Feasibility Analysis of Ultrasound-Guided Placement of Tunneled Hemodialysis Catheters.

Introduction: Radiographic fluoroscopy is the current standard for placement of tunneled central venous catheters (CVCs) for hemodialysis. Radiographic fluoroscopy requires structural and personnel infrastructure and exposes the patient to ionizing radiation. Here, we investigate the feasibility of solely ultrasound-guided placement of tunneled central venous dialysis catheters (USCVCs). Methods: We evaluated prospectively collected single-center data regarding safety and catheter function of 134 consecutive patients who underwent USCVC implantation between 2020 and 2021. We used the inset guidewire to visualize the position of the catheter tip. In the case of inadequate visibility by ultrasound, we used intracardiac electrocardiography (ECG) recording or agitated saline. A total of 1844 catheter days were assessed. The optimal CVC position was defined as being within the upper right atrium (URA) and middle to deep right atrium. Results: Of the 134 USCVCs, 87% were placed on the right side. The primary success rate for optimal tip position and catheter function was 98%. Of the USCVCs, 97% were placed solely by ultrasound. Regarding positioning, 6% were in the vena cava superior zone, 70% in the URA and 24% in the middle to deep right atrium, resulting in a rate of 94% with optimal positioning. Effective blood flow averaged 292 ± 39 ml/min. There were no immediate procedure-associated complications. Conclusion: Placement of CVC for hemodialysis solely by ultrasound is an effective alternative to fluoroscopy-assisted placement.

Differential Activity of Orthosteric Agonists and Allosteric Modulators at Metabotropic Glutamate Receptor 7.

Metabotropic glutamate receptor 7 (mGlu7) is a G protein coupled receptor that has demonstrated promise as a therapeutic target across a number of neurologic and psychiatric diseases. Compounds that modulate the activity of mGlu7, such as positive and negative allosteric modulators, may represent new therapeutic strategies to modulate receptor activity. The endogenous neurotransmitter associated with the mGlu receptor family, glutamate, exhibits low efficacy and potency in activating mGlu7, and surrogate agonists, such as the compound L-(+)-2-Amino-4-phosphonobutyric acid (L-AP4), are often used for receptor activation and compound profiling. To understand the implications of the use of such agonists in the development of positive allosteric modulators (PAMs), we performed a systematic evaluation of receptor activation using a system in which mutations can be made in either protomer of the mGlu7 dimer; we employed mutations that prevent interaction with the orthosteric site as well as the G-protein coupling site of the receptor. We then measured increases in calcium levels downstream of a promiscuous G protein to assess the effects of mutations in one of the two protomers in the presence of two different agonists and three positive allosteric modulators. Our results reveal that distinct PAMs, for example N-[3-Chloro-4-[(5-chloro-2-pyridinyl)oxy]phenyl]-2-pyridinecarboxamide (VU0422288) and 3-(2,3-Difluoro-4-methoxyphenyl)-2,5-dimethyl-7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidine (VU6005649), do exhibit different maximal levels of potentiation with L-AP4 versus glutamate, but there appear to be common stable receptor conformations that are shared among all of the compounds examined here. SIGNIFICANCE STATEMENT: This manuscript describes the systematic evaluation of the mGlu7 agonists glutamate and L-(+)-2-Amino-4-phosphonobutyric acid (L-AP4) in the presence and absence of three distinct potentiators examining possible mechanistic differences. These findings demonstrate that mGlu7 potentiators display subtle variances in response to glutamate versus L-AP4.

Transcriptomic Characterization of Inhalation Phosphine Toxicity in Adult Male Sprague-Dawley Rats.

