Plasma Beads Research Articles

Plasma Bead Entrapped Liposomes as a Potential Drug Delivery System to Combat Fungal Infections.

Fibrin-based systems offer promises in drug and gene delivery as well as tissue engineering. We established earlier a fibrin-based plasma beads (PB) system as an efficient carrier of drugs and antigens. In the present work, attempts were made to further improve its therapeutic efficacy exploiting innovative ideas, including the use of plasma alginate composite matrices, proteolytic inhibitors, cross linkers, and dual entrapment in various liposomal formulations. In vitro efficacy of the different formulations was examined. Pharmacokinetics of the formulations encapsulating Amphotericin B (AmpB), an antifungal compound, were investigated in Swiss albino mice. While administration of the free AmpB led to its rapid elimination (<72 h), PB/liposome-PB systems were significantly effective in sustaining AmpB release in the circulation (>144 h) and its gradual accumulation in the vital organs, also compared to the liposomal formulations alone. Interestingly, the slow release of AmpB from PB was unusual compared to other small molecules in our earlier findings, suggesting strong interaction with plasma proteins. Molecular interaction studies of bovine serum albumin constituting approximately 60% of plasma with AmpB using isothermal titration calorimetry and in silico docking verify these interactions, explaining the slow release of AmpB entrapped in PB alone. The above findings suggest that PB/liposome-PB could be used as safe and effective delivery systems to combat fungal infections in humans.

Effective antigen delivery via dual entrapment in erythrocytes and autologous plasma beads

Fibrin-based polymeric systems have now emerged as efficient carriers of drugs, growth factors, genes, and cells. Earlier, we have reported fibrin-based plasma beads (PB), prepared from clotted whole plasma, as an efficient system for the controlled release of entrapped therapeutics. In the present study, we investigate the dual entrapment in erythrocytes and PB, as potential particulate antigen delivery system in rabbit and mice, with yeast invertase as the model antigen. Preparations used for immunisation include- invertase entrapped in erythrocytes, the same further entrapped in PB, and crosslinked with glutaraldehyde. While route of administration of the antigen only moderately affected the antibody titres, strategies slowing its release from PB increased the antibody titres remarkably, especially after a booster. Entrapment of erythrocytes entrapped antigen in the PB and further crosslinking with glutaraldehyde also resulted in significant alterations of IgG1/IgG2a ratio, indicating a shift towards humoral response. The elicited immune response was more marked in rabbits as compared to that in mice. Considering the well-known toxicity of the adjuvant, comparable antibody titres induced by the erythrocyte-plasma bead system was encouraging in the induction of humoral immunity.

Vaccine potential of plasma bead-based dual antigen delivery system against experimental murine candidiasis

The development of prophylactic anti-candidal vaccine comprising the Candida albicans cytosolic proteins (Cp) as antigen and plasma beads (PB) prepared from plasma as sustained delivery system, is described. The immune-prophylactic potential of various PBs-based dual antigen delivery systems, co-entrapping Cp pre-entrapped in PLGA microspheres were tested in the murine model. Induction of cell mediated immunity was measured by assaying DTH and NO production as well as in vitro proliferation of lymphocytes derived from the immunized animals. Expression of surface markers on APCs (CD80, CD86) and T-cells (CD4+, CD8+) was also evaluated. Humoral immune response was studied by measuring circulating anti-Cp antibodies and their subclasses. When the prophylactic efficacy of the vaccines was tested in mice challenged with virulent C. albicans, the PB-based formulation (PB-PLGA-Cp vaccine) was found to be most effective in the generation of desirable immune response, in terms of suppression of fungal load and facilitating the survival of the immunized animals.

Plasma beads loaded with Candida albicans cytosolic proteins impart protection against the fungal infection in BALB/c mice

The development of a prophylactic vaccine against systemic candidiasis, employing Candida albicans cytosolic proteins (Cp) as antigen and fibrin cross-linked plasma beads as an antigen bearing dual delivery system is described. Groups of mice were administered either with free Cp, or Cp entrapped in plasma beads, Cp entrapped in liposomes or liposome encapsulated Cp further entrapped in plasma beads. Humoral immunity was studied by measuring the anti-Cp antibody titers in the sera of the immunized animals. Induction of cell-mediated immunity was assessed by delayed type hypersensitivity (DTH), NO production, up-regulation of co-stimulatory molecules viz. CD80, CD86 on APCs on one hand and T-cells proliferation as well as induction of IFN-γ and IL-4 on the other. The efficacy of various vaccine formulations in protecting mice against a lethal challenge with C. albicans, was assessed by determining animal survival rate and fungal burden in the systemic circulation and vital organs. Among various Cp-based vaccines investigated, the preparation containing liposomized Cp entrapped in plasma beads imparted superior protection in the immunized mice as compared to other antigens delivery systems.

