A low-cost paper-based aptasensor for simultaneous trace-level monitoring of mercury (II) and silver (I) ions.

Mercury (Hg2+) and silver (Ag+) ions possess the harmful effects on public health and environment that makes it essential to develop the sensing techniques with great sensitivity for the ions. Metal ions commonly coexist in the different biological and environmental systems. Hence, it is an urgent demand to design a simple method for the simultaneous detection of metal ions, peculiarly in the case of coexisting Hg2+ and Ag+. This study introduces a low-cost paper-based aptasensor to monitor Hg2+ and Ag+, simultaneously. The strategy of the sensing array is according to the conformational changes of Hg2+- and Ag+-specific aptamers and their release from the GO surface after the injection of the target sample on the sensing platform. Through monitoring the fluorescence recovery changes against the concentrations of the ions, Hg2+ and Ag+ can be determined as low as 1.33 and 1.01 pM. The paper-based aptasensor can simultaneously detect the ions within about 10 min. The aptasensor is applied prosperously to monitor Hg2+ and Ag+ in human serum, water, and milk. The designed aptasensor with the main advantages of simplicity and feasibility holds the supreme potential to develop a cost-effective sensing method for environmental monitoring, food control, and human diagnostics.

Managed care opportunities and approaches to supporting appropriate selection of treatment for sight preservation.

When evaluating the impact of vision-destroying diseases, pharmacologic therapies represent a significant cost to patients, insurance providers, and society. Currently, up to 11 million people in the United States have some form of age-related macular degeneration (AMD), which is one of the leading causes of vision loss in older Americans. Ophthalmologists have administered more than 6 million intravitreal injections of aflibercept, bevacizumab, pegaptanib, and ranibizumab last year. Comprehensive assessment requires managed care administrators and clinicians to understand the direct and indirect costs of vision loss as well as the comparative safety and efficacy profiles for each agent. In AMD, it is critical to understand the established and emerging treatment patterns.

Molecular Selection, Modification and Development of Therapeutic Oligonucleotide Aptamers.

Monoclonal antibodies are the dominant agents used in inhibition of biological target molecules for disease therapeutics, but there are concerns of immunogenicity, production, cost and stability. Oligonucleotide aptamers have comparable affinity and specificity to targets with monoclonal antibodies whilst they have minimal immunogenicity, high production, low cost and high stability, thus are promising inhibitors to rival antibodies for disease therapy. In this review, we will compare the detailed advantages and disadvantages of antibodies and aptamers in therapeutic applications and summarize recent progress in aptamer selection and modification approaches. We will present therapeutic oligonucleotide aptamers in preclinical studies for skeletal diseases and further discuss oligonucleotide aptamers in different stages of clinical evaluation for various disease therapies including macular degeneration, cancer, inflammation and coagulation to highlight the bright commercial future and potential challenges of therapeutic oligonucleotide aptamers.

Nucleic acid aptamers for capture and detection of Listeria spp.

The purpose of this study was to identify biotinylated single-stranded (ss) DNA aptamers with binding specificity to Listeria and use these for capture and subsequent qPCR detection of the organism. For aptamer selection, SELEX (systematic evolution of ligands by exponential enrichment) was applied to a biotin-labeled ssDNA combinatorial library. After multiple rounds of selection and counter-selection, aptamers separated, sequenced, and characterized by flow cytometry showed binding affinities to L. monocytogenes of 18-23%. Although selected for using L. monocytogenes, these aptamers showed similar binding affinity for other members of the Listeria genus and low binding affinity for non-Listeria species. One aptamer, Lbi-17, was chosen for development of a prototype capture and detection assay. When Lbi-17 was conjugated to magnetic beads and used in a combined aptamer magnetic capture (AMC)-qPCR assay, the pathogen could be detected at concentrations <60 CFU/500 µl buffer in the presence of a heterogeneous cocktail of non-Listeria bacterial cells, with a capture efficiency of 26-77%. Parallel experiments using immunomagnetic separation (IMS)-qPCR produced the same detection limit but lower capture efficiency (16-21%). Increasing assay volume to 10 and 50 ml resulted in reduced capture efficiency and higher limits of detection, at 2.7 and 4.8 log10 CFU L. monocytogenes per sample, respectively, for the AMC-qPCR assay. Biotinylated ssDNA aptamers are promising ligands for food-borne pathogen concentration prior to detection using molecular methods.