Phosphine (PH3) is a highly toxic, corrosive, flammable, heavier-than-air gas that is a commonly used fumigant. When used as a fumigant, PH3 can be released from compressed gas tanks or produced from commercially available metal phosphide tablets. Although the mechanism of toxicity is unclear, PH3 is thought to be a metabolic poison. PH3 exposure induces multiorgan toxicity, and no effective antidotes or therapeutics have been identified. Current medical treatment consists largely of supportive care and maintenance of cardiovascular function. To better characterize the mechanism(s) driving PH3-induced toxicity, we have performed transcriptomic analysis on conscious adult male Sprague-Dawley rats following whole-body inhalation exposure to phosphine gas at various concentration-time products. PH3 exposure induced concentration- and time-dependent changes in gene expression across multiple tissues. These gene expression changes were mapped to pathophysiological responses using molecular pathway analysis. Toxicity pathways indicative of cardiac dysfunction, cardiac arteriopathy, and cardiac enlargement were identified. These cardiotoxic responses were linked to apelin-mediated cardiomyocyte and cardiac fibroblast signaling pathways. Evaluation of gene expression changes in blood revealed alterations in pathways associated with the uptake, transport, and utilization of iron. Altered erythropoietin signaling was also observed in the blood. Upstream regulator analysis identified several therapeutics predicted to counteract PH3-induced gene expression changes. These include antihypertensive drugs (losartan, candesartan, and prazosin) and therapeutics to reduce pathological cardiac remodeling (curcumin and TIMP3). This transcriptomics study has characterized molecular pathways involved in PH3-induced cardiotoxicity. These data will aid in elucidating a precise mechanism of toxicity for PH3 and guide the development of effective medical countermeasures for PH3-induced toxicity.

Regulation and functional consequences of mGlu4 RNA editing.

Metabotropic glutamate receptor 4 (mGlu4) is one of eight mGlu receptors within the Class C G protein-coupled receptor superfamily. mGlu4 is primarily localized to the presynaptic membrane of neurons where it functions as an auto and heteroreceptor controlling synaptic release of neurotransmitter. mGlu4 is implicated in numerous disorders and is a promising drug target; however, more remains to be understood about its regulation and pharmacology. Using high-throughput sequencing, we have validated and quantified an adenosine-to-inosine (A-to-I) RNA editing event that converts glutamine 124 to arginine in mGlu4; additionally, we have identified a rare but novel K129R site. Using an in vitro editing assay, we then validated the pre-mRNA duplex that allows for editing by ADAR enzymes and predicted its conservation across the mammalian species. Structural modeling of the mGlu4 protein predicts the Q124R substitution to occur in the B helix of the receptor that is critical for receptor dimerization and activation. Interestingly, editing of a receptor homodimer does not disrupt G protein activation in response to the endogenous agonist, glutamate. Using an assay designed to specifically measure heterodimer populations at the surface, however, we found that Q124R substitution decreased the propensity of mGlu4 to heterodimerize with mGlu2 and mGlu7 Our study is the first to extensively describe the extent and regulatory factors of RNA editing of mGlu4 mRNA transcripts. In addition, we have proposed a novel functional consequence of this editing event that provides insights regarding its effects in vivo and expands the regulatory capacity for mGlu receptors.

Excluding Lung Tissue from the PTV during Internal Mammary Irradiation. A Safe Technique for OAR-Sparing?

The current study aims to determine whether exclusion of lung tissue from planning treatment volume (PTV) is a valid organ at risk (OAR)-sparing technique during internal mammary irradiation (IMNI). Twenty patients with left-sided breast cancer undergoing adjuvant radiotherapy including IMNI after mastectomy or lumpectomy with daily ConeBeam CT (CBCT; median n = 28) were enrolled in the current study. The daily dose distribution of the patients was estimated by recalculating treatment plans on CBCT-scans based on a standard PTV (PTV margin: 5mm-STD) and a modified PTV, which excluded overlapping lung tissue (ExLung). Using 3D-deformable dose accumulation, the dose coverage in the target volume was estimated in dependence of the PTV-margins. The estimated delivered dose in the IMN-CTV was significantly lower for the ExLung PTV compared to the STD PTV: ExLung: V95%: 76.6 ± 22.9%; V90%: 89.6 ± 13.2%, STD: V95%: 95.6 ± 7.4%; V90%: 99.1 ± 2.7%. Daily CBCT imaging cannot sufficiently compensate the anatomic changes and intrafraction movement throughout the treatment. Therefore, to ensure adequate delivery of the prescribed dose to the IMN-CTV, exclusion of lung tissue from the PTV to spare the OARs is not recommended.

