Facile Construction of i-Motif DNA-Conjugated Gold Nanostars as Near-Infrared and pH Dual-Responsive Targeted Drug Delivery Systems for Combined Cancer Therapy.

Stimuli-responsive DNA-based nanostructures have emerged as promising vehicles for intelligent drug delivery. In this study, i-motif DNA-conjugated gold nanostars (GNSs) were fabricated in a facile manner as stimuli-responsive drug delivery systems (denoted as A-GNS/DNA/DOX) for the treatment of cancer via combined chemo-photothermal therapy. The i-motif DNA is sensitive to the environmental pH and can switch from a single-stranded structure to a C-tetrad (i-motif) structure as the environmental pH decreases from neutral (∼7.4) to acidic (<6.0). The loaded drug can then be released along with the conformational changes. To enhance cellular uptake and improve cancer cell selectivity, the aptamer AS1411, which recognizes nucleolins, was employed as a targeting moiety. The A-GNS/DNA/DOX nanocomposites were found to be highly capable of photothermal conversion and exhibited photostability under near-infrared (NIR) irradiation, and the pH and NIR irradiation effectively triggered the drug-release behaviors. In addition, the A-GNS/DNA/DOX nanocomposites exhibited good biocompatibility. The targeting recognition enabled the A-GNS/DNA/DOX to exhibit higher cellular uptake and therapeutic efficiency than the GNS/DNA/DOX. Notably, under NIR irradiation, a synergistic effect between chemotherapy and photothermal therapy can be achieved with the proposed delivery system, which exhibits much higher therapeutic efficiency both in monolayer cancer cells and tumor spheroids as compared with a single therapeutic method. This study highlights the potential of GNS/DNA nanoassemblies for intelligent anticancer drug delivery and combined cancer therapy.

First Evidence of the Liposome-Mediated Deintercalation of Anticancer Drug Doxorubicin from the Drug-DNA Complex: A Spectroscopic Approach.

Biocompatible liposomes were used for the first time to study the deintercalation process of a prominent anticancer drug, doxorubicin (DOX), from doxorubicin-intercalated DNA (DOX-DNA complex) under controlled experimental conditions. The study revealed that anionic liposomes (DMPG liposomes) appeared to be the most effective to bring in the highest percentage of drug release while cationic liposomes (DOTAP liposomes) scored the lowest percentage of release. The drug release was primarily attributed to the electrostatic interaction between liposomes and drug molecules. Apart from this interaction, changes in the hydrophobicity of the medium upon addition of liposomes to the DNA-drug solution accompanied by lipoplex formation between DNA and liposomes were also attributed to the observed deintercalation. The CD and the time-resolved rotational relaxation studies confirmed that lipoplex formation took place between liposomes and DNA owing to electrostatic interaction. The confocal study revealed that in the postrelease period, DOX binds with liposomes. The reason behind the binding is electrostatic interaction as well as the unique bilayer structure of liposomes which helps it to act as a "hydrophobic sink" for DOX. The study overall highlighted a novel strategy for deintercalation of drug using biocompatible liposomes, as the release of the drug can be controlled over a period of time by varying the concentration and composition of the liposomes.

Lipoplex-Mediated Deintercalation of Doxorubicin from Calf Thymus DNA-Doxorubicin Complex.

In this paper, we report the lipoplex-mediated deintercalation of anticancer drug doxorubicin (DOX) from the DOX-DNA complex under controlled experimental conditions. We used three zwitterionic liposomes, namely, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), and 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine (POPC), which are widely different in their phase transition temperatures to form a lipoplex with calf thymus DNA in the presence of Ca(2+) ions. The study revealed that DPPC being in sol-gel phase was more effective in releasing the drug from the DOX-DNA complex compared with liposomes that remain in liquid crystalline phase (DMPC and POPC). The higher extent of drug release in the case of DPPC liposomes was attributed to the stronger lipoplex formation with DNA as compared with that of other liposomes. Owing to the relatively smaller head group area, the DPPC liposomes in their sol-gel phase can absorb a larger number of Ca(2+) ions and hence offer a strong electrostatic interaction with DNA. This interaction was confirmed by time-resolved anisotropy and circular dichroism spectroscopy. Apart from the electrostatic interaction, the possible hydrophobic interaction between the liposomes and DNA was also taken into account for the observed deintercalation. The successful uptake of drug molecules by liposomes from the drug-DNA complex in the post-release period was also confirmed using confocal laser scanning microscopy (CLSM).

