Salmon Testes DNA Research Articles

The investigation of inclusion behavior of Solvent Violet 9 with 4-sulfonatocalix[n]arenes and its recognition to DNA

The inclusion behavior of Solvent Violet 9 (SV9) with 4-sulfonatocalix[n]arenes (SCXn) (n=4,6,8) was investigated at various pH values by ultraviolet–visible spectroscopy. SV9 is able to form an inclusion complex with calixarenes. Different absorption behaviors were observed for the dye with the various host calixarenes. The molecular binding abilities were affected by the configuration of the calixarene cavities and the solution pH. Various experimental conditions, including calixarenes concentrations, were investigated and the results suggested that the three calixarene were most suitable for inclusion of the dye at pH=3.05. The formation constant could be calculated. The inclusion behavior of the complexes was studied in detail using nuclear magnetic resonance spectroscopy. Finally, the interactions of SV9 with Salmon testes DNA in SCXn supramolecular system were studied by UV–Vis absorption spectroscopy. The UV–Vis absorption show that the interaction of SV9 with DNA depends on the concentration ratio of SV9 to DNA and the pH values. The binding constants of inclusion complexes with DNA are calculated. It was observed that SCXn can affect the interactive mode of SV9 with DNA.

Mechanistic and Catalytic Studies of β-Nitroalcohol Crosslinking with Polyamine.

β-Nitroalcohols (βNAs) are promising corneoscleral crosslinking agents for the treatment of diseases such as keratoconus and myopia. Although it is believed that formaldehyde is released from the crosslinking reactions of βNAs, the mechanism by which βNAs react with amine-functionalized polymers has yet to be known. In this study, we present the reaction mechanism of the βNA crosslinking. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) data provide strong evidence that formaldehyde is released during the reaction. Catalytic studies show that sodium bicarbonate (NaHCO3) and salmon testes DNA accelerate the reaction while hydroxynitrile lyase from Arabidopsis thaliana decelerates the crosslinking reaction. These results suggest that βNAs are potential self-administered crosslinking agents for future clinical use.

Changes in the infrared microspectroscopic characteristics of DNA caused by cationic elements, different base richness and single-stranded form.

BackgroundThe infrared (IR) analysis of dried samples of DNA and DNA-polypeptide complexes is still scarce. Here we have studied the FT-IR profiles of these components to further the understanding of the FT-IR signatures of chromatin and cell nuclei.Methodology/Principal FindingsCalf thymus and salmon testis DNA, and complexes of histone H1, protamine, poly-L-lysine and poly-L-arginine (histone-mimic macromolecules) with DNA were analyzed in an IR microspectroscope equipped with an attenuated total reflection diamond objective and Grams software. Conditions including polypeptides bound to the DNA, DNA base composition, and single-stranded form were found to differently affect the vibrational characteristics of the chemical groups (especially, PO2 −) in the nucleic acid. The antisymmetric stretching (νas) of the DNA PO2 − was greater than the symmetric stretching (νs) of these groups and increased in the polypeptide-DNA complexes. A shift of the νas of the DNA PO2 − to a lower frequency and an increased intensity of this vibration were induced especially by lysine-rich histones. Lysine richness additionally contributed to an increase in the vibrational stretching of the amide I group. Even in simple molecules such as inorganic phosphates, the vibrational characteristics of the phosphate anions were differently affected by different cations. As a result of the optimization of the DNA conformation by binding to arginine-rich polypeptides, enhancements of the vibrational characteristics in the FT-IR fingerprint could be detected. Although different profiles were obtained for the DNA with different base compositions, this situation was no longer verified in the polypeptide-DNA complexes and most likely in isolated chromatin or cell nuclei. However, the νas PO2 −/νs PO2 − ratio could discriminate DNA with different base compositions and DNA in a single-stranded form.Conclusions/SignificanceFT-IR spectral profiles are a valuable tool for establishing the vibrational characteristics of individualized chromatin components, such as DNA and DNA-polypeptide complexes in dried samples.