Vaccine potential of cytosolic proteins loaded fibrin microspheres of Cryptococcus neoformans in BALB/c mice

Cryptococcosis is a leading mycological cause of mortality among immunologically compromised individuals. In order to develop an effective vaccine against Cryptococcus neoformans, the cytosolic proteins (Cp) of the pathogen have been used as an antigen in combination with different formulations. In the present study, we have demonstrated that Cp encapsulated poly-lactide co-glycolide (PLGA) microsphere further co-encapsulated into the biocompatible fibrin cross-linked plasma beads (Fib-PLGA-Cp) mediated cytosolic delivery elicited strong immune response in the BALB/c mice. In contrast, other formulations of Cp failed to impart significant level of protection. The immune response, involved with Fib-PLGA-Cp protection, appear to interact with the target cells by both endocytosis as well as membrane fusion mode, thus helping in the activation of both CD4+ and CD8+ T-cells. Analysis of cytokine profiles in immunized animals revealed that the protective response was associated with the Th1/Th2 polarization in favor of type-1 cytokine [interferons (IFN)-γ and interleukin (IL)-2] cells. Furthermore, vaccination with Fib-PLGA-Cp elicited high immunoglobulin (Ig) Gl and IgG2a isotype response; successfully cleared fungal burden in vital organs and also increased the survival rate of immunized animals. Altogether the present study is a clear indicative of the possible use of fibrin microsphere-based targeted delivery of cytosolic proteins to induce protective immune responses against experimental murine cryptococcosis.

Beaded Plasma Clot: a Potent sustained-release, drug-delivery System

The aim of the study was to prepare a drug-entrapped, beaded form of blood plasma for possible sustained drug delivery. Blood plasma mixed with various drugs was enriched with CaCl2 and transferred in the form of small droplets on to a glass slide covered with parafilm. Clot formation was induced by incubation at 37 degrees C. Plasma-bead entrapped tetracycline, amphotericin B and daunorubicin were released gradually in vitro. Crosslinking of the beads with glutaraldehyde decreased the release rate of drugs remarkably. The plasma bead-entrapped cefotaxime administered subcutaneously in mice was released in a slow and sustained fashion and remained in circulation for a longer duration than the antibiotic administered in the free form. The plasma beads have potential for the sustained delivery of drugs in vivo, since their preparation does not require additional thrombin or other proteins and can be readily accomplished by using autologous plasma, thereby minimizing the risk of immunological complications.

Observations of the long distance exploding wire restrike mechanism

An exploding wire restrike mechanism is applied to create plasma paths up to 9 m in length. The mechanism uses enameled copper wires in a 5 to 10 kV/m region of average electric field (AEF). This relatively low AEF restrike mechanism appears to be linked to the formation of plasma beads along the wire’s length. Voltage traces, measurement of relative emitted light intensity and photographs are presented at AEFs below, inside and above the identified restrike region.

Fabrication of pre-determined shape of bone segment with collagen-hydroxyapatite scaffold and autogenous platelet-rich plasma

Reconstruction of large segment of bony defects is frequently needed in hand surgery. Autogenous bone grafting is considered the standard in management of these bony defects but has limited source of graft material. Collagen and hydroxyapatite have been used as bone-filling materials and are known to serve as the osteoconductive scaffold for bone regeneration. On the other hand, platelet-rich plasma is a kind of natural source of growth factors, and has been used successfully in bone regeneration and improving wound healing. This study was designed to evaluate the effectiveness of using biohybrids of platelet-rich plasma and collagen-hydroxyapatite beads for fabricating of protrusive bone in a rabbit animal model. Biomaterial beads comprised of particulate hydroxyapatite dispersed in fibrous collagen (type I) matrices were prepared and filled in the ringed polytetrafluoroethylene (PTFE) artificial vascular graft (3 cm long, 1 cm in diameter). New Zealand White rabbits were each implanted with two cylindrical PTFE artificial vascular graft over both iliac crests (n = 16). A 2 x 0.5 cm opening was created at the side of each PTFE chamber to allow the content of chamber in contact with the bone marrow of the ileum. The chambers were empty (groups A and D), filled with type I collagen/hydroxyapatite beads (groups B and C). In groups C and D, autologous platelet rich plasma (PRP) was given by transcutaneous injection method into the chambers every week. After 12 weeks, the animals were sacrificed and the chambers were harvested for radiological and histological analysis. In plain radiographs, the group C chambers had significantly higher bone tissue engineered (average calcified density 0.95, average calcified area 61.83%) compared with other groups (P < 0.001). In histological examination, there was a creeping substitution of the implant by the in-growth of fibrovascular tissue in group C. Abundant fibrovascular networks positioned interstitially between these biomaterial beads in all parts of chamber. Degradation of these beads and newly formed capillaries and osteoids around the degraded matrixes are shown. The continually calcification in the matrixes or degraded matrixes is evidenced by the strong green fluorescence observed under the confocal microscope. In group B, looser architecture without evidence of tissue in-growth was shown. In the scaffold absent groups (A and D), there was only fibrous tissue shown within the chamber. In this study, we have demonstrated a feasible approach to fabricate an osseous tissue that meets clinical need. Using the type I collagen/ hydroxyapatite gel beads matrixes and intermittent injection of autologous platelet-rich-plasma, specific 3D osseous tissues with fibrovascular network structure from pre-exist bony margin were successfully created in an in vivo animal model.