DNA Nanogels To Snare Carcinogens: A Bioinspired Generic Approach with High Efficiency.

Polycyclic aromatic hydrocarbons (PAHs) are combustion-related pollutants and are ubiquitous in the environment, including in sources of drinking water. Upon contact with DNA, stable PAH-DNA adducts form rapidly as the first step towards their toxic effects. In this work, we prepared hydrophilic DNA nanogels to exploit this generic complexation process as a biomimetic scavenging method. This approach relies on interaction between PAHs and the complete network that constitutes the water-swollen nanogels, and is not restricted to interfacial adsorption. Up to 720 µg of PAH per gram of DNA nanogel are taken up, meaning that 1 mg of DNA nanogel is sufficient to purify a liter of water containing the critical PAH concentration for cancer risk (600 ng L(-1) ). As a result of short diffusion pathways, PAH uptake is rapid, reaching 50 % loading after 15 minutes. Beyond PAHs, DNA nanogels may be useful for the generic detoxification of water containing genotoxins, since most known molecules that strongly associate with DNA are mutagenic.

Formation of DNA-copolymer fibrils through an amyloid-like nucleation polymerization mechanism.

Conjugation of a hydrophobic poly(2-oxazoline) bearing tertiary amide groups along its backbone with a short single stranded nucleotide sequence results in an amphiphilic comb/graft copolymer, which organizes in fibrils upon direct dissolution in water. Supported by circular dichroism, atomic force microscopy, transmission electron microscopy, and scattering data, fibrils are formed through inter- and intramolecular hydrogen bonding between hydrogen accepting amide groups along the polymer backbone and hydrogen donating nucleic acid grafts leading to the formation of hollow tubes.

Unbalanced estrogen metabolism in ovarian cancer.

Greater exposure to estrogens is a risk factor for ovarian cancer. To investigate the role of estrogens in ovarian cancer, a spot urine sample and a saliva sample were obtained from 33 women with ovarian cancer and 34 age-matched controls. Thirty-eight estrogen metabolites, conjugates and DNA adducts were analyzed in the urine samples using ultraperformance liquid chromatography/tandem mass spectrometry, and the ratio of adducts to metabolites and conjugates was calculated for each sample. The ratio of depurinating estrogen-DNA adducts to estrogen metabolites and conjugates was significantly higher in cases compared to controls (p < 0.0001), demonstrating high specificity and sensitivity. DNA was purified from the saliva samples and analyzed for genetic polymorphisms in the genes for two estrogen-metabolizing enzymes. Women with two low-activity alleles of catechol-O-methyltransferase plus one or two high-activity alleles of cytochrome P450 1B1 had higher levels of estrogen-DNA adducts and were more likely to have ovarian cancer. These findings indicate that estrogen metabolism is unbalanced in ovarian cancer and suggest that formation of estrogen-DNA adducts plays a critical role in the initiation of ovarian cancer.

Enhanced loading and controlled release of antibiotics using nucleic acids as an antibiotic-binding effector in hydrogels.

Antibiotic delivery is important to treat bacterial infections, one of the most challenging health problems globally. This study explored the application of nucleic acids as an antibiotic-binding effector for antibiotic loading and release. The data showed that the partition coefficient of tetracycline increased proportionally to the oligonucleotide concentration ranging from 0 to 1 mM. Resultantly, the incorporation of the oligonucleotides led to enhanced tetracycline loading in the hydrogels. In addition to the enhanced drug loading, the oligonucleotides could slow the release of tetracycline from the hydrogels. Experiments were further carried out to examine the capability of oligonucleotide-functionalized hydrogels in the inhibition of bacterial growth. The results showed that the oligonucleotide-functionalized hydrogels had higher antibacterial efficiency. Moreover, after tetracycline release, the oligonucleotide-functionalized hydrogels could be refilled with fresh tetracycline to reproduce the capability of inhibiting bacterial growth. Therefore, nucleic acid oligonucleotides are a promising antibiotic-binding effector for hydrogel functionalization in antibiotic delivery.

