Biomedical subjects

Swadeshmukul Santra

Publications and source records attributed to Swadeshmukul Santra.

12 recordsLinked to original sources

PubMed2006

Nanoparticles for bioimaging.

The emergence of synthesis strategies for the fabrication of nanosized contrast agents is anticipated to lead to advancements in understanding biological processes at the molecular level in addition to progress in the development of diagnostic tools and innovative therapies. Imaging agents such as fluorescent dye-doped silica nanoparticles, quantum dots and gold nanoparticles have overcome many of the limitations of conventional contrast agents (organic dyes) such as poor photostability, low quantum yield, insufficient in vitro and in vivo stability, etc. Such particulates are now being developed for absorbance and emission in the near infrared region, which is expected to allow for real time and deep tissue imaging via optical routes. Other efforts to facilitate deep tissue imaging with pre-existing technologies have lead to the development of multimodal nanoparticles which are both optical and MRI active. The main focus of this article is to provide an overview of properties and design of contrast agents such as dye-doped silica nanoparticles, quantum dots and gold nanoparticles for non-invasive bioimaging.

Contrast Media↗

PubMed2006

Endovascular surgery for proximal posterior inferior cerebellar artery aneurysms: an analysis of Glasgow Outcome Score by Hunt-Hess grades.

OBJECTIVE: Proximal posterior inferior cerebellar artery (PICA) aneurysms represent a subset of posterior circulation aneurysms that can be routinely treated with either clipping or coiling. The literature contains limited numbers of patients with proximal PICA aneurysms treated with endovascular surgery. We report our experience with endovascular surgery of proximal PICA aneurysms with emphasis on patients with poor Hunt-Hess grades. METHODS: We reviewed 31 consecutive patients with proximal PICA aneurysms who were treated with endovascular surgery. The following data were analyzed: age, sex, size of aneurysm, Hunt-Hess grade at presentation, Fisher grade at presentation, angiographic result after embolization, complications, number of days hospitalized, duration of follow-up, angiographic follow-up results, and Glasgow Outcome Score at follow-up. RESULTS: Excellent angiographic occlusion was achieved in 30 of 31 (97%) patients. Clinical follow-up with Glasgow Outcome Score was performed on every patient an average of 10 months later. Twenty-one of 31 (68%) patients had good outcomes (Glasgow Outcome Score I or II) at follow-up. Of the patients who presented with a favorable clinical grade (Hunt-Hess 0-III), 13 of 15 (87%) had good outcomes at follow-up. Of the patients who presented with a poor clinical grade (Hunt-Hess Grade IV or higher), 8 of 16 (50%) had good outcomes at follow-up. CONCLUSION: This series demonstrates the safety and efficacy of endovascular surgery for proximal PICA aneurysms. Many patients with poor Hunt-Hess grades from ruptured PICA aneurysms ultimately had a good outcome. This could be secondary to early, aggressive treatment of hydrocephalus and the minimally invasive nature of the endovascular approach.

Adult↗

PubMed2006

Preoperative endovascular brain mapping for intraoperative volumetric image guidance: preliminary concept and feasibility in animal models.

OBJECT: The authors describe a novel concept for brain mapping in which an endovascular approach is used, and they demonstrate its feasibility in animal models. The purpose of endovascular brain mapping is to delineate clearly the nonfunctional brain parenchyma when a craniotomy is performed for resection. The nonfunctional brain will be stained with sharp visual margins, differentiating it from the functional, nonstained brain. The authors list four essential criteria for developing an ideal endovascular mapping agent, and they describe seven potential approaches for accomplishing a successful endovascular brain map. METHODS: Four Sprague-Dawley rats and one New Zealand white rabbit were used to determine initial feasibility of the procedure. The animals were anesthetized, and the internal carotid artery was catheterized. Four potential brain mapping agents were infused into the right hemisphere of the five animals. Afterward, the brains were removed and each was analyzed both grossly and histologically. Fluorescein and FD&C Green No. 3 provided good visual clarity and margins, but required blood-brain barrier (BBB) manipulation. Tantalum particles enabled avoidance of BBB manipulation, but provided inadequate visual clarity, probably because of their size. A Sudan black "cocktail" provided excellent clarity and margins despite remaining in the brain capillaries. CONCLUSIONS: This is a novel application of the endovascular approach, and has broad potential for clinical neurosurgical brain mapping. The animal models in this study establish the feasibility of the procedure. However, further study is required to demonstrate safety, minimize toxicity, investigate stain durability, and improve the characteristics of potential mapping agents. The authors are planning to conduct future studies for identification of mapping agents that do not require BBB manipulation or vascular occlusion.

