Biomedical subjects

G Ramachandra Reddy

Publications and source records attributed to G Ramachandra Reddy.

7 recordsLinked to original sources

PubMed2006

Vascular targeted nanoparticles for imaging and treatment of brain tumors.

PURPOSE: Development of new therapeutic drug delivery systems is an area of significant research interest. The ability to directly target a therapeutic agent to a tumor site would minimize systemic drug exposure, thus providing the potential for increasing the therapeutic index. EXPERIMENTAL DESIGN: Photodynamic therapy (PDT) involves the uptake of a sensitizer by the cancer cells followed by photoirradiation to activate the sensitizer. PDT using Photofrin has certain disadvantages that include prolonged cutaneous photosensitization. Delivery of nanoparticles encapsulated with photodynamic agent specifically to a tumor site could potentially overcome the drawbacks of systemic therapy. In this study, we have developed a multifunctional polymeric nanoparticle consisting of a surface-localized tumor vasculature targeting F3 peptide and encapsulated PDT and imaging agents. RESULTS: The nanoparticles specifically bound to the surface of MDA-435 cells in vitro and were internalized conferring photosensitivity to the cells. Significant magnetic resonance imaging contrast enhancement was achieved in i.c. rat 9L gliomas following i.v. nanoparticle administration. Serial magnetic resonance imaging was used for determination of pharmacokinetics and distribution of nanoparticles within the tumor. Treatment of glioma-bearing rats with targeted nanoparticles followed by PDT showed a significant improvement in survival rate when compared with animals who received PDT after administration of nontargeted nanoparticles or systemic Photofrin. CONCLUSIONS: This study reveals the versatility and efficacy of the multifunctional nanoparticle for the targeted detection and treatment of cancer.

Angiography↗

PubMed2006

Spectroscopic investigations of intermediates in the reaction of cytochrome P450(BM3)-F87G with surrogate oxygen atom donors.

Rapid mixing of substrate-free ferric cytochrome P450(BM3)-F87G with m-chloroperoxybenzoic acid (mCPBA) resulted in the sequential formation of two high-valent intermediates. The first was spectrally similar to compound I species reported previously for P450(CAM) and CYP 119 using mCPBA as an oxidant, and it featured a low intensity Soret absorption band characterized by shoulder at 370nm. This is the first direct observation of a P450 compound I intermediate in a type II P450 enzyme. The second intermediate, which was much more stable at pH values below 7.0, was characterized by an intense Soret absorption peak at 406nm, similar to that seen with P450(CAM) [T. Spolitak, J.H. Dawson, D.P. Ballou, J. Biol. Chem. 280 (2005) 20300-20309]. Double mixing experiments in which NADPH was added to the transient 406nm-absorbing intermediate resulted in rapid regeneration of the resting ferric state, with the flavins of the flavoprotein domain in their reduced state. EPR results were consistent with this stable intermediate species being a cytochrome c peroxidase compound ES-like species containing a protein-based radical, likely localized on a nearby Trp or Tyr residue in the active site. Iodosobenzene, peracetic acid, and sodium m-periodate also generated the intermediate at 406nm, but not the 370nm intermediate, indicating a probable kinetic barrier to accumulating compound I in reactions with these oxidants. The P450 ES intermediate has not been previously reported using iodosobenzene or m-periodate as the oxygen donor.

Chromatography, High Pressure Liquid↗

PubMed2006

Brain cancer diagnosis and therapy with nanoplatforms.

Treatment of brain cancer remains a challenge despite recent improvements in surgery and multimodal adjuvant therapy. Drug therapies of brain cancer have been particularly inefficient, due to the blood-brain barrier and the non-specificity of the potentially toxic drugs. The nanoparticle has emerged as a potential vector for brain delivery, able to overcome the problems of current strategies. Moreover, multi-functionality can be engineered into a single nanoplatform so that it can provide tumor-specific detection, treatment, and follow-up monitoring. Such multitasking is not possible with conventional technologies. This review describes recent advances in nanoparticle-based detection and therapy of brain cancer. The advantages of nanoparticle-based delivery and the types of nanoparticle systems under investigation are described, as well as their applications.

