Multiomics approach to profiling Sertoli cell maturation during development of the spermatogonial stem cell niche.

Spermatogonial stem cells (SSCs) are the basis of spermatogenesis, a complex process supported by a specialized microenvironment, called the SSC niche. Postnatal development of SSCs is characterized by distinct metabolic transitions from prepubertal to adult stages. An understanding of the niche factors that regulate these maturational events is critical for the clinical application of SSCs in fertility preservation. To investigate the niche maturation events that take place during SSC maturation, we combined different '-omics' technologies. Serial single cell RNA sequencing analysis revealed changes in the transcriptomes indicative of niche maturation that was initiated at 11 years of age in humans and at 8 weeks of age in pigs, as evident by Monocle analysis of Sertoli cells and peritubular myoid cell (PMC) development in humans and Sertoli cell analysis in pigs. Morphological niche maturation was associated with lipid droplet accumulation, a characteristic that was conserved between species. Lipidomic profiling revealed an increase in triglycerides and a decrease in sphingolipids with Sertoli cell maturation in the pig model. Quantitative (phospho-) proteomics analysis detected the activation of distinct pathways with porcine Sertoli cell maturation. We show here that the main aspects of niche maturation coincide with the morphological maturation of SSCs, which is followed by their metabolic maturation. The main aspects are also conserved between the species and can be predicted by changes in the niche lipidome. Overall, this knowledge is pivotal to establishing cell/tissue-based biomarkers that could gauge stem cell maturation to facilitate laboratory techniques that allow for SSC transplantation for restoration of fertility.

Metabolic transitions define spermatogonial stem cell maturation.

STUDY QUESTION: Do spermatogonia, including spermatogonial stem cells (SSCs), undergo metabolic changes during prepubertal development? SUMMARY ANSWER: Here, we show that the metabolic phenotype of prepubertal human spermatogonia is distinct from that of adult spermatogonia and that SSC development is characterized by distinct metabolic transitions from oxidative phosphorylation (OXPHOS) to anaerobic metabolism. WHAT IS KNOWN ALREADY: Maintenance of both mouse and human adult SSCs relies on glycolysis, while embryonic SSC precursors, primordial germ cells (PGCs), exhibit an elevated dependence on OXPHOS. Neonatal porcine SSC precursors reportedly initiate a transition to an adult SSC metabolic phenotype at 2 months of development. However, when and if such a metabolic transition occurs in humans is ambiguous. STUDY DESIGN, SIZE, DURATION: To address our research questions: (i) we performed a meta-analysis of publicly available and newly generated (current study) single-cell RNA sequencing (scRNA-Seq) datasets in order to establish a roadmap of SSC metabolic development from embryonic stages (embryonic week 6) to adulthood in humans (25 years of age) with a total of ten groups; (ii) in parallel, we analyzed single-cell RNA sequencing datasets of isolated pup (n = 3) and adult (n = 2) murine spermatogonia to determine whether a similar metabolic switch occurs; and (iii) we characterized the mechanisms that regulate these metabolic transitions during SSC maturation by conducting quantitative proteomic analysis using two different ages of prepubertal pig spermatogonia as a model, each with four independently collected cell populations. PARTICIPANTS/MATERIALS, SETTING, METHODS: Single testicular cells collected from 1-year, 2-year and 7-year-old human males and sorted spermatogonia isolated from 6- to 8-day (n = 3) and 4-month (n = 2) old mice were subjected to scRNA-Seq. The human sequences were individually processed and then merged with the publicly available datasets for a meta-analysis using Seurat V4 package. We then performed a pairwise differential gene expression analysis between groups of age, followed by pathways enrichment analysis using gene set enrichment analysis (cutoff of false discovery rate < 0.05). The sequences from mice were subjected to a similar workflow as described for humans. Early (1-week-old) and late (8-week-old) prepubertal pig spermatogonia were analyzed to reveal underlying cellular mechanisms of the metabolic shift using immunohistochemistry, western blot, qRT-PCR, quantitative proteomics, and culture experiments. MAIN RESULTS AND THE ROLE OF CHANCE: Human PGCs and prepubertal human spermatogonia show an enrichment of OXPHOS-associated genes, which is downregulated at the onset of puberty (P < 0.0001). Furthermore, we demonstrate that similar metabolic changes between pup and adult spermatogonia are detectable in the mouse (P < 0.0001). In humans, the metabolic transition at puberty is also preceded by a drastic change in SSC shape at 11 years of age (P < 0.0001). Using a pig model, we reveal that this metabolic shift could be regulated by an insulin growth factor-1 dependent signaling pathway via mammalian target of rapamycin and proteasome inhibition. LARGE SCALE DATA: New single-cell RNA sequencing datasets obtained from this study are freely available through NCBI GEO with accession number GSE196819. LIMITATIONS, REASONS FOR CAUTION: Human prepubertal tissue samples are scarce, which led to the investigation of a low number of samples per age. Gene enrichment analysis gives only an indication about the functional state of the cells. Due to limited numbers of prepubertal human spermatogonia, porcine spermatogonia were used for further proteomic and in vitro analyses. WIDER IMPLICATIONS OF THE FINDINGS: We show that prepubertal human spermatogonia exhibit high OXHPOS and switch to an adult-like metabolism only after 11 years of age. Prepubescent cancer survivors often suffer from infertility in adulthood. SSC transplantation could provide a powerful tool for the treatment of infertility; however, it requires high cell numbers. This work provides key insight into the dynamic metabolic requirements of human SSCs across development that would be critical in establishing ex vivo systems to support expansion and sustained function of SSCs toward clinical use. STUDY FUNDING/COMPETING INTEREST(S): This work was funded by the NIH/NICHD R01 HD091068 and NIH/ORIP R01 OD016575 to I.D. K.E.O. was supported by R01 HD100197. S.K.M. was supported by T32 HD087194 and F31 HD101323. The authors declare no conflict of interest.