Cost and effectiveness of therapy for wet age-related macular degeneration in routine clinical practice.

PURPOSE: Evaluation of the cost and effectiveness of therapy for patients with the wet form of age-related macular degeneration (AMD) in routine clinical practice. METHODS: A retrospective multicentre evaluation of changes in the best-corrected visual acuity in applied kinds of therapy and a comparison with the cost of individual therapeutic procedures. RESULTS: An overall total of 788 eyes of 763 patients with an average age of 73.2 ± 8.6 years was evaluated for a 1-year minimum period. In the ranibizumab and pegaptanib therapy groups, a reduction of 1.3 letters (p = 0.303) and 1.4 letters (p = 0.197) was found, respectively. In the group of photodynamic therapy (PDT) with verteporfin, a reduction of 5.2 letters was achieved (p < 0.001). Under the conditions of routine practice in the Czech Republic, the annual cost is highest (EUR 5,467.63/patient) in patients with pegaptanib therapy. The annual cost in patients with ranibizumab therapy is lower by EUR 1,220.16. The cost is nearly half (EUR 2,783.65) in the group treated with PDT with verteporfin. CONCLUSION: An initiation of AMD therapy by ranibizumab is cost-effective as compared to pegaptanib. Both ranibizumab and pegaptanib are significantly more efficient as compared to PDT with verteporfin. Therapy with ranibizumab and pegaptanib, as compared to PDT with verteporfin, prevents the loss of 1 line of vision on the ETDRS chart for EUR 1,225.98 and 2,286.18, respectively.

Highly parallel single-molecule amplification approach based on agarose droplet polymerase chain reaction for efficient and cost-effective aptamer selection.

We have developed a novel method for efficiently screening affinity ligands (aptamers) from a complex single-stranded DNA (ssDNA) library by employing single-molecule emulsion polymerase chain reaction (PCR) based on the agarose droplet microfluidic technology. In a typical systematic evolution of ligands by exponential enrichment (SELEX) process, the enriched library is sequenced first, and tens to hundreds of aptamer candidates are analyzed via a bioinformatic approach. Possible candidates are then chemically synthesized, and their binding affinities are measured individually. Such a process is time-consuming, labor-intensive, inefficient, and expensive. To address these problems, we have developed a highly efficient single-molecule approach for aptamer screening using our agarose droplet microfluidic technology. Statistically diluted ssDNA of the pre-enriched library evolved through conventional SELEX against cancer biomarker Shp2 protein was encapsulated into individual uniform agarose droplets for droplet PCR to generate clonal agarose beads. The binding capacity of amplified ssDNA from each clonal bead was then screened via high-throughput fluorescence cytometry. DNA clones with high binding capacity and low K(d) were chosen as the aptamer and can be directly used for downstream biomedical applications. We have identified an ssDNA aptamer that selectively recognizes Shp2 with a K(d) of 24.9 nM. Compared to a conventional sequencing-chemical synthesis-screening work flow, our approach avoids large-scale DNA sequencing and expensive, time-consuming DNA synthesis of large populations of DNA candidates. The agarose droplet microfluidic approach is thus highly efficient and cost-effective for molecular evolution approaches and will find wide application in molecular evolution technologies, including mRNA display, phage display, and so on.

[Cost-effectiveness of ranibizumab, photodynamic therapy and pegaptanib sodium in the treatment of neovascular age-related macular degeneration in Japanese].

