spring constant on the relation between the measured normal force and the displacement of the Z piezoelectric scanner in these phases are explained.The method was tested on LLDPE, PP, PS and the SAM. The storage modulus of LLDPE, PP, PS and FDTS was determined. The values for LLDPE, PP, and PS where compared with Young's modulus for bulk material. The value of the storage modulus for FDTS can be used as an estimation for the order of magnitude of Young's modulus of an FDTS monolayer.The measurements were performed with two controllers for scanning probe microscopes (SPM): Nanonis, a commercial controller from Specs (Zurich, Switzerland), and SAPHYR, whose hardware was developed by the Electronics Department of the Department of Physics of the University of Basel (Basel, Switzerland) in collaboration with Nanosurf (Liestal, Switzerland), a company specialized in SPM. The full software for the control of the different modules of SAPHYR was programmed in the LabVIEW environment during this work. The functions necessary to perform elasticity measurements with Oliver and Pharr's methods, but also to perform AFM imaging in general, were implemented. These functions are a Z controller for the control of the tip-sample surface distance, a scanner that can map all the necessary quantities (phase shifts, frequency shifts, dissipation, ...) and a Z spectroscopy function that can measure load-displacement curves.The initial method for the computation of phase shifts between an excitation signal and the cantilever response signal with SAPHYR lockin amplifiers was replaced by a more powerful algorithm developed by the author. In the initial method, the phase shift was determined from the real-time computation of ratio Y/X of the quadrature Y by the in-phase X components in the SAPHYR controller and the computation of arctan(Y/X) by the software for the control of SAPHYR. This algorithm, can compute arctan(Y/X) directly and precisely in the SAPHYR lockin amplifiers in real time. In addition, the algorithm overcomes the instabilities of the functioning of the initial phase-locked loops (PLLs) in SAPHYR based on the use of the approximation arctan(Y/X)~Y/X as a phase shift value, and due to magnitudes of phase shift and its variations greater than 0°, that occur, for example, when the cantilever tip picks up material or the sample surface elastic properties change. As this method is a good solution for the actual state of the art of the lockin and PLL development for AFM, my proposition for its patenting was accepted by the University of Basel. Finally, an analytical expression for the computation of the normal contact stiffness of a clamped cantilever with its tip in contact with the sample surface was established. This formula, derived from the equations based on Rabe's work and published by Hurley and Turner in J. Appl. Phys. 2007, 102, 033509, avoids the usual numerical determination of normal contact stiffness by the extrapolation method

Maximum tumor diameter adjusted to the risk profile predicts biochemical recurrence after radical prostatectomy

Currently, no consensus exists on the best method for tumor quantification in prostate cancer (PCA), and its prognostic value remains controversial. We evaluated how a newly defined maximum tumor diameter (MTD) might contribute to the prediction of biochemical recurrence (BCR) in a consecutive series of PCA patients treated with radical prostatectomy (RP). Patients with PCA who underwent RP without neoadjuvant therapy at a single center were included for analysis. MTD was defined as the largest diameter of all identified tumors in all three dimensions (i.e., length, width, or depth) of the prostate ("Basel technique”). Cox regression models addressed the association of MTD with BCR in three risk groups (low risk—prostate-specific antigen (PSA)  20ng/ml or pT3 or GS ≥ 8) and whole cohort. Within a median follow-up of 44months (interquartile range (IQR) 23-66), 48 patients (9.4%) in the intermediate-risk and high-risk groups experienced BCR. In multivariate Cox regression analysis, PSA, pathological stage (pT stage), GS, positive surgical margins (PSMs), and MTD > 19.5mm were independent predictors for BCR (p 24.5mm) was the only independent predictor of BCR in the intermediate-risk group (hazard ratio (HR) 9.933, 95% confidence interval (CI) 2.070-47.665; p < 0.05). MTD is an independent risk factor of BCR in PC patients after RP. The combination of the MTD with other well-known prognostic factors after RP may improve decision-making concerning follow-up intensity or adjuvant treatment

MAGE-C2/CT10 Protein Expression Is an Independent Predictor of Recurrence in Prostate Cancer