Biomimetic reconstruction of the hematopoietic stem cell niche for in vitro amplification of human hematopoietic stem cells.

Hematopoietic stem cell transplantation is successfully applied since the late 1950s; however, its efficacy still needs to be increased. A promising strategy is to transplant high numbers of pluripotent hematopoietic stem cells (HSCs). Therefore, an improved ex vivo culture system that supports proliferation and maintains HSC pluripotency would override possible limitations in cell numbers gained from donors. To model the natural HSC niche in vitro, we optimized the HSC medium composition with a panel of cytokines and valproic acid and used an artificial 3D bone marrow-like scaffold made of polydimethylsiloxane (PDMS). This 3D scaffold offered a suitable platform to amplify human HSCs in vitro and, simultaneously, to support their viability, multipotency and ability for self-renewal. Silicon oxide-covering of PDMS structures further improved amplification of CD34+ cells, although the conservation of naïve HSCs was better on non-covered 3D PDMS. Finally, we found that HSC cultivated on non-covered 3D PDMS generated most pluripotent colonies within colony forming unit assays. In conclusion, by combining biological and biotechnological approaches, we optimized in vitro HSCs culture conditions, resulting in improved amplification, multipotency maintenance and vitality of HSCs.

Testicular organoids to study cell-cell interactions in the mammalian testis.

BACKGROUND: Over the last ten years, three-dimensional organoid culture has garnered renewed interest, as organoids generated from primary cells or stem cells with cell associations and functions similar to organs in vivo can be a powerful tool to study tissue-specific cell-cell interactions in vitro. Very recently, a few interesting approaches have been put forth for generating testicular organoids for studying the germ cell niche microenvironment. AIM: To review different model systems that have been employed to study germ cell biology and testicular cell-cell interactions and discuss how the organoid approach can address some of the shortcomings of those systems. RESULTS AND CONCLUSION: Testicular organoids that bear architectural and functional similarities to their in vivo counterparts are a powerful model system to study cell-cell interactions in the germ cell niche. Organoids enable studying samples in humans and other large animals where in vivo experiments are not possible, allow modeling of testicular disease and malignancies and may provide a platform to design more precise therapeutic interventions.

Antibiotic resistant bacteria and resistance genes in biofilms in clinical wastewater networks.