Visible-light-responsive antibacterial activity of Au-incorporated TiO2 layers formed on Ti-(0-10)at%Au alloys by air oxidation.

Rutile TiO2 layers were formed on substrates of Ti-(0-10)at%Au alloys by a simple process of air oxidation, and their antibacterial activities were evaluated under visible-light irradiation (λ ≥ 400 nm). Au was introduced into the TiO2 layers on Ti-(1-10)at%Au alloys and existed as both metallic Au nanoparticles and dissolved Au3+ ions. The TiO2 layers that formed on Ti-5at%Au and Ti-10at%Au alloys exhibited visible-light photocatalytic activity, that is, degradation of stearic acid and antibacterial activity against Escherichia coli. These visible-light activities were attributed to the surface plasmon resonance of metallic Au nanoparticles and the decrease in bandgap energy caused by dissolved Au3+ ions. The formation of hydroxyl radicals observed under visible-light irradiation is attributable to antibacterial activity. From a cost perspective, a Ti-5at%Au alloy is more suitable as a substrate for the formation of a TiO2 layer with antibacterial properties than a Ti-10at%Au alloy. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 991-1000, 2019.

Interaction of Different Divalent Metal Ions with Lipid Bilayer: Impact on the Encapsulation of Doxorubicin by Lipid Bilayer and Lipoplex Mediated Deintercalation.

In this article, we investigate the influence of different metal ions (Ca2+, Mg2+, and Zn2+) on binding of an anticancer drug doxorubicin (DOX) to DMPC bilayer and lipoplex mediated deintercalation of DOX from DOX-DNA complex. Our study reveals that lipid bilayer in the presence of different metal ions displays much higher binding affinity toward DOX than bare lipid bilayer does. Further, this affinity for a particular metal ion increases linearly with metal ion concentration. The steady state and time-resolved fluorescence studies reveal that binding of DOX with lipid bilayer in the presence of different metal ions varies in the order of Ca2+> Mg2+> Zn2+. The rotational relaxation of DOX in the presence of different metal ions takes place in the same order. We explain these phenomena in the light of alteration of the physical properties brought about by metal ions. Moreover, we find that binding pattern of metal ions with lipid head groups influences the intake of DOX in lipid bilayer. We exploit the binding of DOX with bilayer to study the deintercalation of DOX from DOX-DNA complex. We observe that with increase in metal ion concentration the deintercalation increases. Among all metal ions, Ca2+ appears to be most effective in deintercalation compared to other metal ions. The time-resolved fluorescence anisotropy and circular dichroism measurements indicate that in the presence of Ca2+, lipid bilayer offer strongest interaction with DNA while the same is weakest for Zn2+. This explains the highest percentage of deintercalation of DOX from drug-DNA complex in the presence of Ca2+. Overall the present study demonstrates a new strategy that binding of drug molecules with lipid bilayer and deintercalation of the same from drug-DNA complex can be tuned by modulation of lipid bilayer with different metal ions and their concentration.

Which one performs better for targeted lung cancer combination therapy: pre- or post-bombesin-decorated nanostructured lipid carriers?

PURPOSE: The co-delivery of gene and drugs has the potential to treat cancer. The aim of this study was to compare post-bombesin decorated nanostructured lipid carriers (NLC) carrying both doxorubicin (DOX) and DNA with pre-bombesin decorated NLC for lung cancer therapy. METHODS: Post-bombesin decorated NLC were prepared by two steps. First, DOX and DNA-loaded NLC (DOX-DNA-NLC) was prepared. Second, Bombesin-NH2 (BN-NH2) was added into DOX-DNA-NLC to react with stearic acid-polyethylene glycol-COOH (SA-PEG-COOH) loaded in NLC. Pre-bombesin decorated NLC were prepared by two steps. First, Bombesin (BN)-conjugated ligands were synthesized. Second, DOX and DNA were loaded into BN decorated NLC. Their average size, zeta potential, drug and gene loading were evaluated. NCl-H460 human non-small lung cancer cells (NCl-H460 cells) were used for the testing of in vitro transfection efficiency and in vitro cytotoxicity. In vivo transfection efficiency and anti-tumor effect of NLC were evaluated on mice bearing NCl-H460 cells model. RESULTS: Post-bombesin decorated NLC has a particle size of 128 nm, DOX encapsulation efficiency (EE) of 85% and DNA EE of 91%. Pre-bombesin decorated NLC has a particle size of 101 nm, DOX EE of 86% and DNA EE of 92%. Post-bombesin decorated NLC displayed more stable and remarkably higher transfection efficiency and better anti-tumor ability than pre-bombesin decorated NLC both in vitro and in vivo. CONCLUSION: Post-bombesin decorated NLC could function as better carriers to improve the cell targeting and nuclear targeting ability. The resulting nanomedicine could be a promising active targeting drug/gene therapeutic system for lung cancer therapy.