Long-term Results of Differentiated Anatomic Reconstruction of Bicuspid Aortic Valves.

Importance: Bicuspid aortic valve (BAV) repair has been used in limited cohorts, but its long-term results in a large population are unknown. Objectives: To analyze the long-term stability of BAV repair for survival and the factors associated with repair failure and to evaluate whether a differentiated anatomic repair approach may improve repair stability. Design, Setting, and Participants: In this case series, 1024 patients underwent BAV repair for aortic regurgitation or aneurysm between October 1995 and June 2018, with a mean (SD) follow-up time of 56 (49) months and maximum follow-up of 271 months. Systematic modifications in technique based on anatomic principles were introduced in 2009 and applied for the last 727 patients. Data were acquired prospectively and analyzed retrospectively. Exposures: Repair of BAV with or without concomitant aortic replacement, as well as postoperative clinical and echocardiographic follow-up. Main Outcomes and Measures: Survival and incidence of reoperation or recurrent aortic regurgitation, as well as factors associated with valve repair failure. Results: Among the 1024 patients in the study (920 male [89.8%]; mean [SD] age, 47 [13] years [range, 15-86 years]), the survival rate at 15 years was 82.1%. The cumulative incidence of reoperation was 30.7% (95% CI, 22.7%-38.7%) at 15 years. Cusp calcification (subdistribution hazard ratio, 1.78; 95% CI, 1.14-2.77; P = .01), asymmetric commissural orientation (subdistribution hazard ratio, 1.95; 95% CI, 1.02-3.72; P = .04), and use of a pericardial patch for cusp repair (subdistribution hazard ratio, 5.25; 95% CI, 3.52-7.82; P < .001) were associated with time to reoperation. At 10 years, the incidence of reoperation was significantly reduced among patients who received the anatomic repair concept compared with those who had undergone surgery in the earlier period (8.8% vs 24.6%; P < .001). Conclusions and Relevance: This study suggests that survival after BAV repair is excellent and that a large proportion of BAV repairs will remain stable. Repair stability can be markedly improved by an anatomic repair concept. Cusp calcification and the need for cusp repair using a patch remain the factors most strongly associated with valve failure. In those instances, valve replacement should be preferred.

Structure-Activity Relationships, Pharmacokinetics, and Pharmacodynamics of the Kir6.2/SUR1-Specific Channel Opener VU0071063.

Glucose-stimulated insulin secretion from pancreatic ß-cells is controlled by ATP-regulated potassium (KATP) channels composed of Kir6.2 and sulfonylurea receptor 1 (SUR1) subunits. The KATP channel-opener diazoxide is FDA-approved for treating hyperinsulinism and hypoglycemia but suffers from off-target effects on vascular KATP channels and other ion channels. The development of more specific openers would provide critically needed tool compounds for probing the therapeutic potential of Kir6.2/SUR1 activation. Here, we characterize a novel scaffold activator of Kir6.2/SUR1 that our group recently discovered in a high-throughput screen. Optimization efforts with medicinal chemistry identified key structural elements that are essential for VU0071063-dependent opening of Kir6.2/SUR1. VU0071063 has no effects on heterologously expressed Kir6.1/SUR2B channels or ductus arteriole tone, indicating it does not open vascular KATP channels. VU0071063 induces hyperpolarization of ß-cell membrane potential and inhibits insulin secretion more potently than diazoxide. VU0071063 exhibits metabolic and pharmacokinetic properties that are favorable for an in vivo probe and is brain penetrant. Administration of VU0071063 inhibits glucose-stimulated insulin secretion and glucose-lowering in mice. Taken together, these studies indicate that VU0071063 is a more potent and specific opener of Kir6.2/SUR1 than diazoxide and should be useful as an in vitro and in vivo tool compound for investigating the therapeutic potential of Kir6.2/SUR1 expressed in the pancreas and brain.

Endoscopic full-thickness resection for early colorectal cancer.