Increasing isolation rates of resistant bacteria in the last years require identification of potential infection reservoirs in healthcare facilities. Especially the clinical wastewater network represents a potential source of antibiotic resistant bacteria. In this work, the siphons of the sanitary installations from 18 hospital rooms of two German hospitals were examined for antibiotic resistant bacteria and antibiotic residues including siphons of showers and washbasins and toilets in sanitary units of psychosomatic, haemato-oncological, and rehabilitation wards. In addition, in seven rooms of the haemato-oncological ward, the effect of 24 h of stagnation on the antibiotic concentrations and MDR (multi-drug-resistant) bacteria in biofilms was evaluated. Whereas no antibiotic residues were found in the psychosomatic ward, potential selective concentrations of piperacillin, meropenem and ciprofloxacin were detected at a rehabilitation ward and ciprofloxacin and trimethoprim were present at a haemato-oncology ward. Antibiotic resistant bacteria were isolated from the siphons of all wards, however in the psychosomatic ward, only one MDR strain with resistance to piperacillin, third generation cephalosporins and quinolones (3MRGN) was detected. In contrast, the other two wards yielded 11 carbapenemase producing MDR isolates and 15 3MRGN strains. The isolates from the haemato-oncological ward belonged mostly to two specific rare sequence types (ST) (P. aeruginosa ST823 and Enterobacter cloacae complex ST167). In conclusion, clinical wastewater systems represent a reservoir for multi-drug-resistant bacteria. Consequently, preventive and intervention measures should not start at the wastewater treatment in the treatment plant, but already in the immediate surroundings of the patient, in order to minimize the infection potential.

Identification of cholinergic chemosensory cells in mouse tracheal and laryngeal glandular ducts.

Specialized epithelial cells in the respiratory tract such as solitary chemosensory cells and brush cells sense the luminal content and initiate protective reflexes in response to the detection of potentially harmful substances. The majority of these cells are cholinergic and utilize the canonical taste signal transduction cascade to detect "bitter" substances such as bacterial quorum sensing molecules. Utilizing two different mouse strains reporting expression of choline acetyltransferase (ChAT), the synthesizing enzyme of acetylcholine (ACh), we detected cholinergic cells in the submucosal glands of the murine larynx and trachea. These cells were localized in the ciliated glandular ducts and were neither found in the collecting ducts nor in alveolar or tubular segments of the glands. ChAT expression in tracheal gland ducts was confirmed by in situ hybridization. The cholinergic duct cells expressed the brush cell marker proteins, villin and cytokeratin-18, and were immunoreactive for components of the taste signal transduction cascade (Gα-gustducin, transient receptor potential melastatin-like subtype 5 channel = TRPM5, phospholipase C(ß2)), but not for carbonic anhydrase IV. Furthermore, these cells expressed the bitter taste receptor Tas2r131, as demonstrated utilizing an appropriate reporter mouse strain. Our study identified a previously unrecognized presumptive chemosensory cell type in the duct of the airway submucosal glands that likely utilizes ACh for paracrine signaling. We propose that these cells participate in infection-sensing mechanisms and initiate responses assisting bacterial clearance from the lower airways.

A mechanism for cell motility by active polar gels.

We analyse a generic motility model, with the motility mechanism arising by contractile stress due to the interaction of myosin and actin. A hydrodynamic active polar gel theory is used to model the cytoplasm of a cell and is combined with a Helfrich-type model to account for membrane properties. The overall model allows consideration of the motility without the necessity for local adhesion. Besides a detailed numerical approach together with convergence studies for the highly nonlinear free boundary problem, we also compare the induced flow field of the motile cell with that of classical squirmer models and identify the motile cell as a puller or pusher, depending on the strength of the myosin-actin interactions.

[Pain therapy in patients with schizoaffective disorder and cancer]. / Schmerzbehandlung bei Patienten mit schizoaffektiver Psychose und Tumor.

We report on two patients with schizoaffective psychosis, cancer, and pain. However, it is not possible to make somatic or psychic disturbances alone responsible for the pain. In patients with current schizoaffective disorders, only administration of a combination of psychopharmaceutical and opioid agents is successful.

Feasibility of 6-month maintenance cetuximab after adjuvant concurrent chemoradiation plus cetuximab in squamous cell carcinoma of the head and neck.

