Molecular Basis of XRN2-Deficient Cancer Cell Sensitivity to Poly(ADP-ribose) Polymerase Inhibition.

R-loops (RNA-DNA hybrids with displaced single-stranded DNA) have emerged as a potent source of DNA damage and genomic instability. The termination of defective RNA polymerase II (RNAPII) is one of the major sources of R-loop formation. 5'-3'-exoribonuclease 2 (XRN2) promotes genome-wide efficient RNAPII termination, and XRN2-deficient cells exhibit increased DNA damage emanating from elevated R-loops. Recently, we showed that DNA damage instigated by XRN2 depletion in human fibroblast cells resulted in enhanced poly(ADP-ribose) polymerase 1 (PARP1) activity. Additionally, we established a synthetic lethal relationship between XRN2 and PARP1. However, the underlying cellular stress response promoting this synthetic lethality remains elusive. Here, we delineate the molecular consequences leading to the synthetic lethality of XRN2-deficient cancer cells induced by PARP inhibition. We found that XRN2-deficient lung and breast cancer cells display sensitivity to two clinically relevant PARP inhibitors, Rucaparib and Olaparib. At a mechanistic level, PARP inhibition combined with XRN2 deficiency exacerbates R-loop and DNA double-strand break formation in cancer cells. Consistent with our previous findings using several different siRNAs, we also show that XRN2 deficiency in cancer cells hyperactivates PARP1. Furthermore, we observed enhanced replication stress in XRN2-deficient cancer cells treated with PARP inhibitors. Finally, the enhanced stress response instigated by compromised PARP1 catalytic function in XRN2-deficient cells activates caspase-3 to initiate cell death. Collectively, these findings provide mechanistic insights into the sensitivity of XRN2-deficient cancer cells to PARP inhibition and strengthen the underlying translational implications for targeted therapy.

Distal Femoral Valgus Resection Angle in Conventional Total Knee Arthroplasty - a CT Scanogram Study.

Objectives: In conventional total knee arthroplasty (TKA), the distal femur valgus resection angle (DFVA) is decided either by measuring the specific resection angle for each patient on preoperative anteroposterior hip-knee-ankle (HKA) weight-bearing radiograph or using a fixed resection angle of five to seven degrees, when such facilities are not available. This study aims to measure the DVFA in TKA patients using preoperative HKA non-weight-bearing computerized tomography (CT) scanogram scout films and determine its relation with preoperative coronal plane lower-limb deformities. Methods: In this retrospective radiological study, various measurements were performed on bilateral, preoperative hip-knee-ankle CT scanograms of 73 knee osteoarthritis patients who had presented for total knee replacement surgery using a standard protocol. The angle between the femoral anatomical axis and femoral mechanical axis was measured as the femoral mechanical anatomical angle (FMAA), which corresponds to the surgical DFVA. The angle between the femoral and tibial mechanical axes was measured as mechanical femorotibial angle (MFTA). The correlation between FMAA and MFTA was studied. Results: The mean FMAA for the study group was 6.45° (range 3° to 11°, SD 1.17°). The MFTA for the study group ranged from 24° varus to 14° valgus. The alignment was valgus in 14.4% (n=21), varus in 84.2% (n=123), and "0 degrees" in 1.3% (n=2). With valgus coronal alignment taken as positive and varus as negative, the Pearson's correlation coefficient for MFTA with FMAA was r = -0.5183 (p<0.001), indicating that valgus knees tended to have a smaller FMA angle and varus knees tended to have a larger FMA angle. Conclusion: In the non-availability of individualized measurements, in primary TKA, we recommend setting DFVA as five degrees for valgus deformities, six degrees for mild/moderate varus deformities (MFTA <15°) and seven degrees for severe varus deformities (MFTA > 15°).

Fate, transformation and toxicological implications of environmental diclofenac: Role of mineralogy and solar flux.