BACKGROUND AND AIMS: Current international guidelines recommend endoscopic resection for T1 colorectal cancer (CRC) with low-risk histology features and oncologic resection for those at high risk of lymphatic metastasis. Exact risk stratification is therefore crucial to avoid under-treatment as well as over-treatment. Endoscopic full-thickness resection (EFTR) has shown to be effective for treatment of non-lifting benign lesions. In this multicenter, retrospective study we aimed to evaluate efficacy, safety, and clinical value of EFTR for early CRC. METHODS: Records of 1234 patients undergoing EFTR for various indications at 96 centers were screened for eligibility. A total of 156 patients with histologic evidence of adenocarcinoma were identified. This cohort included 64 cases undergoing EFTR after incomplete resection of a malignant polyp (group 1) and 92 non-lifting lesions (group 2). Endpoints of the study were: technical success, R0-resection, adverse events, and successful discrimination of high-risk versus low-risk tumors. RESULTS: Technical success was achieved in 144 out of 156 (92.3%). Mean procedural time was 42 minutes. R0 resection was achieved in 112 of 156 (71.8%). Subgroup analysis showed a R0 resection rate of 87.5% in Group 1 and 60.9% in Group 2 (P < .001). Severe procedure-related adverse events were recorded in 3.9% of patients. Discrimination between high-risk versus low-risk tumor was successful in 155 of 156 cases (99.3%). In Group 1, 84.1% were identified as low-risk lesions, whereas 16.3% in group 2 had low-risk features. In total, 53 patients (34%) underwent oncologic resection due to high-risk features whereas 98 patients (62%) were followed endoscopically. CONCLUSIONS: In early colorectal cancer, EFTR is technically feasible and safe. It allows exact histological risk stratification and can avoid surgery for low-risk lesions. Prospective studies are required to further define indications for EFTR in malignant colorectal lesions and to evaluate long-term outcome.

Two decades of experience with root remodeling and valve repair for bicuspid aortic valves.

OBJECTIVE: Bicuspid aortic valve anatomy is associated with ascending aortic aneurysm in approximately 50% of individuals and may lead to severe aortic regurgitation with aortic dilatation. Both entities may be treated by valve repair and root remodeling. The objective was to review the cumulative experience of 20 years. METHODS: Between November 1995 and December 2015, 357 patients (324 male; age 10-80 years; mean, 49 ± 13 years) underwent combined bicuspid aortic valve repair and root remodeling. Aortic regurgitation was relevant in 265 cases; the main indications for surgery were aortic regurgitation (n = 241), aortic aneurysm (n = 102), and acute dissection (n = 9). In 225 instances, a suture annuloplasty was added. Cusp calcification was present beyond the raphe in 52 cases, and an autologous pericardial patch was implanted for partial cusp replacement in 39 cases. All patients were followed. Follow-up was 97.8% complete with a mean of 57 ± 51 months (median, 39 months). RESULTS: Two patients died (hospital mortality 0.6%), and survival at 15 years was 81%. Reoperation became necessary for recurrent aortic regurgitation in 24 patients; 6 patients underwent reoperation for stenosis. Cumulative incidence of reoperation at 15 years was 21.7%. Cusp calcification and the use of a pericardial patch for cusp reconstruction were associated with time to reoperation (P = .002). CONCLUSIONS: Repair of the bicuspid aortic valve combined with root remodeling leads to excellent 10- and 15-year results. Cusp calcification and the need for partial cusp replacement are associated with valve failure.

Suture Annuloplasty Significantly Improves the Durability of Bicuspid Aortic Valve Repair.