BACKGROUND: Close resection margins < 5 mm (CM) or extra capsular extent at the lymph nodes (ECE) impair the prognosis of patients with squamous cell cancer of the head and neck (SCCHN) scheduled for adjuvant radiochemotherapy. We conducted a multicenter phase II study to investigate toxicity and efficacy of additional cetuximab administered concomitantly and as maintenance for the duration of 6 months following adjuvant radiochemotherapy., Ppreliminary results on feasibility and acute toxicity on skin and mucosa are presented in this article. METHODS: Patients with SCCHN following CM resection or with ECE were eligible for the study. In all, 61.6 Gy (1.8/2.0/2.2 Gy, days 1-36) were administered using an integrated boost intensity-modulated radiotherapy (IMRT) technique. Cisplatin (20 mg/m(2), days 1-5 and days 29-33) and 5-fluorouracil (5-FU) as continuous infusion (600 mg/m(2), days 1-5 + days 29-33) were given concurrently. Cetuximab was started 7 days prior to radiochemotherapy at 400 mg/m(2) followed by weekly doses of 250 mg/m(2). Maintenance cetuximab began after radiochemotherapy at 500 mg/m(2) every 2 weeks for 6 months. RESULTS: Of the 55 patients (46 male, 9 female, mean age 55.6, range 29-70 years) who finished radiochemotherapy, 50 were evaluable for acute toxicity concerning grade III/IV toxicities of skin and mucosa. Grade 3-4 (CTC 3.0) mucositis, radiation dermatitis, and skin reactions outside the radiation portals were documented for 46, 28, and 14 % of patients, respectively. One toxic death occurred (peritonitis at day 57). Cetuximab was terminated in 5 patients due to allergic reactions after the first application. In addition, 22 % of patients discontinued cetuximab within the last 2 weeks or at the end of radiochemotherapy. Of patients embarking on maintenance treatment, 80 % were still on cetuximab at 3 months and 63 % at 5 months. Concurrent and maintenance treatment with cetuximab could be administered as scheduled in 48 % of patients. CONCLUSION: Adjuvant radiochemotherapy with concomitant and maintenance cetuximab is feasible and acute toxicities are within the expected range. Compliance within the first 3-5 months is moderate.

Skeletal muscle uncoupling-induced longevity in mice is linked to increased substrate metabolism and induction of the endogenous antioxidant defense system.

Ectopic expression of uncoupling protein 1 (UCP1) in skeletal muscle (SM) mitochondria increases lifespan considerably in high-fat diet-fed UCP1 Tg mice compared with wild types (WT). To clarify the underlying mechanisms, we investigated substrate metabolism as well as oxidative stress damage and antioxidant defense in SM of low-fat- and high-fat-fed mice. Tg mice showed an increased protein expression of phosphorylated AMP-activated protein kinase, markers of lipid turnover (p-ACC, FAT/CD36), and an increased SM ex vivo fatty acid oxidation. Surprisingly, UCP1 Tg mice showed elevated lipid peroxidative protein modifications with no changes in glycoxidation or direct protein oxidation. This was paralleled by an induction of catalase and superoxide dismutase activity, an increased redox signaling (MAPK signaling pathway), and increased expression of stress-protective heat shock protein 25. We conclude that increased skeletal muscle mitochondrial uncoupling in vivo does not reduce the oxidative stress status in the muscle cell. Moreover, it increases lipid metabolism and reactive lipid-derived carbonyls. This stress induction in turn increases the endogenous antioxidant defense system and redox signaling. Altogether, our data argue for an adaptive role of reactive species as essential signaling molecules for health and longevity.

B domain containing Tenascin-C: a new urine marker for surveillance of patients with urothelial carcinoma of the urinary bladder?

BACKGROUND: ECM remodelling during tumorigenesis entails the re-occurrence of different Tn-C(L) splicing variants. In patients with urothelial carcinoma of the urinary bladder (UBC), B and C domain containing Tenascin-C (B(+) and C(+) Tn-C) urine levels were shown to be increased in case of muscle invasiveness. Thus, the present study was aimed at examining the ability of B(+) and C(+) Tn-C as potential urinary surveillance markers of UBC patients. METHODS: Urine levels of B(+) and C(+) Tn-C were determined by ELISA in 35 UBC patients during a 2 year follow-up period after therapy and related to clinical diagnosis and histological stage in 4 defined groups representing typical courses of disease. RESULTS: B(+) Tn-C levels showed significant differences between cases of tumour progression or regression. The urine levels of B(+) Tn-C could be used to discriminate between cases without tumour recurrence and such with tumour existence (cut-off value: 0.8 ng/ml) or between non-muscle invasive and muscle invasive tumour growth (cut-off value: 3.5 ng/ml). CONCLUSIONS: Progression of UBC with time is accompanied by significant changes in urinary levels of B(+) Tn-C. Urinary B(+) Tn-C can therefore be suggested as a valuable urine surveillance marker in UBC follow-up care.

In vitro inhibition of fungal activity by macrophage-mediated sequestration and release of encapsulated amphotericin B nanosupension in red blood cells.