Diclofenac is an emerging surface water contaminant, yet the environmental impact of its degradation products remains elusive. The current study focuses on mineralogy-controlled diclofenac photo-degradation and its potential health impacts. Under irradiated conditions, we studied the effects of kaolinite, hematite, and anatase on diclofenac degradation. Our results showed that kaolinite doubled the diclofenac degradation rate, which can be attributed to the high catalytic effect, mediated via increased surface area and pore size of mineral surface in the low pH. Conversely, anatase, a crystal phase of titanium dioxide (TiO2), diminished the diclofenac degradation compared to treatments without TiO2. Hematite, on the other hand, showed no effect on diclofenac degradation. Photo-degradation products also varied with the mineral surface. We further assessed in vitro toxicological effects of photo-degraded products on two human cell lines, HEK293T and HepG2. Biological assays confirmed that photo-degraded compound 6 (1-(2,6-dichlorophenyl)indolin-2-one) decreased HEK293T cell survival significantly (p < 0.05) when compared to diclofenac in all concentrations. At lower concentrations, inhibition of HEK293T cells caused by compounds 4 (2-(8-chloro-9H-carbazol-1-yl)acetic acid), and 5 (2-(9H-carbazol-1-yl)acetic acid) was greater than diclofenac. Compound 7 (1-phenylindolin-2-one) was toxic only at 250 µM. Additionally, compound 6 decreased HepG2 cell viability significantly when compared to diclofenac. Overall, our data highlighted that mineralogy plays a vital role in environmental diclofenac transformation and its photo-degraded products. Some photo-degraded compounds can be more cytotoxic than the parent compound, diclofenac.

Cystargolide-based amide and ester Pz analogues as proteasome inhibitors and anti-cancer agents.

A series of cystargolide-based ß-lactone analogues containing nitrogen atoms at the Pz portion of the scaffold were prepared and evaluated as proteasome inhibitors, and for their cytotoxicity profile toward several cancer cell lines. Inclusion of one, two or even three nitrogen atoms at the Pz portion of the cystargolide scaffold is well tolerated, producing analogues with low nanomolar proteasome inhibition activity, in many cases superior to carfilzomib. Additionally, analogue 8g, containing an ester and pyrazine group at Pz, was shown to possess significant activity toward RPMI 8226 cells (IC50 = 21 nM) and to be less cytotoxic toward the normal tissue model MCF10A cells than carfilzomib.

Bannwarth's syndrome and a surgical dilemma: An uncommon zoonosis with a rare presentation.

Lyme's disease also known as Erythema chronicum Migrans, is a multisystem infectious disease caused by the spirochete "Borrelia burgdorferi" which is transmitted by "Ixodes" tick, with both specific and nonspecific manifestations. Nervous system involvement occurs in 10%-15% of untreated patients and typically involves lymphocytic meningitis, cranial neuritis, and/or polyradiculitis. Here, we are reporting an interesting and challenging case of Neuro-Borreliosis in a young officer cadet, meeting the description for Bannwarth's syndrome and presenting initially as a surgical emergency followed by paraparesis. The diagnosis was finally clinched based on clinical profile of Chronic Myeloradiculopathy with focal myositis in the setting of recent outdoor camping, and confirmed by demonstrating high IgG antibody titres in serum and Cerebro spinal fluid (CSF). The officer cadet was treated successfully with a 6 week course of Ceftriaxone and Doxycycline, and went back to full training.

DNA damage induced by KP372-1 hyperactivates PARP1 and enhances lethality of pancreatic cancer cells with PARP inhibition.

The overall prognosis for pancreatic cancer remains dismal and potent chemotherapeutic agents that selectively target this cancer are critically needed. Elevated expression of NAD(P)H:quinone oxidoreductase 1 (NQO1) is frequent in pancreatic cancer, and it offers promising tumor-selective targeting. Recently, KP372-1 was identified as a novel NQO1 redox cycling agent that induces cytotoxicity in cancer cells by creating redox imbalance; however, the mechanistic basis of KP372-1-induced cytotoxicity remains elusive. Here, we show that KP372-1 sensitizes NQO1-expressing pancreatic cancer cells and spares immortalized normal pancreatic duct cells, hTERT-HPNE. Notably, we found that KP372-1 is ~ 10- to 20-fold more potent than ß-lapachone, another NQO1 substrate, against pancreatic cancer cells. Mechanistically, our data strongly suggest that reactive oxygen species produced by NQO1-dependent redox cycling of KP372-1 cause robust DNA damage, including DNA breaks. Furthermore, we found that KP372-1-induced DNA damage hyperactivates the central DNA damage sensor protein poly(ADP-ribose) polymerase 1 (PARP1) and activates caspase-3 to initiate cell death. Our data also show that the combination of KP372-1 with PARP inhibition creates enhanced cytotoxicity in pancreatic cancer cells. Collectively, our study provides mechanistic insights into the cytotoxicity instigated by KP372-1 and lays an essential foundation to establish it as a promising chemotherapeutic agent against cancer.

XRN2 interactome reveals its synthetic lethal relationship with PARP1 inhibition.