BACKGROUND: Isolated repair of the regurgitant bicuspid aortic valve (BAV) has yielded suboptimal durability, with annular dilatation being important risk factor for recurrent aortic regurgitation. We hypothesized that adding a suture annuloplasty (SA) should lead to improved repair stability. METHODS: Between July 1999 and September 2014, 268 patients (mean age, 41 ± 13 years, 249 male) underwent isolated BAV repair. From January 2009 to September 2014, 164 consecutive patients (study group) underwent SA using either braided polyester (n = 37) or expanded polytetrafluorethylene (PTFE) (n = 127). Patients who underwent surgery prior to January 2009 served as controls (n = 104). All patients were followed (98.9% complete, 1 week to 181 months). RESULTS: Annular size was larger in the study group (p < 0.001) and age was lower (p < 0.001). There were no differences between the groups regarding other clinical data. Hospital mortality was 0.7% (n = 2), 10-year survival was 94.2%. Thirty-six patients required valve-related reoperations (8 days to 94 months postoperatively; controls = 32, study = 4). Complications related to SA (ventricular septal defect, interference with coronary artery) occurred in 6 (3.7%) patients, in 4 (10.8%) patients with polyester SA and in 2 (1.6%) patients with PTFE. In the control group freedom from reoperation at 5 and 10 years was 73.2% and 63.7%, respectively. With SA, 5-year stability was significantly improved to 92.6% (p = 0.0006); it was 96.7% for PTFE versus 83.5% for polyester SA (p = 0.0132). CONCLUSIONS: Annular dilatation is a risk factor for failure after repair of regurgitant BAV. Its elimination through the use of SA significantly improves repair stability. With PTFE as material for SA optimal repair stability and minimal local complications are achieved.

Stx1 prophage excision in Escherichia coli strain PA20 confers strong curli and biofilm formation by restoring native mlrA.

Prophage insertions in Escherichia coli O157:H7 mlrA contribute to the low expression of curli fimbriae and biofilm observed in many clinical isolates. Varying levels of CsgD-dependent curli/biofilm expression are restored to strains bearing prophage insertions in mlrA by mutation of regulatory genes affecting csgD Our previous study identified strong biofilm- and curli-producing variants in O157:H7 cultures that had lost the mlrA-imbedded prophage characteristic of the parent population, suggesting prophage excision as a mechanism for restoring biofilm properties. In this study, we compared genomic, transcriptomic and phenotypic properties of parent strain PA20 (stx1, stx2) and its prophage-cured variant, 20R2R (stx2), and confirmed the mechanism underlying the differences in biofilm formation.

Characterization of visual pigments, oil droplets, lens and cornea in the whooping crane Grus americana.

Vision has been investigated in many species of birds, but few studies have considered the visual systems of large birds and the particular implications of large eyes and long-life spans on visual system capabilities. To address these issues we investigated the visual system of the whooping crane Grus americana (Gruiformes, Gruidae), which is one of only two North American crane species. It is a large, long-lived bird in which UV sensitivity might be reduced by chromatic aberration and entrance of UV radiation into the eye could be detrimental to retinal tissues. To investigate the whooping crane visual system we used microspectrophotometry to determine the absorbance spectra of retinal oil droplets and to investigate whether the ocular media (i.e. the lens and cornea) absorb UV radiation. In vitro expression and reconstitution was used to determine the absorbance spectra of rod and cone visual pigments. The rod visual pigments had wavelengths of peak absorbance (λmax) at 500 nm, whereas the cone visual pigment λmax values were determined to be 404 nm (SWS1), 450 nm (SWS2), 499 nm (RH2) and 561 nm (LWS), similar to other characterized bird visual pigment absorbance values. The oil droplet cut-off wavelength (λcut) values similarly fell within ranges recorded in other avian species: 576 nm (R-type), 522 nm (Y-type), 506 nm (P-type) and 448 nm (C-type). We confirm that G. americana has a violet-sensitive visual system; however, as a consequence of the λmax of the SWS1 visual pigment (404 nm), it might also have some UV sensitivity.

Peptide-conjugated glass slides for selective capture and purification of diagnostic cells: Applications in urine cytology.

Obtaining a clear view of the cells of interest in diagnostic cytology can be challenging when specimens are contaminated with blood or other obscuring cells. In this study, we present a powerful technique for the selective capture of diagnostic epithelial cells directly on a microscope slide, highlighting its applications in urine cytology and immunocytochemistry (ICC). Using phage-display biopanning, we identified and synthesized a series of peptides that bind with high affinity to urothelial cells but not blood cells. We developed methods for conjugating the peptides to glass slides, and we used these slides to selectively capture both normal and cancerous epithelial cells from urine contaminated with blood cells. Unlike non-selective microscope slides, the peptide-conjugated slides selectively retained the cells of interest, recovering up to 75% of urothelial cells, while up to 98% of blood cells were washed away. The slides are compatible with Papanicolaou and hematoxylin and eosin (H&E) staining for cytology preparations, as well as ICC for detecting membrane-associated and nuclear cancer markers. We successfully detected the expression of carcinoembryonic antigen and survivin, two commonly measured bladder cancer markers. In addition to bladder cancer diagnostics, this technology has broad applications for increasing the quality of sample preparations in slide-based diagnostic testing.