RETRACTED: Low density lipoprotein receptor targeted doxorubicin/DNA-Gold Nanorods as a chemo- and thermo-dual therapy for prostate cancer.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the authors and sanctioned by the Editor-in-Chief. The authors found errors in the data presentation - apoptotic statistics and in vivo distribution - which makes the conclusion not representative. The authors express sincere apologies for the error and inconvenience to readers.

Characterization and transfection properties of lipoplexes stabilized with novel exchangeable polyethylene glycol-lipid conjugates.

The positive charge of cationic-lipid/DNA complexes (lipoplexes) renders them highly susceptible to interactions with the biological milieu, leading to aggregation and destabilization, and rapid clearance from the blood circulation. In this study we synthesized and characterized a set of novel amphiphiles, based on N-methyl-4-alkylpyridinium chlorides (SAINTs), to which a PEG moiety is coupled. Plasmids were fully protected in lipoplexes prepared from cationic SAINT-2 lipid and stabilized with SAINT-PEGs. Our results demonstrate that SAINT-PEG stabilization is transient, and permits DNA to be released from these lipoplexes. The rate of SAINT-PEG transfer from lipoplexes to acceptor liposomes was determined by the nature of the lipid anchor. Increased hydrophobicity, by lengthening the alkyl chain, resulted in a decrease of the rate of DNA release from the lipoplexes. Chain unsaturation had the opposite effect. Similarly, the in vitro transfection potency of lipoplexes containing PEG-SAINT derivatives was sensitive to the length and (un)saturation of the alkyl chain. However, the internalization of SAINT-PEG stabilized lipoplexes is determined by their charge, rather than by the concentration of the polymer conjugate. Lipoplexes targeted to cell-surface epithelial glycoprotein 2, by means of a covalently coupled monoclonal antibody, were specifically internalized by cells expressing this antigen.

Possible mechanism of polycation liposome (PCL)-mediated gene transfer.

A novel gene transfer system utilizing polycation liposomes (PCLs), obtained by modifying liposomes with cetyl polyethylenimine (PEI), was previously developed (Gene Ther. 7 (2002) 1148). PCLs show notable transfection efficiency with low cytotoxicity. However, the mechanism of PCL-mediated gene transfer is still unclear. In this study, we examined the intracellular trafficking of PCL-DNA complexes by using HT1080 cells, fluorescent probe-labeled materials, and confocal laser scan microscopy. We found that the PCL-DNA complexes were taken up into cells by the endosomal pathway, since both cellular uptake of the complex and gene expression were blocked by wortmannin, an inhibitor of this pathway. We also observed that the plasmid DNA and cetyl PEI complex became detached from the PCL lipids and was preferentially transferred into the nucleus in the form of the complex, whereas the PCL lipids remained in the cytoplasmic area, possibly in the endosomes. In fact, nigericin, which dissipates the pH gradient across the endosomal membrane, inhibited the detachment of lipids from the PCL-DNA complex and subsequent gene expression. Taken together, our data indicate the following mechanism for gene transfer by PCLs: PCLs effectively transfer DNA to endosomes and release cetyl PEI-DNA complexes into the cytosol. Furthermore, cetyl PEI also contributes to gene entry into the nucleus.

Influence of formulation parameters on the characteristics of poly(D, L-lactide-co-glycolide) microspheres containing poly(L-lysine) complexed plasmid DNA.