Persistent R-loops (RNA-DNA hybrids with a displaced single-stranded DNA) create DNA damage and lead to genomic instability. The 5'-3'-exoribonuclease 2 (XRN2) degrades RNA to resolve R-loops and promotes transcription termination. Previously, XRN2 was implicated in DNA double strand break (DSB) repair and in resolving replication stress. Here, using tandem affinity purification-mass spectrometry, bioinformatics, and biochemical approaches, we found that XRN2 associates with proteins involved in DNA repair/replication (Ku70-Ku80, DNA-PKcs, PARP1, MCM2-7, PCNA, RPA1) and RNA metabolism (RNA helicases, PRP19, p54(nrb), splicing factors). Novel major pathways linked to XRN2 include cell cycle control of chromosomal replication and DSB repair by non-homologous end joining. Investigating the biological implications of these interactions led us to discover that XRN2 depletion compromised cell survival after additional knockdown of specific DNA repair proteins, including PARP1. XRN2-deficient cells also showed enhanced PARP1 activity. Consistent with concurrent depletion of XRN2 and PARP1 promoting cell death, XRN2-deficient fibroblast and lung cancer cells also demonstrated sensitivity to PARP1 inhibition. XRN2 alterations (mutations, copy number/expression changes) are frequent in cancers. Thus, PARP1 inhibition could target cancers exhibiting XRN2 functional loss. Collectively, our data suggest XRN2's association with novel protein partners and unravel synthetic lethality between XRN2 depletion and PARP1 inhibition.

A toxicological study on photo-degradation products of environmental ibuprofen: Ecological and human health implications.

Increasing quantities of pharmaceutical waste in the environment have disrupted the balance of ecosystems, and may have subsequent effects on human health. Although a handful of previous studies have shown the impacts of pharmaceutically active compounds on the environment, the toxicological effects of their degradation products remain largely unknown. In the current study, the photo-degradation products of environmental ibuprofen were assessed for both ecotoxicological and human health effects using a series of in vitro assays. Here, six of the major degradation products are synthesized with high purity (>98%) and characterized with 1HNMR, 13CNMR, FT-IR and HRMS. To evaluate human health effects, three gut microbiota species, Lactobacillus acidophilus, Enterococcus faecalis and Escherichia coli, and two human cell lines, HEK293T and HepG2, are exposed to various concentrations of ibuprofen and its degradation products. On L. acidophilus, the ibuprofen degradation product (±)-(2R,3R)-2-(4-isobutylphenyl)-5-methylhexan-3-ol shows a greater toxic effect while ibuprofen enhances its growth at lower concentrations. At higher concentrations, ibuprofen shows at least a 2-fold higher toxicity compared to that of its degradation products. However, E. faecalis shows little or no effect upon exposure to these compounds. An induction of the SOS response in E. coli is observed but limited to only ibuprofen and 4-acetylbenzoic acid. In human cell line studies, survival of both HEK293T and HepG2 cell lines is profoundly impaired by the photo-degradation products of (±)- (2R,3R)-2-(4-isobutylphenyl)-5-methylhexan-3-ol, (±)-(2R,3S)-2-(4-isobutylphenyl)-5-methylhexan-3-ol, and (±)-1-(4-(1-hydroxy-2methylpropyl)phenyl)ethan-1-one. In this work, the bioluminescence bacterium, Aliivibrio fischeri, is used as a model to assess environmental impact. Both ibuprofen and its degradation products inhibit the growth of this gram-negative bacteria with the primary compound showing the most significant impact. Overall, our results highlight that some of the degradation products of ibuprofen can be more toxic to human kidney cell line and liver cell line than the parent compound while ibuprofen can be more toxic to human gut microbiota and A. fischeri than ibuprofen degradation products.

How Much Bone Cement Is Utilized for Component Fixation in Primary Cemented Total Knee Arthroplasty?