Phage insertion in mlrA and variations in rpoS limit curli expression and biofilm formation in Escherichia coli serotype O157: H7.

Biofilm formation in Escherichia coli is a tightly controlled process requiring the expression of adhesive curli fibres and certain polysaccharides such as cellulose. The transcriptional regulator CsgD is central to biofilm formation, controlling the expression of the curli structural and export proteins and the diguanylate cyclase adrA, which indirectly activates cellulose production. CsgD itself is highly regulated by two sigma factors (RpoS and RpoD), multiple DNA-binding proteins, small regulatory RNAs and several GGDEF/EAL proteins acting through c-di-GMP. One such transcription factor MlrA binds the csgD promoter to enhance the RpoS-dependent transcription of csgD. Bacteriophage, often carrying the stx1 gene, utilize an insertion site in the proximal mlrA coding region of E. coli serotype O157 : H7 strains, and the loss of mlrA function would be expected to be the major factor contributing to poor curli and biofilm expression in that serotype. Using a bank of 55 strains of serotype O157 : H7, we investigated the consequences of bacteriophage insertion. Although curli/biofilm expression was restored in many of the prophage-bearing strains by a wild-type copy of mlrA on a multi-copy plasmid, more than half of the strains showed only partial or no complementation. Moreover, the two strains carrying an intact mlrA were found to be deficient in biofilm formation. However, RpoS mutations that attenuated or inactivated RpoS-dependent functions such as biofilm formation were found in >70 % of the strains, including the two strains with an intact mlrA. We conclude that bacteriophage interruption of mlrA and RpoS mutations provide major obstacles limiting curli expression and biofilm formation in most serotype O157 : H7 strains.

Phenotypic and genotypic characterization of biofilm forming capabilities in non-O157 Shiga toxin-producing Escherichia coli strains.

The biofilm life style helps bacteria resist oxidative stress, desiccation, antibiotic treatment, and starvation. Biofilm formation involves a complex regulatory gene network controlled by various environmental signals. It was previously shown that prophage insertions in mlrA and heterogeneous mutations in rpoS constituted major obstacles limiting biofilm formation and the expression of extracellular curli fibers in strains of Escherichia coli serotype O157:H7. The purpose of this study was to test strains from other important serotypes of Shiga toxin-producing E. coli (STEC) (O26, O45, O103, O111, O113, O121, and O145) for similar regulatory restrictions. In a small but diverse collection of biofilm-forming and non-forming strains, mlrA prophage insertions were identified in only 4 of the 19 strains (serotypes O103, O113, and O145). Only the STEC O103 and O113 strains could be complemented by a trans-copy of mlrA to restore curli production and Congo red (CR) dye affinity. RpoS mutations were found in 5 strains (4 serotypes), each with low CR affinity, and the defects were moderately restored by a wild-type copy of rpoS in 2 of the 3 strains attempted. Fourteen strains in this study showed no or weak biofilm formation, of which 9 could be explained by prophage insertions or rpoS mutations. However, each of the remaining five biofilm-deficient strains, as well as the two O145 strains that could not be complemented by mlrA, showed complete or nearly complete lack of motility. This study indicates that mlrA prophage insertions and rpoS mutations do limit biofilm and curli expression in the non-serotype O157:H7 STEC but prophage insertions may not be as common as in serotype O157:H7 strains. The results also suggest that lack of motility provides a third major factor limiting biofilm formation in the non-O157:H7 STEC. Understanding biofilm regulatory mechanisms will prove beneficial in reducing pathogen survival and enhancing food safety.