PURPOSE: To perform cost-utility analysis of ranibizumab, photodynamic therapy (PDT) and pegaptanib sodium treatment of neovascular age-related macular degeneration (AMD) with subfoveal choroidal neovascularization. MATERIALS AND METHODS: The analyses were performed on a 75-year old man with the starting visual acuity of letter score of 50 on an Early Treatment of Diabetic Retinopathy Study (ETDRS) chart, with the affected eye having better sight than the contralateral eye, for the time horizons of 1 and 11 year (s). Visual acuity data from the large controlled studies for ranibizumab, photodynamic therapy and pegaptanib sodium, were applied. The results were compared with best supportive care (BSC) data. Cost indications included direct medical costs and costs related with social blindness. Utility values were estimated from the time trade off method. This analysis was performed from a societal perspective. RESULTS: In the 1-year model, cost of treatment was dominant in the treatment groups, whereas the cost of blindness was dominant in the BSC. In the 11-year model, influence of cost of blindness resulted in the increasing costs for BSC. Of note, ranibizumab and PDT were less costly and showed an increase in utility compared to the BSC. Pegaptanib sodium was found to be costly. Sensitivity analysis found that the results were robust to changes in various model parameters. CONCLUSION: In the current model, ranibizumab and PDT confer quality-adjusted life years (QALY) gains and are less costly compared to BSC in the lifetime treatment. In contrast, pegaptanib sodium treatment could be considered to be of minimal cost-effectiveness. Ranibizumab and PDT confer excellent value in the models of the lifetime treatment.

[Differences in the treatment of exudative age-related macular degeneration in Germany and Great Britain]. / Unterschiede in der Therapie der exsudativen altersabhängigen Makuladegeneration in Deutschland und Großbritannien.

The treatment of age-related macular degeneration with anti-VEGF medications has resulted not only in significant improvements in eye treatment but also in rising costs of ophthalmological therapy. This new treatment has been rapidly introduced into daily practice in Germany with its social security healthcare system and also in Great Britain with its National Health Service. In both countries the most prevalent treatment scheme currently includes three baseline injections of ranibizumab followed by additional injections depending on persisting disease activity.

Advances in aptamers.

Aptamers are nucleic acid sequences synthesized through in vitro selection and amplification technique, possessing a broader range of applications in therapeutics, biosensing, diagnostics, and research. Aptamers offer a number of advantages over their antibodies counterpart, one of them is their ability to undergo chemical derivatization to increase their life in the body fluids and bioavailability in animals. Although aptamers were discovered in 1990s, they have become one of the most widely investigated molecules, with a huge number of publications in the last decade. This article presents an overview of the advancements that have been made in aptamers. We mainly focused on articles published since 2005.

A cost-effectiveness analysis of three treatments for age-related macular degeneration.

PURPOSE: The purpose of this study was to evaluate the cost effectiveness of pegaptanib sodium and ranibizumab injections compared with photodynamic therapy (PDT) with verteporfin for the treatment of choroidal neovascularization secondary to age-related macular degeneration. METHODS: The analyses were performed using outcomes data from the pivotal trials for each treatment and the medicare reimbursable costs for each treatment and associated medical procedures. A multistate transition model with 3-month cycles was created to compare incremental medical costs associated with pegaptanib or ranibizumab versus PDT for patients with starting vision of 20/40, 20/80, and 20/200 Snellen equivalent. RESULTS: Two-year medical treatment costs ranged from $3,100 to $54,100 depending on treatment and lesion type. Photodynamic therapy was less costly and more effective than pegaptanib for predominantly classic and minimally classic lesions. Ranibizumab was not only more effective but also more costly than PDT for all lesion types. CONCLUSION: Compared with PDT, pegaptanib is inferior in both cost and effectiveness, whereas ranibizumab has a greater effectiveness. Because ranibizumab does not meet 1 of the common thresholds for being considered cost effective (<$50,000 per quality-adjusted life year), there is rationale to seek other therapies that are more cost effective.