BACKGROUND: No scientific evidence exists regarding the amount of bone cement used and discarded in primary cemented Total knee arthroplasty (TKA). The aim of this study was to identify the exact amount of bone cement utilized for component fixation in primary TKA. METHODS: In a prospective study carried out at five centers, 133 primary cemented TKAs were performed. One pack of 40g Palacos bone cement (PBC 40) was hand mixed and digitally applied during the surgery. After fixation of the TKA components, the remaining bone cement was methodically collected and weighed on a digital weighing scale. The actual quantity of cement utilized for component fixation was calculated. RESULTS: On an average, 22.1 g of bone cement was utilized per joint, which accounted to 39 % of 57 g, the solidified dry weight of PBC 40. Among 133 knees, the cement usage was 20 % to 50% in 109 knees, more than 50% in 20 knees and less than 20% in 4 knees. Knees which received larger sized femoral implant required more cement compared to medium and small sizes. Knees which had pulse lavage had more cement utilization compared to knees which had simple syringe lavage before implantation. CONCLUSION: Large quantity of bone cement was handled than actual requirements in primary TKA when a standard 40g pack was used with the digital application technique, resulting in sizeable discard of bone cement. Customizing cement pack according to the implant size can potentially avoid this cement wastage. Future research is required to study the utility and economic impact of smaller packs (20 g or 30 g) of bone cement in primary TKA.

Use of colchicine in pregnancy: a systematic review and meta-analysis.

OBJECTIVES: Colchicine is an anti-inflammatory agent used in the treatment of several rheumatological conditions. The use of colchicine in pregnancy is controversial. The current study aimed to systematically review and meta-analyse the existing data in the literature regarding the safety of colchicine in pregnancy. METHODS: A systematic review was carried out using six electronic databases, identifying all relevant studies where colchicine was administered to pregnant women, and where pregnancy-related outcomes were measured. The primary endpoints were miscarriage and major foetal malformation. Secondary endpoints included birthweight and gestational age at birth. RESULTS: Four studies were included for meta-analysis. Use of colchicine throughout pregnancy was not associated with an increased incidence of miscarriage or major foetal malformations. The incidence of miscarriage was significantly lower in women who took colchicine compared with those that did not. In women with FMF who took colchicine throughout the pregnancy, there was no significant difference in birthweight or gestational age compared with those who did not take colchicine. When not limited to FMF, colchicine use was associated with a significantly lower birthweight and gestational age compared with a control group including healthy women who did not take colchicine. CONCLUSIONS: Colchicine therapy did not significantly increase the incidence of foetal malformations or miscarriage when taken during pregnancy. Colchicine therapy for FMF should not be withheld on this basis during pregnancy.

The cohesin-like RecN protein stimulates RecA-mediated recombinational repair of DNA double-strand breaks.

RecN is a cohesin-like protein involved in DNA double-strand break repair in bacteria. The RecA recombinase functions to mediate repair via homologous DNA strand invasion to form D-loops. Here we provide evidence that the RecN protein stimulates the DNA strand invasion step of RecA-mediated recombinational DNA repair. The intermolecular DNA tethering activity of RecN protein described previously cannot fully explain this novel activity since stimulation of RecA function is species-specific and requires RecN ATP hydrolysis. Further, DNA-bound RecA protein increases the rate of ATP hydrolysis catalysed by RecN during the DNA pairing reaction. DNA-dependent RecN ATPase kinetics are affected by RecA protein in a manner suggesting a specific order of protein-DNA assembly, with RecN acting after RecA binds DNA. We present a model for RecN function that includes presynaptic stimulation of the bacterial repair pathway perhaps by contributing to the RecA homology search before ternary complex formation.

Leveraging an NQO1 Bioactivatable Drug for Tumor-Selective Use of Poly(ADP-ribose) Polymerase Inhibitors.

Therapeutic drugs that block DNA repair, including poly(ADP-ribose) polymerase (PARP) inhibitors, fail due to lack of tumor-selectivity. When PARP inhibitors and ß-lapachone are combined, synergistic antitumor activity results from sustained NAD(P)H levels that refuel NQO1-dependent futile redox drug recycling. Significant oxygen-consumption-rate/reactive oxygen species cause dramatic DNA lesion increases that are not repaired due to PARP inhibition. In NQO1+ cancers, such as non-small-cell lung, pancreatic, and breast cancers, cell death mechanism switches from PARP1 hyperactivation-mediated programmed necrosis with ß-lapachone monotherapy to synergistic tumor-selective, caspase-dependent apoptosis with PARP inhibitors and ß-lapachone. Synergistic antitumor efficacy and prolonged survival were noted in human orthotopic pancreatic and non-small-cell lung xenograft models, expanding use and efficacy of PARP inhibitors for human cancer therapy.

XRN2 Links Transcription Termination to DNA Damage and Replication Stress.