Opsin evolution in damselfish: convergence, reversal, and parallel evolution across tuning sites.

The visual system plays a role in nearly every aspect of an organism's life history, and there is a direct link between visual pigment phenotypes and opsin genotypes. In previous studies of African cichlid fishes, we found evidence for positive selection among some opsins, with sequence variation greatest for opsins producing the shortest and longest wavelength visual pigments. In this study, we examined opsin evolution in the closely related damselfish family (Pomacentridae), a group of reef fishes that are distributed widely and have a documented fossil record of at least 50 million years (MY). We found increased functional variation in the protein sequences of opsins at the short- and long-wavelength ends of the visual spectrum, in agreement with the African cichlids, despite an order of magnitude difference in the ages of the two radiations. We also reconstructed amino acid substitutions across opsin tuning sites. These reconstructions indicated multiple instances of parallel evolution, at least one definitive case of convergent evolution, and one evolutionary reversal. Our findings show that the amino acids at spectral tuning sites are labile evolutionarily, and that the same codons evolve repeatedly. These findings emphasize that the aquatic light environment can shape opsin sequence evolution. They further show that phylogenetic approaches can provide important insights into the mechanisms by which natural selection "tinkers" with phenotypes.

Targeted delivery of vancomycin to Staphylococcus epidermidis biofilms using a fibrinogen-derived peptide.

This study reports on the use of a fibrinogen-derived peptide for the specific targeting and delivery of vancomycin to Staphylococcus epidermidis biofilms. One method by which S. epidermidis initially adheres to biomaterials uses the plasma protein fibrinogen as an intermediary, where the S. epidermidis surface protein SdrG binds to a short amino acid sequence near the amino terminus of the Bß chain of fibrinogen. We mimicked this binding interaction and demonstrated the use of a synthetic fibrinogen-based ß6-20 peptide to target and deliver vancomycin to S. epidermidis in vitro. The ß6-20 peptide was synthesized and labeled with a Nanogold probe, and its targeting capabilities were examined through the use of scanning electron microscopy. The Nanogold component was then replaced by vancomycin, utilizing a flexible, variable length poly(ethylene glycol) linker between the peptide and antibiotic to create the targeted vancomycin products, ß6-20-PEG(x) -VAN. Initial binding to surface adherent S. epidermidis was increased in a concentration-dependent manner relative to vancomycin for all equivalent concentrations ≥4 µg/mL, with targeted vancomycin content up to 22.9 times that of vancomycin alone. Retention of the targeted antibiotics was measured after an additional 24-h incubation period, revealing levels 1.3 times that of vancomycin. The results demonstrate the improved targeting and retention of vancomycin within a biofilm due to the incorporation of a specific targeting motif.

Disruption of Staphylococcus epidermidis biofilm formation using a targeted cationic peptide.

This study reports the use of a targeted cationic peptide with the ability to disrupt Staphylococcus epidermidis biofilm formation. Complications due to nosocomial infections of implanted medical devices pose a significant health risk to patients, with Staphylococcus epidermidis often implicated in the case of blood-contacting biomaterials. S. epidermidis virulence relies mainly on its ability to form a biofilm, the main component of which is polysaccharide intercellular adhesin (PIA). We utilized the synthetic ß6-20 peptide, known to specifically bind S. epidermidis, in order to deliver a cationic polylysine peptide (G(3)K(6)) to the bacterial surface and disrupt the charge-charge interactions needed for PIA retention and biofilm stability. The effects of the ß6-20-G(3)K(6) peptide on biofilm formation were assessed using optical density, fluorescently labeled wheat germ agglutinin, nucleic acid stain (SYTO 9), and a metabolic assay (XTT, 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide inner salt). Biofilms formed in the presence of ß6-20-G(3)K(6) peptide (100 µM) resulted in a 37.9% reduction in PIA content and a 17.5% reduction of adherent bacteria relative to biofilms grown in the absence of peptide. These studies demonstrate the targeting ability of the ß6-20 peptide towards biomaterial-adherent S. epidermidis, and highlight the potential for disrupting the early stages of biofilm formation.