Determination of ligand to DNA binding parameters from two-dimensional DSC curves

The application of the theory of DNA denaturation linked to ligand binding to differential scanning calorimetry (DSC) is a useful tool to simultaneously characterize the energetics of denaturation and binding. Although the general theory is well known, the current DSC-based approaches to study the DNA–ligand interaction do not utilize the full potential of this method. In this paper, we propose the analytical approach for detailed analysis of DNA–ligand interaction from DSC data. The DNA macromolecule is represented as an assembly of cooperative units which melt by two-state model. The explicit account of ligand distribution on polymeric DNA and the temperature dependences of melting and binding constants, as well as of enthalpies, are considered. Such approach enables to extract the binding constant, stoichiometry, enthalpy, entropy, and heat capacity changes from multiple excess heat capacity profiles obtained at varying concentrations of the ligand (i.e. two-dimensional DSC curves). The applicability of the developed approach was demonstrated using an example salmon testes DNA–proflavine DSC experiment. The full set of DNA melting and proflavine binding thermodynamic parameters was obtained. Comparison of the proflavine binding parameters obtained from DSC with those determined from alternative experimental methods has proved the usefulness of the DSC method for evaluation of the binding thermodynamics in DNA–ligand system. In addition, the approach developed in the present study, allows to evaluate the concentration dependences of all species in solution as a function of temperature. Analysis of these dependences has enabled to interpret fine effects on the DSC curves of DNA–ligand complexes.

Surface morphology of hybrids of double-stranded DNA and single-walled carbon nanotubes studied by atomic force microscopy

We examined the formation of hybrids of double-stranded DNA (dsDNA) and single-walled carbon nanotubes (SWNTs), which has not been well investigated yet. In particular, the adsorption of dsDNA onto SWNT produced by chemical vapor deposition (CVD) was examined for the first time. When small amount of dsDNA was mixed with CVD SWNT, well dispersed hybrids with smooth surfaces were observed by atomic force microscopy (AFM). Through a comparison of dsDNA, single-stranded DNA (ssDNA), CVD SWNT, and high-pressure carbon monoxide process (HiPco) SWNT, we found that the surface morphology of the hybrids was independent of the DNA type. Even when sonicated salmon testes DNA, which has a random sequence and length, was employed, smooth surfaces were obtained on the dsDNA–CVD hybrids as well as on the ssDNA–CVD hybrids. The ratio of monodispersed SWNT and bundled SWNT in a dispersion solution was also not affected by the DNA type. In contrast, the quantity of the fabricated hybrids was affected by the types of DNA especially when HiPco SWNT was used. Our results indicated that characteristic features of the dsDNA–CVD hybrids and provide an enhanced understanding of the adsorption mechanism of dsDNA onto SWNTs.

Genomic salmon testes DNA as a catalyst for Michael reactions in water

The DNA molecule, recognized as the carrier of genetic information in vivo, can function as an efficient organocatalyst for Michael additions of 1,3-dicarbonyl compounds to activated alkenes in aqueous media. The procedure described here is environmentally benign and offers several advantages in terms of simplicity, generality and efficiency. We have used fluorescence spectroscopy to evaluate the catalytic activity of a molecule of DNA.

Altered expression of microRNA miR-146a correlates with the development of chronic renal inflammation

MicroRNAs (miRNAs) are highly conserved small non-coding RNAs that act as post-transcriptional regulators of target mRNA. In this study, we sought to identify the microRNA underlying local inflammation in a murine model of chronic kidney disease (CKD). In microarray analysis of kidneys, the expression of miR-146a/b was elevated in B6.MRLc1 CKD mice that spontaneously develop renal inflammation with age. Primary-microRNA analysis found that elevated miR-146a/b expression in the kidneys of B6.MRLc1 mice was mainly derived from miR-146a rather than miR-146b, and this expression increased with the development of CKD. Histopathological scores for glomerular and interstitial lesions, mRNA expression of inflammatory mediators, and macrophage infiltration were significantly higher in B6.MRLc1 than C57BL/6 mice and were positively correlated with miR-146a expression. In situ hybridization and laser microdissection-RT-PCR showed that miR-146a expression in interstitial lesions containing inflammatory cells was higher than in the glomerulus. The increased expression of the inflammatory-associated genes RELA, IRAK1, IL1B, IL10, and CXCLs was noted in miR-146a/b-silenced human monocytes. The amount of miR-146a was higher in urine sediments of B6.MRLc1 than of C57BL/6 mice. Thus, miR-146a expression in the kidneys and its urinary excretion was specifically associated with the development of interstitial lesions and correlated with inflammatory cell infiltration.