Blood-Brain Barrier↗

PubMed2003

A novel polyacrylamide magnetic nanoparticle contrast agent for molecular imaging using MRI.

A novel polyacrylamide superparamagnetic iron oxide nanoparticle platform is described which has been synthetically prepared such that multiple crystals of iron oxide are encapsulated within a single polyacrylamide matrix (PolyAcrylamide Magnetic [PAM] nanoparticles). This formulation provides for an extremely large T2 and T2* relaxivity of between 620 and 1140 sec(-1) mM(-1). Administration of PAM nanoparticles into rats bearing orthotopic 9L gliomas allowed quantitative pharmacokinetic analysis of the uptake of nanoparticles in the vasculature, brain, and glioma. Addition of polyethylene glycol of varying sizes (0.6, 2, and 10 kDa) to the surface of the PAM nanoparticles resulted in an increase in plasma half-life and affected tumor uptake and retention of the nanoparticles as quantified by changes in tissue contrast using MRI. The flexible formulation of these nanoparticles suggests that future modifications could be accomplished allowing for their use as a targeted molecular imaging contrast agent and/or therapeutic platform for multiple indications.

Acrylic Resins↗

PubMed2002

Structure of the 1,N(2)-propanodeoxyguanosine adduct in a three-base DNA hairpin loop derived from a palindrome in the Salmonella typhimurium hisD3052 gene.

The solution structure of the 1,N(2)-propanodeoxyguanosine (PdG) adduct was determined in a 3-base hairpin loop formed by d(CGCGGTXTCCGCG) (X = PdG). This sequence is contained within the Salmonella typhimurium hisD3052 gene, a hotspot for frameshift mutagenesis. PdG provides a structural model for the primary adduct induced in DNA by malondialdehyde, the 3-(2'-deoxy-beta-D-erythro-pentofuranosyl)pyrimido[1,2-a]-purin-10(3H)-one (M(1)G) lesion. The solution structure of the PdG-containing hairpin was refined by molecular dynamics calculations restrained by a combination of NMR-derived distances and dihedral angles, using a simulated annealing protocol. The structure of the PdG-modified hairpin consisted of a five-base-pair stem and a three-base loop consisting of T(6), X(7), and T(8). T(6) projected into the minor groove of the stem adjacent to G(4). The modified base X(7) stacked on top of the duplex stem and wedged between bases T(8) and C(9). The PdG moiety was oriented such that the imidazole proton was facing the minor groove of the stem and the exocyclic protons projected into the major groove. The structure of the adducted hairpin was compared with the structure of the corresponding unmodified oligodeoxynucleotide, and was found to be similar. There was a minor difference in the backbone angles of the G and PdG Hairpins at the phosphate linkage between G(5) and T(6) involving the G(5) epsilon angle and T(6) alpha and beta angles. The PdG-modified hairpin exhibited an increase in T(m) of approximately 2 degrees C compared to the unmodified hairpin. The structural and thermodynamic similarities suggested that PdG does not stabilize this hairpin and thus may not promote its extrusion in duplex DNA. The structural results are correlated with the results of site-specific mutagenesis experiments in the same sequence, which do not show evidence of frameshift mutations associated with hairpin loop formation. The geometry of this three-base loop is similar to that of other DNA hairpins containing three-base loops, and suggests a common motif for the folding of these loops.

Alcohol Oxidoreductases↗

PubMed2002

Structure of an oligodeoxynucleotide containing a 1,N(2)-propanodeoxyguanosine adduct positioned in a palindrome derived from the Salmonella typhimurium hisD3052 gene: Hoogsteen pairing at pH 5.2.