The efficacy of antifungal treatment has been diminished by the biodistribution limitations of amphotericin B (AmB) due to its pharmacological profile, as well as the severe side effects it causes. A cellular drug-delivery system, which incorporates human erythrocytes (RBCs) loaded with an AmB nanosuspension (AmB-NS), is developed in order to improve antifungal treatment. AmB-NS encapsulation in RBCs is achieved by using hypotonic hemolysis, leading to intracellular AmB amounts of 3.81 +/- 0.47 pg RBC(-1) and an entrapment efficacy of 15-18%. Upon phagocytosis of AmB-NS-RBCs, leukocytes show a slow AmB release over ten days, and no alteration in cell viability. This results in an immediate, permanent inhibition of intra- and extracellular fungal activity. AmB-NS-RBC-leukocyte-mediated delivery of AmB is efficient in amounts 1000 times lower than the toxic dose. This drug-delivery method is effective for the transport of water-insoluble substances, such as AmB, and this warrants consideration for further testing.

Traumatic perforation of the trachea in two horses caused by orotracheal intubation.

Two of 348 horses that underwent gastrointestinal surgery under general anaesthesia developed perforations in their tracheas caused by the endotracheal tube. In one case the damage was probably caused when the horse was being moved from the induction room for surgery and excessive traction was exerted on the tube when the anaesthetic machine was moved too far ahead of the horse. The trachea of the other horse may have been damaged when it was intubated.

Use of Ir192 interstitial brachytherapy for an equine malignant dermal schwannoma.

A 10-year-old Hanoverian mare was evaluated for a right buccal swelling that recurred 3 months following surgical resection. Ultrasonographic examination showed a broadly pedunculated subcutaneous mass at the level of 106-109 and 406-409 cheek teeth associated with an erosive mucosal lesion on the inside of the cheek. Histological examination of a biopsy specimen revealed a well-demarcated, malignant, dermal schwannoma. Following subcutaneous placement of platinum coated Ir192 wires under general anaesthesia, low-dose radiation of 5 gray per day was delivered for 14 days. Short-term complications included loss of patency of the right nasolacrimal duct, erythema, dermatitis, leukotrichia and left-sided deviation of the muzzle. Ten months later, there has been no tumour recurrence. Findings suggest that the use of interstitial brachytherapy should be considered for a malignant, dermal schwannoma that has recurred or is not amenable to surgery.

Effects of an endurance and resistance exercise program on persistent cancer-related fatigue after treatment.

BACKGROUND: Fatigue is a relevant problem of cancer patients during and after treatment. Several studies have shown that exercise can improve quality of life and functional status of cancer patients undergoing chemo- or radiotherapy. However, there is a lack of information about the effects of this intervention on persistent cancer-related fatigue. Therefore, we assessed the effects of an exercise program on cancer-related fatigue after treatment. PATIENTS AND METHODS: A consecutive series of 32 cancer patients with mild to severe persistent fatigue [scores on the Brief Fatigue Inventory (BFI) > 25] participated in a 3-week exercise program consisting of endurance (30 min walking on a treadmill) and resistance/coordination exercises for the major muscle groups. Fatigue, mood, and anxiety were assessed with questionnaires and physical performance with a stress test before and after the program. RESULTS: At the end of the program, we observed a significant increase of physical performance (workload at the anaerobic threshold pre 61 +/- 26 W, post 78 +/- 31 W, P < 0.0001) and reduction of global fatigue (Functional Assessment of Cancer Therapy: pre 45.7 +/- 13.4, post 52.6 +/- 12.4, P < 0.0001; BFI: pre 37.9 +/- 18.3, post 31.2 +/-17.1, P < 0.001). However, no significant improvement of cognitive fatigue or reduction of anxiety was observed. CONCLUSIONS: A 3-week exercise program leads to a substantial improvement of physical performance and reduction of mental and physical fatigue in cancer patients after treatment. However, this intervention does not affect depression, anxiety, or cognitive fatigue.

Experimental analysis of retention forces of different magnetic devices for bone-anchored auricular facial prostheses.

The aim of this study was to determine which combination of differently designed magnetic abutments provides the best retention for an auricular prosthesis. The withdrawal forces of eight combinations of abutments were measured and results compared. There was a significantly higher withdrawal force in arrangements containing three magnets over only two. The highest withdrawal force was found in the combination of one telescopic magnet and two large spherical magnets (median: 7.69 N), whereas two telescopic magnets alone showed the lowest withdrawal force (3.41 N). The use of two conical magnets increased retention slightly, but the median retention force remained the same (3.41 N). The commonly used combination of two small spherical magnets and one telescopic magnet showed the lowest retention of combinations consisting of three magnets (4.94 N). There seems to be no difference in median withdrawal force if a conical magnet instead of a telescopic magnet is used. The withdrawal force at a 45 degrees angle was about 10% higher than the vertical force but the difference was not significant. The rupture force needed to tear the magnet completely out of the silicone was 240.6-519.7 N (mean 331.74 N) and therefore over 10 times higher than magnetic retention.