Angiography, Digital Subtraction↗

PubMed2005

Rapid and effective labeling of brain tissue using TAT-conjugated CdS:Mn/ZnS quantum dots.

TAT (a cell penetrating peptide)-conjugated CdSratioMn/ZnS quantum dots (Qdots), intra-arterially delivered to a rat brain, rapidly (within a few minutes) labeled the brain tissue without manipulating the blood-brain-barrier (BBB). Qdot loading was sufficiently high that it allowed a gross fluorescent visualization of the whole rat brain using a low power hand-held UV lamp. Histological data clearly showed that TAT-conjugated Qdots migrated beyond the endothelial cell line and reached the brain parenchyma. Qdots without TAT did not label the brain tissue confirming the fact that TAT peptide was necessary to overcome the BBB. The present study clearly demonstrated the possibility of delivering a large amount of Qdot-based imaging agents to the brain tissue.

Animals↗

PubMed2005

Synthesis of water-dispersible fluorescent, radio-opaque, and paramagnetic CdS:Mn/ZnS quantum dots: a multifunctional probe for bioimaging.

Ultra-small (3.1 nm) multifunctional CdS:Mn/ZnS core-shell semiconductor quantum dots (Qdots), which possess fluorescent, radio-opacity, and paramagnetic properties, have been shown here. To demonstrate in vivo bioimaging capability, a rat was administered endovascularly with Qdots conjugated with a TAT peptide. The labeling efficacy of these Qdots was demonstrated on the basis of the histological analysis of the microtome sliced brain tissue, clearly showing that TAT-conjugated Qdots stained brain blood vessels.

Animals↗

PubMed2005

Finite element analysis of covered microstents.

Currently available neuroendovascular devices are inadequate for effective treatment of many wide-necked or fusiform intracranial aneurysms and intracranial carotid-cavernous fistulae (CCF). Placing a covered microstent across the intracranial aneurysm neck and CCF rent could restore normal vessel morphology by preventing blood flow into the aneurysm lumen or CCF rent. To fabricate covered microstents, our research group has developed highly flexible ultra thin (approximately 150 microm) silicone coverings and elastomerically captured them onto commercially available metal stents without stitching. Preliminary in vivo studies were conducted by placing these covered microstents in the common carotid artery of rabbits. The feasibility of using covered stents was demonstrated. However, the cover affected the deployment pressure and the stents failed occasionally during deployment due to tearing of the cover. Appropriate modeling of covered stents will assist in designing suitable coverings, and help to reduce the failure rate of covered microstents. The purpose of this study is to use the finite element method to determine the mechanical properties of the covered microstent and investigate the effects of the covering on the mechanical behavior of the covered microstent. Variations in the mechanical properties of the covered microstent such as deployment pressure, elastic recoil and longitudinal shortening due to change in thickness and material properties of the cover have been investigated. This work is also important for custom design of covered microstents such as adding cutout holes to save adjacent perforating arteries.

Blood Vessel Prosthesis↗

PubMed2005

Folate conjugated fluorescent silica nanoparticles for labeling neoplastic cells.

We describe a novel technique of using fluorescent silica nanoparticles (FSNPs) to detect over-expressed folate receptors, as typical for certain malignancies (metastatic adenocarcinoma, pituitary adenoma and others). Using Stöber's method with some modification, 135 nm size FSNPs were synthesized by a hydrolysis and co-condensation reaction of tetraethylorthosilicate (TEOS), fluorescein labeled (3-aminopropyl)triethoxysilane (APTS) and a water-dispersible silane reagent, (3-trihydroxysilyl)propyl methylphosphonate (THPMP) in the presence of ammonium hydroxide catalyst. Folic acid (folate) was covalently attached to the amine modified FSNPs by a carbodiimide coupling reaction. The characterization of folate-FSNPs was performed using a variety of spectroscopic (UV-VIS and fluorescence), microscopic (transmission electron microscopy, TEM) and light scattering techniques. Folate conjugated FSNPs were then targeted to human squamous cancer cells (SCC-9). Laser scanning confocal images successfully demonstrated the labeling of SCC-9 cells and the efficacy of FSNP based detection system.