This study describes the influence of polymer type, surfactant type/concentration, and target drug loading on the particle size, plasmid DNA (pDNA) structure, drug loading efficiency, in vitro release, and protection from DNase I degradation of poly(D, L-lactide-co-glycolide) (PLGA) microspheres containing poly(L-lysine) (PLL) complexed pDNA. PLGA microspheres containing pDNA-PLL were prepared using the water-in-oil-in-water (w-o-w) technique with poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) as surfactants in the external aqueous phase. A complex ratio of 1:0.33 (pDNA-PLL, w/w) enhanced the stability of pDNA during microsphere preparation. Higher pDNA-PLL loading efficiency (46.2%) and supercoiled structure (64.9%) of pDNA were obtained from hydrophobic PLGA (M(w) 31000) microspheres compared with hydrophilic PLGA or low-molecular-weight PLGA microspheres. The particle size decreased from 6.6 to 2.2 microm when the concentration of PVA was increased from 1 to 7%. At the same concentration of surfactant, PVA stabilized microspheres showed higher pDNA-PLL loading efficiency (46.2%) than PVP stabilized microspheres (24.1%). Encapsulated pDNA in PLGA microspheres was protected from enzymatic degradation and maintained in the supercoiled form. The pDNA-PLL microspheres showed in vitro release of 95.9 and 84.9% within 38 days from the low-molecular-weight PLGA and hydrophilic PLGA microspheres, respectively, compared to 54.2% release from the hydrophobic, higher-molecular-weight PLGA microspheres. The results suggest loading and release of pDNA-PLL complex can be influenced by surfactant concentration and polymer type.

Nitrite curing of chicken, pork, and beef inhibits oxidation but does not affect N-nitroso compound (NOC)-specific DNA adduct formation during in vitro digestion.

Uncured and nitrite-cured chicken, pork, and beef were used as low, medium, and high sources of heme-Fe, respectively, and exposed to an in vitro digestion model simulating the mouth, stomach, duodenum, and colon. With increasing content of iron compounds, up to 25-fold higher concentrations of the toxic lipid oxidation products malondialdehyde, 4-hydroxy-2-nonenal, and other volatile aldehydes were formed during digestion, together with increased protein carbonyl compounds as measurement of protein oxidation. Nitrite curing of all meats lowered lipid and protein oxidation to the level of oxidation in uncured chicken. Strongly depending on the individual fecal inoculum, colonic digestion of beef resulted in significantly higher concentrations of the NOC-specific DNA adduct O(6)-carboxymethyl-guanine compared to chicken and pork, whereas nitrite curing had no significant effect. This study confirms previously reported evidence that heme-Fe is involved in the epidemiological association between red meat consumption and colorectal cancer, but questions the role of nitrite curing in this association.

A core cross-linked polymeric micellar platium(IV) prodrug with enhanced anticancer efficiency.

A core cross-linked polymeric micellar cisplatin(IV) conjugate prodrug is prepared by attaching the cisplatin(IV) to mPEG-b-PLL biodegradable copolymers to form micellar nanoparticles that can disintegrate to release the active anticancer agent cisplatin(II) in a mild reducing environment. Moreover, in vitro studies show that this cisplatin(IV) conjugate prodrug displays enhanced cytotoxicity against HepG2 cancer cells compared with cisplatin(II). Further studies demonstrate that the high cellular uptake and platinum-DNA adduct of this cisplatin(IV) conjugate prodrug can induce more cancer-cell apoptosis than cisplatin(II), which is responsible for its enhanced anticancer activity.

Functionalized nanostructures: redox-active porphyrin anchors for supramolecular DNA assemblies.

We have synthesized and studied a supramolecular system comprising a 39-mer DNA with porphyrin-modified thymidine nucleosides anchored to the surface of large unilamellar vesicles (liposomes). Liposome porphyrin binding characteristics, such as orientation, strength, homogeneity, and binding site size, was determined, suggesting that the porphyrin is well suited as a photophysical and redox-active lipid anchor, in comparison to the inert cholesterol anchor commonly used today. Furthermore, the binding characteristics and hybridization capabilities were studied as a function of anchor size and number of anchoring points, properties that are of importance for our future plans to use the addressability of these redox-active nodes in larger DNA-based nanoconstructs. Electron transfer from photoexcited porphyrin to a lipophilic benzoquinone residing in the lipid membrane was characterized by steady-state and time-resolved fluorescence and verified by femtosecond transient absorption.