Structure and stability of the complex formed by oligonucleotides

Polycations and cationic lipids have been widely used as non-viral vectors for the delivery of plasmid DNA, siRNA and anti-sense oligonucleotides. To demonstrate that one polycation can form a complex with several types of DNA, we conducted a comparative study on the complexation of poly(L-lysine) (PLL) with 2000 bp salmon testes DNA (dsDNA), 21 bp double-stranded oligonucleotides (ds-oligo), and 21 nt single-stranded oligonucleotides (ss-oligo) in PBS buffer. The complexes are prepared by a titration method and the process is monitored by laser light scattering. It was found that in most cases, ss-oligo and ds-oligo form complexes with higher molecular weights than the complex formed by dsDNA at the same +/- ratio immediately after mixing. More importantly, the complexes formed by oligonucleotides are not stable, the scattered intensity gradually decreases to the level of the solvent in weeks. Atomic force microscopy measurements also indicate that the freshly prepared complex is subject to environmental changes and could dissociate very quickly. The behaviour of oligonucleotides cannot be predicted by the classical polyelectrolyte theories.

Selective Derivatization of Cytosine and Methylcytosine Moieties with 2-Bromoacetophenone for Submicrogram DNA Methylation Analysis by Reversed Phase HPLC with Spectrofluorimetric Detection

In eukaryotes, actual DNA methylation patterns provide biologically important information, for which both, genome-wide and locus-specific methylation at cytosine residues have been extensively studied. The original contribution of this work relies on the selective derivatization of cytosine moieties with 2-bromoacetophenone for the determination of global DNA methylation by reversed phase high performance liquid chromatography with spectrofluorimetric detection. The important features of the proposed procedure are as follows: (1) no need for the elimination of RNA, (2) detection limits for cytidine, 2'-deoxycytidine, 5-methylcytidine, and 5-methyl-2'-deoxycytidine in the range of 14.4-22.7 fmol, (3) feasibility for the detection of 0.06% of methylation in a low amount of DNA (80 ng), (4) potential viability for the evaluation of RNA methylation, and (5) relative simplicity in terms of analytical instrumentation and personnel training. The results obtained in the analysis of salmon testes DNA and nucleic acids from plant, human blood, and earthworms demonstrate the utility of the proposed procedure in biological studies and, in particular, for evaluation of the potential effect of environmental factors on actual DNA methylation in different types of living organisms.

EnantioselectivesynHydration of Enones in Water Using a DNA-Based Catalyst

In this paper, the authors report the first non-enzymatic hydration of α,β-unsaturated ketones in water, which proceeds in an enantio­selective (up to 82% ee) and diastereospecific fashion (exclusive syn addition). The catalytic ­system consists of st-DNA (salmon testes DNA, approximately 2000 base pairs long) and a copper complex bound by non-covalent interactions (ligand L1 provided the optimum results). The individual components (DNA, ligand, Cu²+) have specific functions, which are synergistic; DNA serves as a chiral inductor, the presence of copper is crucial for the catalysis to occur, and the ligand tunes the interactions leading to higher reactivity and enantioselectivity.

Specific Detection of Banana Residue in Processed Foods Using Polymerase Chain Reaction

Specific polymerase chain reaction (PCR) methods were developed for the detection of banana residue in processed foods. For high banana specificity, the primer set BAN-F/BAN-R was designed on the basis of the large subunit of ribulose-1,5-bisphosphate carboxylase (rbcL) genes of chloroplasts and used to obtain amplified products specific to banana by both conventional and real-time PCR. To confirm the specificity of these methods, genomic DNA samples from 31 other species were examined; no amplification products were detected. Subsequently, eight kinds of processed foods containing banana were investigated using these methods to confirm the presence of banana DNA. Conventional PCR had a detection limit of 1 ppm (w/w) banana DNA spiked in 50 ng of salmon testis DNA, whereas SYBR Green I real-time semiquantitative PCR had a detection limit as low as 10 ppm banana DNA. Thus, both methods show high sensitivity and may be applicable as specific tools for the detection of trace amounts of banana in commercial food products.