The cancer-testis (CT) family of antigens is expressed in a variety of malignant neoplasms. In most cases, no CT antigen is found in normal tissues, except in testis, making them ideal targets for cancer immunotherapy. A comprehensive analysis of CT antigen expression has not yet been reported in prostate cancer. MAGE-C2/CT-10 is a novel CT antigen. The objective of this study was to analyze extent and prognostic significance of MAGE-C2/CT10 protein expression in prostate cancer. 348 prostate carcinomas from consecutive radical prostatectomies, 29 castration-refractory prostate cancer, 46 metastases, and 45 benign hyperplasias were immunohistochemically analyzed for MAGE-C2/CT10 expression using tissue microarrays. Nuclear MAGE-C2/CT10 expression was identified in only 3.3% primary prostate carcinomas. MAGE-C2/CT10 protein expression was significantly more frequent in metastatic (16.3% positivity) and castration-resistant prostate cancer (17% positivity; p<0.001). Nuclear MAGE-C2/CT10 expression was identified as predictor of biochemical recurrence after radical prostatectomy (p = 0.015), which was independent of preoperative PSA, Gleason score, tumor stage, and surgical margin status in multivariate analysis (p<0.05). MAGE-C2/CT10 expression in prostate cancer correlates with the degree of malignancy and indicates a higher risk for biochemical recurrence after radical prostatectomy. Further, the results suggest MAGE-C2/CT10 as a potential target for adjuvant and palliative immunotherapy in patients with prostate cancer

Klf4 transcription factor is expressed in the cytoplasm of prostate cancer cells

BACKGROUND: Cancer initiation and progression might be driven by small populations of cells endowed with stem cell-like properties. Here we comparatively addressed the expression of genes encoding putative stemness regulators including c-Myc, Klf4, Nanog, Oct4A and Sox2 genes in benign prostatic hyperplasia (BPH) and prostate cancer (PCA). METHODS: Fifty-eight PCA and thirty-nine BPH tissues samples were used for gene expression analysis, as evaluated by quantitative real-time polymerase chain reaction (qRT-PCR). The expression of specific Klf4 isoforms was tested by conventional PCR. Klf4 specific antibodies were used for protein detection in a tissue microarray including 404 prostate samples. RESULTS: Nanog, Oct4A and Sox2 genes were comparably expressed in BPH and PCA samples, whereas c-Myc and Klf4 genes were expressed to significantly higher extents in PCA than in BPH specimens. Immunohistochemical studies revealed that Klf4 protein is detectable in a large majority of epithelial prostatic cells, irrespective of malignant transformation. However, in PCA, a predominantly cytoplasmic location was observed, consistent with the expression of a differentially spliced Klf4α isoform. CONCLUSION: Klf4 is highly expressed at gene and protein level in BPH and PCA tissues but a cytoplasmic location of the specific gene product is predominantly detectable in malignant cells. Klf4 location might be of critical relevance to steer its functions during oncogenesis

Two-Dimensional Carrier Profiling on Lightly Doped n-Type 4H-SiC Epitaxially Grown Layers

Electronically active dopant profiles of epitaxially grown n-type 4H-SiC calibration layer structures with concentrations ranging from 3.1015 cm-3 to 1·1019 cm-3 have been investigated by non-contact Scanning Probe Microscopy (SPM) methods. We have shown that Kelvin Probe Force Microscopy (KPFM) and Electrostatic Force Microscopy (EFM) are capable of resolving two-dimensional carrier maps in the low doping concentration regime with nanoscale spatial resolution. Furthermore, different information depths of this wide band gap semiconductor material could be assessed due to the inherent properties of each profiling method. We additionally observed a resolution enhancement under laser illumination which we explain by reduced band-bending conditions. To gauge our SPM signals, we utilized epitaxially grown layers which were calibrated, in terms of dopant concentration, by C-V measurements

Estrogen receptor β expression and androgen receptor phosphorylation correlate with a poor clinical outcome in hormone-naive prostate cancer and are elevated in castration-resistant disease

Patients with advanced prostate cancer (PC) are usually treated with androgen withdrawal. While this therapy is initially effective, nearly all PCs become refractory to it. As hormone receptors play a crucial role in this process, we constructed a tissue microarray consisting of PC samples from 107 hormone-naïve (HN) and 101 castration-resistant (CR) PC patients and analyzed the androgen receptor (AR) gene copy number and the protein expression profiles of AR, Serin210-phosphorylated AR (pAR(210)), estrogen receptor (ER)β, ERα and the proliferation marker Ki67. The amplification of the AR gene was virtually restricted to CR PC and was significantly associated with increased AR protein expression (P<0.0001) and higher tumor cell proliferation (P=0.001). Strong AR expression was observed in a subgroup of HN PC patients with an adverse prognosis. In contrast, the absence of AR expression in CR PC was significantly associated with a poor overall survival. While pAR(210) was predominantly found in CR PC patients (P<0.0001), pAR(210) positivity was observed in a subgroup of HN PC patients with a poor survival (P<0.05). Epithelial ERα expression was restricted to CR PC cells (9%). ERβ protein expression was found in 38% of both HN and CR PCs, but was elevated in matched CR PC specimens. Similar to pAR(210), the presence of ERβ in HN patients was significantly associated with an adverse prognosis (P<0.005). Our results strongly suggest a major role for pAR(210) and ERβ in HN PC. The expression of these markers might be directly involved in CR tumor growth