Cost-effectiveness of ranibizumab compared with pegaptanib in neovascular age-related macular degeneration.

OBJECTIVE: To assess the cost-effectiveness of ranibizumab compared with pegaptanib in the treatment of patients with minimally classic/occult neovascular age-related macular degeneration (AMD), from a societal perspective in Spain. METHODS: We constructed a Markov model with five states defined by visual acuity (VA) in the better-seeing eye (Snellen scale): VA >20/40, < or =20/40 to >20/80, < or =20/80 to >20/200, < or =20/200 to >20/400, < or =20/400, and an additional death state. Two cohorts of patients were distributed along the VA states, and treated with either ranibizumab or pegaptanib. Transition probabilities assigned for movement between these states with both drugs were obtained from published randomized clinical trials. Medical costs related to AMD treatment and follow-up, medical costs related to AMD comorbidities, and non-medical-related costs were taken into account. Costs (2008 Euro), health outcomes (Quality-adjusted life years--QALYs), both discounted at a 3.5% annual rate, and incremental cost-effectiveness ratios (ICER: euro/QALY), were determined for a lifetime horizon in the base case analysis. Sensitivity analyses were conducted to explore different scenarios and assumptions in the model. RESULTS: Treating patients with varying degrees of visual impairment with monthly ranibizumab instead of pegaptanib was 71,206 euro more costly and provided 2.437 additional QALYs (29,224 euro/QALY). When administered on an as-needed basis, as in the Prospective Optical Coherence Tomography Imaging of Patients with Neovascular AMD Treated with Intraocular Ranibizumab (PrONTO) trial, the cost per QALY gained with ranibizumab was reduced to 4,623 euro. CONCLUSIONS: The cost per QALY gained with monthly ranibizumab compared with pegaptanib in the minimally classic/occult neovascular AMD population is just below the 30,000 euro threshold below which new drugs are sometimes regarded as cost-effective strategies in Spain. In this model, the key variables with greater impact on the cost-effectiveness results were the selected time horizon and the chosen extrapolation method, the source for data on pegaptanib efficacy and the number of ranibizumab injections. When administered on an as-needed basis, ranibizumab was a cost-effective strategy compared to pegaptanib in this population.

Ranibizumab and pegaptanib for the treatment of age-related macular degeneration: a systematic review and economic evaluation.