Biomarkers, Tumor↗

PubMed2005

Syntheses and applications of Mn-doped II-VI semiconductor nanocrystals.

Luminescent Mn-doped II-VI semiconductor nanocrystals have been intensively investigated over the last ten years. Several semiconductor host materials such as ZnS, CdS, and ZnSe have been used for Mn-doped nanocrystals with different synthetic routes and surface passivation. Beyond studies of their fundamental properties including photoluminescence and size, these luminescent nanocrystals have now been tested for practical applications such as electroluminescent displays and biological labeling agents (biomarkers). Here, we first review ZnS:Mn, CdS:Mn/ZnS core/shell, and ZnSe:Mn nanocrystal systems in terms of their synthetic chemistries and photoluminescent properties. Second, based on ZnS:Mn and CdS:Mn/ZnS core/shell nanocrystals as electroluminescent components, direct current electroluminescent devices having a hybrid organic/inorganic multilayer structure are reviewed. Highly luminescent and photostable CdS:Mn/ZnS nanocrystals can further be used as the luminescent biomarkers and some preliminary results are also discussed here.

Crystallization↗

PubMed2005

Fluorescent nanoparticle probes for cancer imaging.

Optical imaging technique has strong potential for sensitive cancer diagnosis, particularly at the early stage of cancer development. This is a sensitive, non-invasive, non-ionizing (clinically safe) and relatively inexpensive technique. Cancer imaging with optical technique however greatly relies upon the use of sensitive and stable optical probes. Unlike the traditional organic fluorescent probes, fluorescent nanoparticle probes such as dye-doped nanoparticles and quantum dots (Qdots) are bright and photostable. Fluorescent nanoparticle probes are shown to be very effective for sensitive cancer imaging with greater success in the cellular level. However, cancer imaging in an in vivo setup has been recently realized. There are several challenges in developing fluorescent nanoparticle probes for in vivo cancer imaging applications. In this review, we will discuss various aspects of nanoparticle design, synthesis, surface functionalization for bioconjugation and cancer cell targeting. A brief overview of in vivo cancer imaging with Qdots will also be presented.

Diagnostic Imaging↗

PubMed2004

TAT conjugated, FITC doped silica nanoparticles for bioimaging applications.

Water-in-oil (w/o) microemulsion synthesis of 70 nm size monodisperse TAT (a cell penetrating peptide, CPP) conjugated, FITC (fluorescein isothiocyanate) doped silica nanoparticles (TAT-FSNPs) is reported; human lung adenocarcinoma (A549) cells (in vitro) and rat brain tissue (in vivo) were successfully labeled using TAT-FSNPs.

Animals↗

PubMed2004

Water-soluble silica-overcoated CdS:Mn/ZnS semiconductor quantum dots.

Highly luminescent and photostable CdS:Mn/ZnS core/shell quantum dots are not water soluble because of their hydrophobicity. To create water-soluble quantum dots by an appropriate surface functionalization, CdS:Mn/ZnS quantum dots synthesized in a water-in-oil (W/O) microemulsion system (reverse micelles) were consecutively overcoated with a very thin silica layer ( approximately 2.5 nm thick) within the same reverse micellar system. The water droplet serves as a nanosized reactor for the controlled hydrolysis and condensation of a silica precursor, tetraethyl orthosilicate (TEOS), using an ammonium hydroxide (NH4OH) catalyst. Structural characterizations with transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS) indicate that the silica-quantum dot nanocomposites consist of a layered structure. Owing to the amorphous, porous nature of a silica layer, the optical and photophysical properties of silica-overcoated CdS:Mn/ZnS quantum dots are found to remain close to those of uncoated counterparts.

Journal Article↗

PubMed2004

Luminescent nanoparticle probes for bioimaging.

Bioimaging with luminescent nanoparticle probes have recently attracted widespread interest in biology and medicine. In comparison with commonly used organic dyes, luminescent nanoparticles are better in terms of photostability and sensitivity. These optical features of nanoparticle probes are critical for real time tracking and monitoring of biological events in the cellular level, which may not be accomplished using regular fluorescent dyes. Nanoparticle probes are also shown highly suitable for immunoassay and other diagnostic and therapeutic applications. In this article, we describe a variety of optical nanoparticle probes such as quantum dots, metal nanoparticles, dye-doped nanoparticles etc. for bioimaging applications.

Fluorescent Dyes↗