1
|
Fellows T, Ho L, Flanagan S, Fogel R, Ojo D, Limson J. Gold nanoparticle-streptavidin conjugates for rapid and efficient screening of aptamer function in lateral flow sensors using novel CD4-binding aptamers identified through Crossover-SELEX. Analyst 2020; 145:5180-5193. [PMID: 32567629 DOI: 10.1039/d0an00634c] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
To decrease the burden of laborious and reagent-intensive screening of modified aptamers, their binding function requires assessment in assay formats compatible with the end diagnostic application. Here, we report on the use of an alternative and cost-effective approach: a rapid lateral flow assay (LFA) utilising streptavidin-conjugated gold nanoparticles (AuNP) as reporter molecules to screen novel ssDNA aptamers for their ability to detect CD4. Crossover-SELEX was employed to identify CD4-targeting aptamers from a ssDNA library enriched against a recombinant human CD4 protein (hCD4) conjugated to magnetic-beads and to endogenous CD4 expressed by U937 cells. Counter-selection with IgG-conjugated beads and CD4-negative Ramos RA-1 cells was employed. Following SELEX, four sequences (U4, U14, U20 and U26) were selected for candidate screening. Fluorescence confocal microscopy showed comparable localization of the Cy5-labeled aptamer U26, compared to antibodies binding CD4's cytoplasmic domain. Aptamer-hCD4 binding kinetics were evaluated by a qPCR-based magnetic-bead binding assay to unmodified aptamers. U26 exhibited the highest binding affinity (Kd = 2.93 ± 1.03 nM) to hCD4-conjugated beads. Citrate-stabilized gold nanoparticles (mean particle diameter, 10.59 ± 1.81 nm) were functionalized with streptavidin to allow immobilization of biotin-labeled aptamers. Except for U4, the aptamer-gold nanoparticle conjugates (Apt-AuNP) remained stable under physiological conditions with their size (approx. 15 nm) appropriate for use in the LFAs. Lateral-flow based screening was used to evaluate the suitability of the Apt-AuNPs as CD4-detecting reporter molecules by immobilizing hCD4 and flowing the nanoparticle conjugates across the LFA. Using this approach, two novel sequences were identified as being suitable for the detection of hCD4: visual detection at 9 min was obtained using U20 or U26. After 20 min, equivalent colorimetric hCD4 responses were observed between anti-CD4 monoclonal antibody (ΔI = 94.19 ± 3.71), an existing CD4 aptamer F1-62 (ΔI = 90.31 ± 19.31) and U26 (ΔI = 100.14 ± 14.61) LFA's, each demonstrating high specificity to hCD4 compared to IgG. From the above, Crossover-SELEX allowed for the successful identification of ssDNA aptamers able to detect hCD4. Streptavidin-conjugated AuNPs, when bound to candidate aptamers, show potential application here as screening tools for the rapid evaluation of aptamer performance in low-cost lateral flow diagnostics.
Collapse
Affiliation(s)
- Tamika Fellows
- Rhodes University Biotechnology Innovation Centre, Grahamstown, Eastern Cape, South Africa.
| | | | | | | | | | | |
Collapse
|
2
|
Akingbade O, Balogun S, Ojo D, Akinduti P, Okerentugba PO, Nwanze JC, Okonko IO. Resistant plasmid profile analysis of multidrug resistant Escherichia coli isolated from urinary tract infections in Abeokuta, Nigeria. Afr Health Sci 2014; 14:821-8. [PMID: 25834489 PMCID: PMC4370060 DOI: 10.4314/ahs.v14i4.8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Multi-drug resistant Escherichia coli has become a major threat and cause of many urinary tract infections (UTIs) in Abeokuta, Nigeria. OBJECTIVES This study was carried out to determine the resistant plasmids of multidrug resistant Escherichia coli isolated from (Urinary tract infections)UTIs in Abeokuta. METHODS A total of 120 Escherichia coli isolates were obtained from urine samples collected from patients attending inpatient and outpatient clinics presenting UTI; with their biodata. Antibiotics susceptibility was performed and multi-drug resistant isolates were selected for plasmid profiling. Plasmids were extracted by the alkaline lysis method, electrophoresed on 0.8% agarose gel and profiled using a gel-photo documentation system gel. RESULTS Escherichia coli isolates obtained shows high resistance to cloxacillin (92.5%), amoxicillin (90.8%), ampicillin (90.8%), erythromycin (75.8%), cotrimoxazole (70.0%), streptomycin (70.0%) and tetracycline (68.3%) while 85.8% and 84.2% were susceptible to gentamycin and ceftazidime respectively. Sixteen Escherichia coli strains were observed to be resistant to more than two classes of antibiotics. The resistant plasmid DNA was detectable in 6(37.5%) of the 16 multidrug resistant Escherichia coli having single sized plasmids of the same weight 854bp and were all resistant to erythromycin, cefuroxime, cloxacillin, amoxicillin, ampicillin and cotrimoxazole. CONCLUSION This study has highlighted the emergence of multidrug resistant R-plasmids among Escherichia coli causing urinary tract infections in Abeokuta, Nigeria. There is a high level of resistance to many antimicrobials that are frequently used in Abeokuta, Nigeria.