OBJECTIVES: To assess the clinical effectiveness and cost-effectiveness of ranibizumab and pegaptanib for subfoveal choroidal neovascularisation (CNV) associated with wet age-related macular degeneration (AMD). DATA SOURCES: Electronic databases were searched from inception to September 2006. Experts in the field were consulted and manufacturers' submissions were examined. REVIEW METHODS: The quality of included studies was assessed using standard methods and the clinical effectiveness data were synthesised through a narrative review with full tabulation of results. A model was developed to estimate the cost-effectiveness of ranibizumab and of pegaptanib (separately), compared with current practice or best supportive care, from the perspective of the NHS and Personal Social Services. Two time horizons were adopted for each model. The first adopted time horizons determined by the available trial data. The second analysis extrapolated effects of treatment beyond the clinical trials, adopting a time horizon of 10 years. RESULTS: The combined analysis of two randomised controlled trials (RCTs) of pegaptanib [0.3 mg (licensed dose), 1.0 mg and 3.0 mg] versus sham injection in patients with all lesion types was reported by three publications (the VISION study). Three published RCTs of ranibizumab were identified (MARINA, ANCHOR, FOCUS), and an additional unpublished RCT was provided by the manufacturer (PIER). Significantly more patients lost less than 15 letters of visual acuity at 12 months when taking pegaptanib (0.3 mg: 70% of patients; 1.0 mg: 71% of patients; 3.0 mg: 65% of patients) or ranibizumab (0.3 mg: 94.3-94.5%; 0.5 mg: 94.6-96.4%) than sham injection patients (55% versus pegaptanib and 62.2% versus ranibizumab) or, in the case of ranibizumab, photodynamic therapy (PDT) (64.3%). The proportion of patients gaining 15 letters or more (a clinically important outcome having a significant impact on quality of life) was statistically significantly greater in the pegaptanib group for doses of 0.3 and 1.0 mg but not for 3.0 mg, and for all ranibizumab groups compared to the sham injection groups or PDT. This was also statistically significant for patients receiving 0.5 mg ranibizumab plus PDT compared with PDT plus sham injection. Pegaptanib patients lost statistically significantly fewer letters after 12 months of treatment than the sham group [mean letters lost: 7.5 (0.3 mg), 6.5 (1.0 mg) or 10 (3.0 mg) vs 14.5 (sham)]. In the MARINA and ANCHOR trials, ranibizumab patients gained letters of visual acuity at 12 months whereas patients with sham injection or PDT lost about 10 letters (p<0.001) and in the PIER study, ranibizumab patients lost significantly fewer than the sham injection group. Significantly fewer patients receiving pegaptanib or ranibizumab deteriorated to legal blindness compared with the control groups. Adverse events were common for both pegaptanib andranibizumab but most were mild to moderate. Drug costs for 1 year of treatment were estimated as 4626 pounds for pegaptanib and 9134 pounds for ranibizumab. Non-drug costs accounted for an additional 2614 pounds for pegaptanib and 3120 pounds for ranibizumab. Further costs are associated with the management of injection-related adverse events, from 1200 pounds to 2100 pounds. For pegaptanib compared with usual care, the incremental cost-effectiveness ratio (ICER) ranged from 163,603 pounds for the 2-year model to 30,986 pounds for the 10-year model. Similarly, the ICERs for ranibizumab for patients with minimally classic and occult no classic lesions, compared with usual care, ranged from 152,464 pounds for the 2-year model to 25,098 pounds for the 10-year model. CONCLUSIONS: Patients with AMD of any lesion type benefit from treatment with pegaptanib or ranibizumab on measures of visual acuity when compared with sham injection and/or PDT. Patients who continued treatment with either drug appeared to maintain benefits after 2 years of follow-up. When comparing pegaptanib and ranibizumab, the evidence was less clear due to the lack of direct comparison through head-to-head trials and the lack of opportunity for indirect statistical comparison due to heterogeneity. The cost-effectiveness analysis showed that the two drugs offered additional benefit over the comparators of usual care and PDT but at increased cost. Future research should encompass trials to compare pegaptanib with ranibizumab and bevacizumab, and to investigate the role of verteporfin PDT in combination with these drugs. Studies are also needed to assess adverse events outside the proposed RCTs, to consider the optimal dosing regimes of these drugs and the benefits of re-treatment after initial treatment, and to review costing in more detail. Health state utilities and their relationship with visual acuity and contrast sensitivity, the relationship between duration of vision loss and the quality of life and functional impact of vision loss, behavioural studies of those genetically at risk are other topics requiring further research.

Cost-effectiveness model for neovascular age-related macular degeneration: comparing early and late treatment with pegaptanib sodium based on visual acuity.