The structure of the 1,N(2)-Propanodeoxyguanosine (PdG) adduct was determined at pH 5.2 in the oligodeoxynucleotide duplex 5'-d(CGCGGTXTCCGCG)3'.5'-d(CGCGGACACCGCG)-3' (X = PdG). This sequence, referred to as the -TXT- sequence, is contained within the Salmonella typhimurium hisD3052 gene and contains a palindrome, representing a potential hotspot for frameshift mutagenesis. PdG provides a model for the primary adduct induced in DNA by malondialdehyde, the 3-(2'-deoxy-beta-D-erythro-pentofuranosyl)pyrimido[1,2-a]-purin-10(3H)-one (M(1)G) lesion. The solution structure was refined by molecular dynamics calculations restrained by a combination of NMR-derived distances and dihedral angles, using a simulated annealing protocol. PdG introduced a localized perturbation into the sequence at base pair X(7).C(20), which was pH-dependent. At neutral pH, conformational exchange resulted in spectral line broadening, and it was not possible to determine the structure. A stable structure was observed at pH 5.2 in which PdG rotated about the glycosyl bond into the syn conformation. This placed the exocyclic moiety into the major groove of the duplex. PdG formed a protonated Hoogsteen pair with nucleotide C(20) in the complementary strand. The pseudorotation of the deoxyribose at C(20) was altered to an approximately equal blend of C2'-endo and C3'-endo structures. However, these made little difference in the overall structure of the modified oligodeoxynucleotide. The structure was compared to that of PdG in the 5'-d(CGCXCGGCATG)-3'.5'-(CATGCCGCGCG)-3' sequence (the -CXC- sequence) at pH 5.8 [Singh, U. S., Moe, J. G., Reddy, G. R., Weisenseel, J. P., Marnett, L. J., and Stone, M. P. (1993) Chem. Res. Toxicol. 6, 825-836]. A sequence effect was observed. When PdG was placed into the -TXT- sequence at low pH, the structural perturbation was limited to the X(7).C(20) base pair. In contrast, when PdG was placed into the -CXC- sequence at low pH, both the modified base pair and its 3'-neighbor base pair were disrupted. The results are discussed in the context of differential outcomes for site-specific mutagenesis and replication bypass experiments when PdG was placed in the -TXT- and -CXC- sequences, respectively.

Alcohol Oxidoreductases↗

PubMedDate not supplied

Imaging of proteolytic activity using a conditional cell surface receptor.

Programmed cell death (apoptosis) is a ubiquitous means utilized by multicellular organisms for elimination of unwanted cells during development and homeostasis. Dysregulated apoptosis is implicated in an array of clinical disorders including cancer, autoimmune diseases, neurodegenerative disorders, and ischemia. During programmed cell death, a series of proteases, known as caspases, with different specificities play crucial roles in the apoptotic process. Caspase-3, a group II cysteine aspartate protease, recognizes and cleaves substrates harboring the amino acid sequence aspartic acid-glutamic acid-valine-aspartic acid (DEVD), and it plays an important role in the terminal phase of apoptosis. Here we report the development of a novel imaging platform for sensing the activation of cellular proteases. A recombinant chimeric protein was constructed, composed of a cell-surface-targeted single-chain antibody (sFv) fused to a Golgi retention signal. The DEVD tetrapeptide sequence was included between the single-chain antibody and the Golgi retention signal as a caspase-3 protease cleavage site. When expressed in cultured cells this fusion protein was localized to Golgi bodies and was not detected on the cell surface. Induction of apoptosis resulted in cleavage of the fusion protein releasing the single-chain antibody from the Golgi retention signal in a caspase-dependent manner. As a result, in cells undergoing apoptosis the single-chain antibody was visualized at the cell surface by immunofluorescence microscopy. The expression of sFv on the surface of cells in a protease-dependent manner provides a unique opportunity for real-time imaging through the use of targeted nanoparticles. This methodology may provide for a multimodal noninvasive real-time imaging of apoptosis and a new opportunity for high-throughput screening of cell-death-modulating therapeutic agents.

Animals↗