[Association between histopathologic type II synovitis and increased amounts of pyridinoline in synovial tissue samples in rheumatoid arthritis]. / Assoziation zwischen dem histopathologischen Synovialitis-Typ II und einem erhöhten Pyridinolin-Gehalt im Synovialgewebe bei rheumatoider Arthritis.

OBJECTIVE: To investigate the association between immunohistopathological and morphological features of synovitis in rheumatoid arthritis and the amounts of collagen degradation products pyridinoline and deoxypyridinoline in the synovial tissue and in body fluids in order to discover potential markers of erosive disease. METHODS: Histopathological analysis of synovial tissue samples from 22 patients with RA was performed according to the histopathologic scoring system of RA synovitis by P. Stiehl. Accordingly, the samples were (a) classified into type I synovitis, type II synovitis, or undifferentiated synovitis and were (b) characterized for local features of disease activity, including basic activity and actual activity. The contents of pyridinoline and deoxypyridinoline were measured in the synovial tissue, the synovial fluid, serum and urine by HPLC analysis. RESULTS: The amounts of pyridinoline in synovial tissue samples characterized by type II synovitis were 1.7-fold and 2.7-fold higher compared with those with type I synovitis and undifferentiated synovitis, respectively. In contrast, the content of deoxypyridinoline was not different between the histopathologic types of synovitis. At the same time, increased amounts of pyridinoline, but not deoxypyridinoline, were detected in synovial tissue samples with basic activity or actual activity grade II compared with synovial tissue samples with basic activity or actual activity grade I. The concentrations of both collagen degradation products in the synovial fluid, serum and urine did not differ between patients when they were analyzed either for histopathologic types of synovitis or local disease activity. CONCLUSION: The amount of cartilage collagen degradation product pyridinoline in synovial tissue is positively correlated with the histopathological grading of local disease activity. Furthermore, the increased amounts of pyridinoline in synovial tissue samples with type II synovitis suggest a more erosive course of RA in patients with this type of synovitis.

Characterization of a T-DNA insertion mutant for the protein import receptor atToc33 from chloroplasts.

In Arabidopsis thaliana, the Toc34 receptor component of the chloroplast import machinery is encoded by two independent but highly homologous genes, atToc33 and atToc34. We have isolated a T-DNA insertion mutant of atToc33 which is characterized by a pale phenotype, due to reductions in the levels of photosynthetic pigments, and alterations in protein composition. The latter involve not only chloroplast proteins but also some cytosolic polypeptides, including 14-3-3 proteins which, among other functions, have been proposed to be cytosolic targeting factors for nucleus-encoded chloroplast proteins. Within the chloroplast, many, though not all, proteins of the photosynthetic apparatus, as well as proteins not directly involved in photosynthesis, are found in significantly reduced amounts in the mutant. However, the accumulation of other chloroplast proteins is unaffected. This suggests that the atToc33 receptor is responsible for the import of a specific subset of nucleus-encoded chloroplast proteins. Supporting evidence for this conclusion was obtained by antisense repression of the atToc34 gene in the atToc33 mutant, which results in an exacerbation of the phenotype.

Improvement of surface acoustic wave gas and biosensor response characteristics using a capacitive coupling technique.

As for many other electronic devices and circuits, electrical contact to surface acoustic wave sensors is usually made using bonding wires. This technique is known to result in reliable contact under most conditions, but it does so with several disadvantages. First, electrical contact is not reversible, impeding replacement of sensor devices. Second, bonding wires are quite delicate and should not be exposed to high gas or liquid flows. Third, the presence of bonding wires may limit the potential to miniaturize a sensor housing or flow cell. Therefore, a capacitive coupling technique was developed to replace bonding wires. This permitted redesign of flow cells and sensor arrays, resulting in flow cell volumes of 80 microL to 60 nL. As a consequence, response times were reduced to 1-2 s in gas sensing and a few minutes in liquid sensing, respectively. At the same time, sensor devices can be easily replaced, and the system is less susceptible to malfunction.