Polycationic protamine for water-insoluble complex formation with DNA.

The DNA/protamine complex was prepared by a reaction between DNA and protamine sulfate solutions with stirring, and its cell viability, antibacterial effect and histopathological responses were examined. A water-insoluble white powder, DNA/protamine complex, with a porous structure was obtained. The molar binding ratio of the complex prepared from a solution containing equal amounts of DNA and protamine sulfate by weight was 0.038 and the efficiency of complex formation was 61%. In a cell culture test using MC-3T3-E1 mouse osteoblast cells, the complex showed less cytotoxicity than protamine sulfate alone and cell viabilities were more than 98%. A porous disk could be prepared easily and showed an antibacterial effect against Staphyrococcus aureus, Porphyromonas gingivalis and Prevotella intermedia in an antibacterial sensitivity test and a mild tissue response in vivo test. These results suggested that the DNA/protamine complex could be a useful biodegradable biomaterial with antibacterial effects.

Separation and sequencing of isomeric oligonucleotide adducts using monolithic columns by ion-pair reversed-phase nano-HPLC coupled to ion trap mass spectrometry.

An ion-pair reversed-phase nano-high-performance liquid chromatography (IP-RP-nano-HPLC) method using a monolithic poly(styrene-divinylbenzene) (PS-DVB) column coupled to nanoelectrospray ionization mass spectrometry (nano-ESI-MS) was evaluated to separate and identify isomeric oligonucleotide adducts derived from the covalent binding of (+/-)-anti-7r,8t-dihydroxy-9t,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene [(+/-)-anti-BPDE] to double-stranded (ds) 5'-PO4--ACCCGCGTCCGCGC-3'/5'-GCGCGGGCGCGGGT-3' oligonucleotide. The influence of three different nanospray emitters on electrospray signal was evaluated in terms of analyte ion sensitivity. The best nanoelectrospray performance for the oligonucleotides was observed with the distal metal-coated emitter. The performance of three different stationary phases was also investigated. The chromatographic separation performance of the polymeric monolithic PS-DVB stationary phase significantly surpassed that of columns packed with the microparticulate sorbents C18 or PS-DVB. Different mobile phase organic solvents and ion-pairing reagents were also evaluated. An optimized mobile phase consisting of methanol and 25 mM triethylammonium bicarbonate resulted in the best chromatographic resolution and increased MS sensitivity of the oligonucleotides. By using a monolithic PS-DVB stationary phase fabricated in a nanocolumn, four positional isomeric (+/-)-BPDE-oligonucleotide adducts were separated and identified. In addition to four of the possible five positional isomers, three positional isomers were also resolved to several diastereoisomers, although their stereostructures could not be identified in the absence of reference standards.

Integrated microfluidic device with an electroplated palladium decoupler for more sensitive amperometric detection of the 8-hydroxy-deoxyguanosine (8-OH-dG) DNA adduct.

8-hydroxy-deoxyguanosine (8-OH-dG) DNA adduct is one of the most frequently used biomarkers reporting on the oxidative stress that leads to DNA damage. More sensitive and reliable microfluidic devices are needed for the detection of these biomarkers of interest. We have developed a capillary electrophoresis (CE)-based microfluidic device with an electroplated palladium decoupler that provides significantly improved detection limit, separation efficiency, and resolving power. The poly(dimethylsiloxane) (PDMS)/glass hybrid device has fully integrated gold microelectrodes covered in situ with palladium nanoparticles using an electroplating technique. The performance and coverage of the electrodes electroplated with palladium particles were evaluated electrochemically and via scanning electron microscope (SEM) imaging, respectively. The performance of the device was tested and evaluated with different buffer systems, pH values, and electric field strengths. The results showed that this device has significantly improved resolving power, even at separation electric field strengths as high as 600 V cm-1. The detection limit for the 8-OH-dG adduct is about 20 attomoles; the concentration limit is on the order of 100 nM (S/N=3). A linear response is reported for both 8-OH-dG and dG in the range from 100 nM to 150 microM (approximately 100 pA microM-1) with separation efficiencies of approximately 120,000-170,000 plates m-1.