XRN2 is a 5'-3' exoribonuclease implicated in transcription termination. Here we demonstrate an unexpected role for XRN2 in the DNA damage response involving resolution of R-loop structures and prevention of DNA double-strand breaks (DSBs). We show that XRN2 undergoes DNA damage-inducible nuclear re-localization, co-localizing with 53BP1 and R loops, in a transcription and R-loop-dependent process. XRN2 loss leads to increased R loops, genomic instability, replication stress, DSBs and hypersensitivity of cells to various DNA damaging agents. We demonstrate that the DSBs that arise with XRN2 loss occur at transcriptional pause sites. XRN2-deficient cells also exhibited an R-loop- and transcription-dependent delay in DSB repair after ionizing radiation, suggesting a novel role for XRN2 in R-loop resolution, suppression of replication stress, and maintenance of genomic stability. Our study highlights the importance of regulating transcription-related activities as a critical component in maintaining genetic stability.

The Kub5-Hera/RPRD1B interactome: a novel role in preserving genetic stability by regulating DNA mismatch repair.

Ku70-binding protein 5 (Kub5)-Hera (K-H)/RPRD1B maintains genetic integrity by concomitantly minimizing persistent R-loops and promoting repair of DNA double strand breaks (DSBs). We used tandem affinity purification-mass spectrometry, co-immunoprecipitation and gel-filtration chromatography to define higher-order protein complexes containing K-H scaffolding protein to gain insight into its cellular functions. We confirmed known protein partners (Ku70, RNA Pol II, p15RS) and discovered several novel associated proteins that function in RNA metabolism (Topoisomerase 1 and RNA helicases), DNA repair/replication processes (PARP1, MSH2, Ku, DNA-PKcs, MCM proteins, PCNA and DNA Pol δ) and in protein metabolic processes, including translation. Notably, this approach directed us to investigate an unpredicted involvement of K-H in DNA mismatch repair (MMR) where K-H depletion led to concomitant MMR deficiency and compromised global microsatellite stability. Mechanistically, MMR deficiency in K-H-depleted cells was a consequence of reduced stability of the core MMR proteins (MLH1 and PMS2) caused by elevated basal caspase-dependent proteolysis. Pan-caspase inhibitor treatment restored MMR protein loss. These findings represent a novel mechanism to acquire MMR deficiency/microsatellite alterations. A significant proportion of colon, endometrial and ovarian cancers exhibit k-h expression/copy number loss and may have severe mutator phenotypes with enhanced malignancies that are currently overlooked based on sporadic MSI+ screening.

Pentalogy of Cantrell: a case report.

Pentalogy of Cantrell is a rare condition comprising anterior diaphragmatic defect, ventral abdominal wall defect, pericardial defect, intracardiac anomalies and lower sternal defect. Both sporadic and genetic causes are proposed. Prognosis depends on the severity of the defects and the associated cardiac anomalies. Two-dimensional sonography is sufficient for the diagnosis of this condition.

Kub5-Hera, the human Rtt103 homolog, plays dual functional roles in transcription termination and DNA repair.

Functions of Kub5-Hera (In Greek Mythology Hera controlled Artemis) (K-H), the human homolog of the yeast transcription termination factor Rtt103, remain undefined. Here, we show that K-H has functions in both transcription termination and DNA double-strand break (DSB) repair. K-H forms distinct protein complexes with factors that repair DSBs (e.g. Ku70, Ku86, Artemis) and terminate transcription (e.g. RNA polymerase II). K-H loss resulted in increased basal R-loop levels, DSBs, activated DNA-damage responses and enhanced genomic instability. Significantly lowered Artemis protein levels were detected in K-H knockdown cells, which were restored with specific K-H cDNA re-expression. K-H deficient cells were hypersensitive to cytotoxic agents that induce DSBs, unable to reseal complex DSB ends, and showed significantly delayed γ-H2AX and 53BP1 repair-related foci regression. Artemis re-expression in K-H-deficient cells restored DNA-repair function and resistance to DSB-inducing agents. However, R loops persisted consistent with dual roles of K-H in transcription termination and DSB repair.

Lateral Parapatellar Approach Without Tibial Tubercle Osteotomy for Fixed Valgus Deformity Correction in Total Knee Arthroplasty.