Collapse
Affiliation(s)
- O Akingbade
- Department of Microbiology, Federal University of Agriculture, Abeokuta, Nigeria
| | - S Balogun
- Department of Microbiology, Federal University of Agriculture, Abeokuta, Nigeria
| | - D Ojo
- Department of Microbiology, Federal University of Agriculture, Abeokuta, Nigeria
| | - P Akinduti
- Department of Medical Microbiology & Parasitology, Olabisi Onabanjo University, Ago-Iwoye, Nigeria
| | - P O Okerentugba
- Medical Microbiology Unit, Department of Microbiology, University of Port Harcourt, East- West Road, P.M.B. 5323, Choba, Port Harcourt, Rivers State, Nigeria
| | - J C Nwanze
- Department of Pharmacology and Therapeutics, Igbinedion University, Okada, Edo State, Nigeria
| | - I O Okonko
- Medical Microbiology Unit, Department of Microbiology, University of Port Harcourt, East- West Road, P.M.B. 5323, Choba, Port Harcourt, Rivers State, Nigeria
| |
Collapse
|
3
|
Wei F, Ojo D, Lin X, Wong N, He L, Yan J, Xu S, Major P, Tang D. BMI1 attenuates etoposide-induced G2/M checkpoints via reducing ATM activation. Oncogene 2014; 34:3063-75. [PMID: 25088203 DOI: 10.1038/onc.2014.235] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Revised: 06/11/2014] [Accepted: 06/20/2014] [Indexed: 12/17/2022]
Abstract
The BMI1 protein contributes to stem cell pluripotency and oncogenesis via multiple functions, including its newly identified role in DNA damage response (DDR). Although evidence clearly demonstrates that BMI1 facilitates the repair of double-stranded breaks via homologous recombination (HR), it remains unclear how BMI1 regulates checkpoint activation during DDR. We report here that BMI1 has a role in G2/M checkpoint activation in response to etoposide (ETOP) treatment. Ectopic expression of BMI1 in MCF7 breast cancer and DU145 prostate cancer cells significantly reduced ETOP-induced G2/M arrest. Conversely, knockdown of BMI1 in both lines enhanced the arrest. Consistent with ETOP-induced activation of the G2/M checkpoints via the ATM pathway, overexpression and knockdown of BMI1, respectively, reduced and enhanced ETOP-induced phosphorylation of ATM at serine 1981 (ATM pS1981). Furthermore, the phosphorylation of ATM targets, including γH2AX, threonine 68 (T68) on CHK2 (CHK2 pT68) and serine 15 (S15) on p53 were decreased in overexpression and increased in knockdown BMI1 cells in response to ETOP. In line with the requirement of NBS1 in ATM activation, we were able to show that BMI1 associates with NBS1 and that this interaction altered the binding of NBS1 with ATM. BMI1 consists of a ring finger (RF), helix-turn-helix-turn-helix-turn (HT), proline/serine (PS) domain and two nuclear localization signals (NLS). Although deletion of either RF or HT did not affect the association of BMI1 with NBS1, the individual deletions of PS and one NLS (KRMK) robustly reduced the interaction. Stable expression of these BMI1 mutants decreased ETOP-induced ATM pS1981 and CHK2 pT68, but not ETOP-elicited γH2AX in MCF7 cells. Furthermore, ectopic expression of BMI1 in non-transformed breast epithelial MCF10A cells also compromised ETOP-initiated ATM pS1981 and γH2AX. Taken together, we provide compelling evidence that BMI1 decreases ETOP-induced G2/M checkpoint activation via reducing NBS1-mediated ATM activation.
Collapse
Affiliation(s)
- F Wei
- 1] Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Ontario, Canada [2] Father Sean O'Sullivan Research Institute, Hamilton, Ontario, Canada [3] The Hamilton Center for Kidney Research, St. Joseph's Hospital, Hamilton, Ontario, Canada [4] The Genetics Laboratory, Institute of Women and Children's Health, Longgang District, Shenzhen, Guangdong, P.R. China
| | - D Ojo
- 1] Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Ontario, Canada [2] Father Sean O'Sullivan Research Institute, Hamilton, Ontario, Canada [3] The Hamilton Center for Kidney Research, St. Joseph's Hospital, Hamilton, Ontario, Canada
| | - X Lin
- 1] Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Ontario, Canada [2] Father Sean O'Sullivan Research Institute, Hamilton, Ontario, Canada [3] The Hamilton Center for Kidney Research, St. Joseph's Hospital, Hamilton, Ontario, Canada
| | - N Wong
- 1] Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Ontario, Canada [2] Father Sean O'Sullivan Research Institute, Hamilton, Ontario, Canada [3] The Hamilton Center for Kidney Research, St. Joseph's Hospital, Hamilton, Ontario, Canada
| | - L He
- 1] Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Ontario, Canada [2] Father Sean O'Sullivan Research Institute, Hamilton, Ontario, Canada [3] The Hamilton Center for Kidney Research, St. Joseph's Hospital, Hamilton, Ontario, Canada [4] Massachusetts General Hospital (MGH), Harvard Medical School, Boston, MA, USA
| | - J Yan
- 1] Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Ontario, Canada [2] Father Sean O'Sullivan Research Institute, Hamilton, Ontario, Canada [3] The Hamilton Center for Kidney Research, St. Joseph's Hospital, Hamilton, Ontario, Canada
| | - S Xu
- 1] Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Ontario, Canada [2] Father Sean O'Sullivan Research Institute, Hamilton, Ontario, Canada [3] The Hamilton Center for Kidney Research, St. Joseph's Hospital, Hamilton, Ontario, Canada
| | - P Major
- Department of Oncology, McMaster University, Hamilton, Ontario, Canada
| | - D Tang
- 1] Division of Nephrology, Department of Medicine, McMaster University, Hamilton, Ontario, Canada [2] Father Sean O'Sullivan Research Institute, Hamilton, Ontario, Canada [3] The Hamilton Center for Kidney Research, St. Joseph's Hospital, Hamilton, Ontario, Canada
| |
Collapse
|