Detection and quantitation of N-(deoxyguanosin-8-yl)-2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine adducts in DNA using online column-switching liquid chromatography tandem mass spectrometry

The heterocyclic aromatic amine, 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP) is formed by the grilled cooking of certain foods such as meats, poultry and fish. PhIP has been shown to induce tumours in the colon, prostate and mammary glands of rats and is regarded as a potential human dietary carcinogen. PhIP is metabolically activated via cytochrome P450 mediated oxidation to an N-hydroxylamino-PhIP intermediate that is subsequently converted to an ester by N-acetyltransferases or sulfotransferases and undergoes heterolytic cleavage to produce a PhIP-nitrenium ion, which reacts with DNA to form the N-(deoxyguanosin-8-yl)-2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP-C8-dG) adduct. Thus far, the detection and quantification of PhIP-DNA adducts has relied to a large extent on 32P-postlabelling methodologies. In order to expand the array of available techniques for the detection and improved quantification of PhIP-C8-dG adducts in DNA we have developed an online column-switching liquid chromatography (LC)–electrospray ionization (ESI)-tandem mass spectrometry (MS/MS) selected reaction monitoring (SRM) method incorporating an isotopically [ 13C 10]-labelled PhIP-C8-dG internal standard for the analysis of DNA enzymatically hydrolysed to 2′-deoxynucleosides. A dose-dependent increase was observed for PhIP-C8-dG adducts when salmon testis DNA was reacted with N-acetoxy-PhIP. Analysis of DNA samples isolated from colon tissue of mice treated by oral gavage daily for 5 days with 50 mg/kg body weight of PhIP resulted in the detection of an average level of 14.8 ± 3.7 PhIP-C8-dG adducts per 10 6 2′-deoxynucleosides. The method required 50 μg of hydrolysed animal DNA on column and the limit of detection for PhIP-C8-dG was 2.5 fmol (1.5 PhIP-C8-dG adducts per 10 8 2′-deoxynucleosides). In summary, the LC–ESI-MS/MS SRM method provides for the rapid automation of the sample clean up and a reduction in matrix components that would otherwise interfere with the mass spectrometric analysis, with sufficient sensitivity and precision to analyse DNA adducts in animals exposed to PhIP.

Methylene Blue Interactions with Chromosomal and Plasmid DNA on Screen‐Printed Carbon Electrodes

AbstractMethylene blue (MB) is a typical photosensitizing agent and a DNA hybridization indicator, but its modes of interaction with the DNA molecules are not clearly described, particularly in relation to its electrochemical oxidation signals. To probe the DNA‐MB interactions we have used chromosomal salmon testes and supercoiled plasmid sc pUC19 DNA immobilized on home‐made screen‐printed electrodes (SPEs) and a wide range of MB concentrations, from nano‐ to micromolar. The applicability of the home‐made screen‐printed electrodes used for the DNA‐MB studies were tested using standard calf thymus DNA. Two MB oxidation peak signals: MB(I) at ca. −0.18 V and MB(II) at 0 V vs. Ag/AgCl were detected within ±10–15% standard deviation, signals different from adsorbed MB signal (−0.25 V, pH 4.7). The MB(I) signal, seen when both DNAs were used, showed two plateaus, one at nano‐ and another at micromolar MB concentrations; these were accompanied by the changes in the oxidation signal at 0.98 V, usually attributed to guanine oxidation. In contrast, the MB(II) signal was only seen for salmon testes DNA, indicating various modes of MB interactions with chromosomal and plasmid DNA. In the presence of MB, the guanine related signal (G) at 0.98 V has been amplified significantly (10×), allowing for the identification of the DNAs at low DNA concentrations, the feature particularly useful in the plasmid sc pUC19 detection. The use of another DNA intercalator, riboflavin (RF), aided in the identification of the relation between MB(I), MB(II) and G oxidation signals.

DNA‐Based Hybrid Catalysts for Asymmetric Organic Synthesis

Stereoselective hybrid systems based on metal-assisted catalysis with a chiral biomacromolecule form an attractive research area for the synthesis of enantiomerically pure compounds. Although various methods are available for this purpose, most rely on the use of enzymes, proteins, or RNA. The application of DNA-based hybrid catalysts for enantioselective synthesis emerged only a few years ago. DNA-based hybrid catalysts have been self-assembled from DNA and a metal complex with a specific ligand through supramolecular or covalent anchoring strategies and have demonstrated high stereoselectivity and rate enhancement in Lewis acid catalyzed reactions, such as Diels-Alder, Michael addition, and Friedel-Crafts reactions. For these reactions, cheap and commercially available salmon testes DNA has generally been used. In this Minireview, we summarize recent developments in the area of asymmetric catalysis with DNA-based hybrid catalysts.