INTRODUCTION: The lateral parapatellar approach provides direct access to the pathological area in a valgus knee deformity and allows sequential titrated release of contracted lateral soft tissues during total knee arthroplasty. STEP 1 PREOPERATIVE PLANNING: Differentiate the flexible and fixed components of the valgus deformity by clinical and radiographic examination. STEP 2 EXPANSILE LATERAL ARTHROTOMY: Open the knee joint from the lateral side by coronal z-plasty of the lateral retinaculum, oblique lateral tenotomy of the quadriceps tendon, and iliotibial band release. STEP 3 QUADRICEPS SNIP AND JOINT EXPOSURE: Perform a quadriceps snip and expose the knee joint. STEP 4 TIBIAL AND DISTAL FEMORAL CUTS: Make proximal tibial and distal femoral cuts in appropriate alignment. STEP 5 EXTENSION GAP BALANCING: A rectangular extension gap is the goal. STEP 6 FLEXION GAP BALANCING: Determine the femoral component size and femoral rotation, and balance the flexion gap. STEP 7 COMPONENT FIXATION: Confirm tibial rotational alignment, fix the components, and assess patellar tracking. STEP 8 PROSTHETIC JOINT CLOSURE: Perform closure of the prosthetic joint with expanded lateral structures. RESULTS: Between 2003 and 2009, thirty-two knees with clinical valgus deformity of >10° underwent total knee arthroplasty with an expansile lateral arthrotomy technique11.IndicationsContraindicationsPitfalls & Challenges.

Efficacy and mid term results of lateral parapatellar approach without tibial tubercle osteotomy for primary total knee arthroplasty in fixed valgus knees.

The lateral parapatellar approach, despite providing direct access to the pathological area has not been widely accepted for knee arthroplasty in valgus deformities. We performed a modified lateral (Keblish) approach which consisted of coronal z plasty of lateral retinaculum, quadriceps snip, titrated sequential lateral release and closure with expanded lateral structures in 32 arthritic fixed valgus knees. In 30 knees, either tendon of popliteus or lateral collateral ligament or both could be preserved. At an average follow-up of 5 years, the valgus alignment improved from 25.4° (11°-60°) to 4° (0°-10°) and knee society score improved from 34 to 95 points. There was no late instability or revisions. This approach is rational, eliminates patella maltracking, is applicable in severe deformities and with titrated release, can preserve the posterolateral knee stabilizers that are necessary for long term implant survival.

Understanding the dose-response relationship of allopurinol: predicting the optimal dosage.

AIMS: The aim of the study was to identify and quantify factors that control the plasma concentrations of urate during allopurinol treatment and to predict optimal doses of allopurinol. METHODS: Plasma concentrations of urate and creatinine (112 samples, 46 patients) before and during treatment with various doses of allopurinol (50-600 mg daily) were monitored. Non-linear and multiple linear regression equations were used to examine the relationships between allopurinol dose (D), creatinine clearance (CLcr) and plasma concentrations of urate before (UP) and during treatment with allopurinol (UT). RESULTS: Plasma concentrations of urate achieved during allopurinol therapy were dependent on the daily dose of allopurinol and the plasma concentration of urate pre-treatment. The non-linear equation: UT = (1 - D/(ID50 + D)) × (UP - UR) + UR , fitted the data well (r(2) = 0.74, P < 0.0001). The parameters and their best fit values were: daily dose of allopurinol reducing the inhibitable plasma urate by 50% (ID50 = 226 mg, 95% CI 167, 303 mg), apparent resistant plasma urate (UR = 0.20 mmol l(-1), 95 % CI 0.14, 0.25 mmol l(-1)). Incorporation of CLcr did not significantly improve the fit (P = 0.09). CONCLUSIONS: A high baseline plasma urate concentration requires a high dose of allopurinol to reduce plasma urate below recommended concentrations. This dose is dependent on only the pre-treatment plasma urate concentration and is not influenced by CLcr .

Self-assembly of modified rhodamine-6G with tri-block copolymer: unusual vesicle formation, pH sensing and dye release properties.

A new rhodamine-6G derivative having a C18-alkyl chain self-assembles with an amphiphilic tri-block copolymer and forms stable vesicles in water or in water-ethanol (4 : 1, v/v) medium. The stability of the spirolactam form of the rhodamine-6G derivative in these vesicular structures, along with studies of controlled dye release and pH sensing are discussed. Transmission electron micrographs and DLS analyses confirm the formation of vesicular structures. Atomic force microscopy (AFM) images show that the self assembled tri-block copolymer-octadecyl rhodamine vesicles form near spherical nanostructures with a size ranging from 80 to 110 nm. Furthermore, the vesicular system is disassembled under acidic conditions, releasing the cargo which are an integral part of the vesicle. Dye-release studies showed that the release rates of the loaded dye in the vesicles could be well-controlled as a function of the media pH. These results offer an opportunity to use these nanovesicles as imaging reagents for probing media pH with their simultaneous use as nanocarriers for intracellular drug delivery.