OBJECTIVE: To compare the cost-effectiveness of pegaptanib and usual care within three distinct cohorts of subfoveal neovascular age-related macular degeneration (NV-AMD) patients, that is, those with early, moderate, and late disease, using a comprehensive economic model. METHODS: A Markov framework was used to model lifetime movement of a subfoveal NV-AMD cohort through health states based on visual acuity. The model takes a US payer perspective of patients over the age of 65 years. Clinical efficacy was based on published results for the 0.3 mg pegaptanib and usual care groups. Expert interviews were conducted to determine adverse event treatment patterns and vision rehabilitation resource use. Incidence and costs of comorbidities such as depression and fractures associated with the effects of declining visual acuity were based on our previously published analysis of Medicare data. Transition probabilities were derived from published clinical trial data for each 3-month cycle. Utilities were derived from published sources. Three runs of the model were conducted with cohorts of newly diagnosed patients. Patients were classified as having early, moderate, or late NV-AMD defined as visual acuity in the better-seeing eye of 20/40 to more than 20/80, 20/80 to more than 20/200, and 20/200 to more than 20/400, respectively. Costs and outcomes were discounted 3.0% per annum. RESULTS: Incremental costs per vision-year gained and per quality-adjusted life-year (QALY) gained for early NV-AMD patients were approximately one-third those of patients with late disease ($15,279 vs. $57,230 and $36,282 vs. $132,381, respectively). On average, patients treated early with either pegaptanib or usual care incurred lower lifetime total direct costs than those treated later. Sensitivity analysis showed that base-case incremental costs per QALY gained for pegaptanib versus usual care were relatively robust. CONCLUSIONS: For patients with subfoveal NV-AMD, treatment with pegaptanib should be started as early as possible to maximize the clinical and economic benefits.

Cost-effectiveness of ranibizumab compared with photodynamic treatment of neovascular age-related macular degeneration.

OBJECTIVE: This study compared the cost-effectiveness of ranibizumab with that of photodynamic therapy (PDT) in the treatment of predominantly classic choroidal neovascularization secondary to age-related macular degeneration (AMD) from the perspective of a third-party payer in a Spanish setting. METHODS: We constructed a Markov model with 5 states defined by visual acuity (VA) in the better-seeing eye (Snellen scale), as follows: VA >20/40, 20/80, 20/200, 20/400, and

Cost-effectiveness of pegaptanib compared to photodynamic therapy with verteporfin and to standard care in the treatment of subfoveal wet age-related macular degeneration in Canada.

BACKGROUND: Age-related macular degeneration (AMD) is characterized by loss of central vision and is the leading cause of blindness among persons over the age of 50 years in Canada. The wet form of AMD has 3 subtypes-occult, minimally classic, and predominantly classic. Photodynamic therapy (PDT) with verteporfin is indicated only for the category of predominantly classic wet AMD. Currently, there are no treatments available for the other AMD subtypes. Pegaptanib sodium was the first pharmacologic therapy approved in Canada for the treatment of subfoveal wet AMD regardless of subtype. OBJECTIVE: The aim of this study was to examine the cost-effectiveness of pegaptanib versus PDT with verteporfin and versus standard care for the treatment of subfoveal wet AMD in patients aged 65 years in Canada. METHODS: A Markov model based on visual acuity in the better-seeing eye was developed. Clinical efficacy was taken from the clinical trials. Costs of treatment, comorbidities (eg, depression, fractures, need for assisted living), vision rehabilitation, visual aids, and adverse events were considered. Costs, utilities, and mortality were estimated from data from the available published literature. Costs were reported in 2004 Canadian dollars, and costs and outcomes were discounted at 3% per annum. Lifetime costs, quality-adjusted life-years (QALYs), and vision years gained (VYGs) were estimated. Sensitivity analyses were performed to determine model robustness. RESULTS: Patients who received pegaptanib experienced more QALYs gained (4.17) and VYGs (3.83) compared with patients who received PDT (3.87 and 3.01, respectively) or standard care (3.96 and 3.26). Mean total costs per patient were greater in patients who received pegaptanib compared to those who received PDT or standard care ($20,016 vs $15,345 or $7669, respectively). The incremental cost per QALY in patients receiving pegaptanib compared to those receiving PDT was $49,052 and $59,039 for patients receiving pegaptanib versus standard care. The incremental cost per VYG was $20,401 and $21,559 with pegaptanib versus PDT and standard care, respectively. Sensitivity analyses found that the model was relatively robust to changes in various model parameters. CONCLUSION: The results of this analysis suggest that in Canada, pegaptanib is a cost-effective treatment for subfoveal wet AMD in elderly patients, regardless of lesion subtype, compared to PDT with verteporfin and to standard care.