Phenothiazine: An Effective Molecular Adhesive for Protein Immobilization

Protein immobilization is imperative for bioengineering and biochemical applications. Although many excellent approaches have been proposed, most require elaborate skills and labor-intensive techniques. In this work, we report that phenothiazine compounds such as thionine chloride (TC) are potential molecular adhesives for protein immobilization. According to conductive-mode atomic force microscopic analysis (C-AFM), TC exists with a specific affinity for proteins and can be modified on solid surfaces like ITO glass squares (denoted ITO|TC) via a simple diazotization-reduction process. Because the affinity is ∼200 nN, equivalent to 102 C−C single bonds, a variety of proteins including glucose oxidase (GOx), glucose dehydrogenase (GDH), ferritin (FT), bovine serum albumin (BSA), and salmon testes DNA (DNA) can thus be immobilized on ITO through TC. Most proteins, however, behave like insulators in aqueous solutions (0.1 M KCl). For this reason, the protein-treated ITO|TC electrodes exhibited insignificant ...

Phosphorus and osmium as elemental tags for the determination of global DNA methylation—A novel application of high performance liquid chromatography inductively coupled plasma mass spectrometry in epigenetic studies

The hyphenation of high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC–ICP-MS) is proposed in this work as a novel approach for the evaluation of DNA methylation, defined as the ratio between methylated cytosine and total cytosine bases in DNA. In the first part, reversed phase separation of 5-methyl-2′-deoxycytidine monophosphate (5mdCMP) and four deoxynucleotides with specific ICP-MS detection on 31P had been explored. In further development, selective labeling of 5-methylcytosine in ssDNA was carried out using potassium osmate (K 2OsO 4) in the presence of strong oxidant (K 3Fe(CN) 6) and N, N, N′, N′-tetramethylethylenediamine (TEMED). The sample was then cleaned up and introduced to size exclusion chromatography–ICP-MS for specific detection at 31P and 189Os and for evaluation of the molar ratio between Os and P eluted in DNA molecular mass fraction. The quantification of the two elemental tags was achieved by external calibration with phosphoric acid and Os(VI)-TEMED, respectively. The amount of Os in DNA fraction corresponded to methylated cytosines, while P signal was directly proportional to the total amount of DNA and could be recalculated to the amount of cytosine bases. The two procedures were tested by analyzing salmon testes DNA and a commercial oligonucleotide of known composition. For comparative purposes, these same samples were digested to deoxynucleosides and analyzed by reversed phase HPLC with spectrophotometric detection (DAD) at 280 nm. The results obtained using two procedures based on ICP-MS detection were in good agreement and also in agreement with the results obtained by HPLC–DAD procedure. In conclusion, ICP-MS specific detection at internal or external element tags seems to be an interesting alternative for the evaluation of global DNA in epigenetic studies.

Quantification of 3-Nitrobenzanthrone-DNA Adducts Using Online Column-Switching HPLC-Electrospray Tandem Mass Spectrometry

The aromatic nitroketone 3-nitrobenzanthrone (3-nitro-7H-benz[de]anthracen-7-one; 3-NBA) is an extremely potent mutagen and a suspected human carcinogen detected in the exhaust of diesel engines and in airborne particulate matter. 3-NBA is metabolically activated via reduction of the nitro group to the hydroxylamine (N-OH-3-ABA) to form covalent DNA adducts. Thus far, the detection and quantification of covalent 3-NBA-DNA adducts has relied solely on (32)P-postlabeling methodologies. In order to expand the range of available techniques for the detection and improved quantification of 3-NBA-DNA adducts, we have developed a method based upon online column-switching HPLC coupled to electrospray tandem mass spectrometry, with isotopic dilution of (15)N-labeled internal standards. This methodology was applied to the determination of three 3-NBA-derived adducts: 2-(2'-deoxyguanosin-N(2)-yl)-3-aminobenzanthrone (dG-N(2)-3-ABA), N-(2'-deoxyguanosin-8-yl)-3-aminobenzanthrone (dG-C8-N-3-ABA) and 2-(2'-deoxyguanosine-8-yl)-3-aminobenzanthrone (dG-C8-C2-3-ABA). Dose-dependent increases were observed for all three adducts when salmon testis DNA was reacted with N-acetoxy-3-aminobenzanthrone (N-AcO-3-ABA). dG-C8-C2-3-ABA was detected at much lower levels (overall 1%) than the other two adducts. DNA samples isolated from tissues of rats treated either intratracheally with 3-NBA or intraperitoneally with N-OH-3-ABA were analyzed by mass spectrometry, and the results compared to those obtained by (32)P-postlabeling. The method required 50 microg of hydrolyzed animal DNA on column and the limit of detection was 2.0 fmol for each adduct. dG-C8-C2-3-ABA was not observed in any of the samples providing confirmation that it is not formed in vivo. Linear regression analysis of the levels of dG-N(2)-3-ABA and dG-C8-N-3-ABA in the rat DNA showed a reasonable correlation between the two methods (R(2) = 0.88 and 0.93, respectively). In summary, the mass spectrometric method is a faster, more automated analytical approach that also provides structural confirmation of the adducts detected by (32)P-postlabeling, and it has sufficient sensitivity and precision to analyze DNA adducts in animals exposed to 3-NBA or its hydroxylamine metabolite.

Characterization of a Functional ZBP-89 Binding Site That Mediates Gata1 Gene Expression during Hematopoietic Development

GATA-1 is a lineage-restricted transcription factor that plays essential roles in hematopoietic development. The Gata1 gene hematopoietic enhancer allowed Gata1 reporter expression in erythroid cells and megakaryocytes of transgenic mice. The Gata1 hematopoietic enhancer activity is strictly dependent on a GATA site located in the 5' region of the enhancer. However, the importance of the GC-rich region adjacent to the 3'-end of this GATA site has been also suggested. In this study, we show that this GC-rich region contains five contiguous deoxyguanosine residues (G(5) string) that are bound by multiple nuclear proteins. Interestingly, deletion of one deoxyguanosine residue from the G(5) string (G(4) mutant) specifically eliminates binding to ZBP-89, a Krüppel-like transcription factor, but not to Sp3 and other binding factors. We demonstrate that GATA-1 and ZBP-89 occupy chromatin regions of the Gata1 enhancer and physically associate in vitro through zinc finger domains. Gel mobility shift assays and DNA affinity precipitation assays suggest that binding of ZBP-89 to this region is reduced in the absence of GATA-1 binding to the G1HE. Luciferase reporter assays demonstrate that ZBP-89 activates the Gata1 enhancer depending on the G(5) string sequence. Finally, transgenic mouse studies reveal that the G(4) mutation significantly reduced the reporter activity of the Gata1 hematopoietic regulatory domain encompassing an 8.5-kbp region of the Gata1 gene. These data provide compelling evidence that the G(5) string is necessary for Gata1 gene expression in vivo and ZBP-89 is the functional trans-acting factor for this cis-acting region.

Friedel-Crafts Alkylation of Indoles with a Cu-DNA Catalyst

An impressive example of an enantioselective Friedel-Crafts reaction using water and a DNA-based catalyst is described. The catalyst is assembled in situ from Cu-dmbpy and salmon testes DNA, which is readily available and inexpensive. The reaction is compatible with a ­variety of substituents on the indole and olefin, ­although in some cases, using other DNA strands provided more optimal results. Results for both analytical and preparative scales are reported.

DNA/chitosan nanocomplex as a novel drug carrier for doxorubicin

The present study was to investigate the potentials of DNA/chitosan nanocomplexes as a carrier for small drug delivery. Two highly water-soluble chitosans (87 kDa and 18 kDa) were prepared and labeled with fluorescein isothiocyanate (FITC). DNA/chitosan nanocomplexes were prepared by mixing salmon testes DNA and the FITC labeled chitosan (FITC-chitosan) and their biophysical properties and biodistribution in vivo were then investigated. The molecular weight of chitosan and the ratio of the positive amino group of chitosan to the negative phosphate group of DNA (N/P ratio) influenced the physical properties of the nanocomplexes. The fluorescence intensity of both types of the free FITC-chitosan decreased rapidly within 4 hr post-injection. In contrast, the DNA/chitosan nanocomplexes were accumulated in the liver and kidneys and remained at a relatively high stable level in these tissues and in blood up to 24 hr post-injection. This study also assessed the stability of the anti-cancer drug doxorubicin (DOX) when it was conjugated to chitosan to form a chitosan-doxorubicin conjugate (chi-DOX), which was then mixed with DNA to form a DNA/chitosan-doxorubicin nanocomplex (DNA/chi-DOX). Both the chi-DOX and DNA/chi-DOX complexes exerted cytotoxic effects on HeLa, HepG2, QGY-7703, and L02 cells, while the non-malignant L02 cells were less sensitive to the DNA-containing complex than to the chi-DOX complex, suggesting possible selectivity. Studies in tumor-bearing animals demonstrated that DNA/chi-DOX could efficiently deliver doxorubicin to the tumor and liver, implying that the DNA/chitosan nanocomplex may represent a novel drug carrier.