Laser-induced discharge in a rod-plane electrode in the presence of a negative dc electric field

Discharge induction experiments were performed between a plate and a rod on a plate electrode configuration with a gap length of 1 m using a high-power CO2 laser and a dc voltage generator. The electrodes are parallel planes. Each plate electrode consists of a central flat part having a diameter of 3 m with a circular edge on a cross section. The length of the rod is 10 cm. A chain of plasma beads of length 10 cm was created on the tip of the rod by the CO2 laser and used for artificial triggering of negative high-voltage sparkover. The behavior of streamer, leader, and return stroke was observed by an image converter camera. It was found that a positive upward traveling leader can be triggered from the tip of the rod on the lower plane to the upper plane by the chain of plasma beads created by the CO2 laser. This apparatus is useful for study for realization of laser-induced lightning. © 2000 Scripta Technica, Electr Eng Jpn, 132(4): 19–27, 2000

Formation Processes of Laser Induced Discharge Path.

It is well known that plasma beads are produced in the atmosphere by a focused high-power laser beam. The characteristics of propagation of a CO2 laser beam in the atmosphere including the plasma beads produced by focusing the laser beam were investigated. The optical air-breakdown mechanism was treated by empirical relations instead of taking inverse bremsstrahlung into considerations. A simple equation was newly proposed here to describe processes of growing of plasma beads. The simulated results on the density of plasma beads were qualitatively in agreement with experimental results. The model consisting of these procedures has a possibility to predict the density of plasma beads which are produced in the atmosphere by a CO2 laser owing to ignition of atmospheric aerosols.

Fundamental Experiments on Laser Triggered Lightning. Plasma Generation under Winter Thunderstorms.

It is a crucial issue to make an intense plasma channel in the atmosphere for laser triggered lightning. The laser characteristics of laser propagation and plasma generation have been studied under various weather conditions. The line density of plasma channel in snowy weather is less than that in fine weather due to the laser energy attenuation and the decrease of aerosols, the cores of plasma beads, by snow. To initiate a leader at the top of lightning tower, the line density of plasma channel is needed to be over one hundred per meter. Some remedies to overcome this effects will be discussed.

Study on Laser Triggered Discharge Using a CO2 Laser.

We are preparing a laser triggered lightning method for the winter thunderstorm. Using a - 150-J electron beam excited CO2 laser, we obtained a laser plasma channel consisting of many plasma beads made of ionized aerosols in the atmosphere. The laser plasma channel initiates an electrical streamer and propagates a leader. We discuss experimental results on the critical conditions for initiating streamer from a laser plasma channel and for leader propagation through a laser plasma channel.

Laser Triggered Lightning.

Electrical discharge guided by a 100J/2GW pulse CO2 laser is reviewed. A long air break-down plasma channel is produced by using a Multi-Active CHannel (MACH) focusing mirror which has two focal lengthes. The plasma channel has been used to guide electrical discharge over a distance of 6m in laboratory air at an applied potential of-1.2MV. A successive plasma channel produced by the laser is more effective for discharge guiding than the chains of break plasma beads. A stepped leader was obserbed with a streak camera for laser guided discharge. The mean propagation velocity of the stepped leader was 105-106m/s.

Effects of Gamma Emission on Laser Ionized Plasma Channels for Inertial Confinement Fusion Reactors

Experiments have been performed to measure the effect of /sup 137//sub 55/Cs gamma emission on the length and distribution of long chains of CO/sub 2/ laser-induced plasma beads in atmospheric pressure air. Schlieren photography data show that negative ions produced by the /sup 137//sub 55/Cs source result in a shift of the breakdown plasma to lower CO/sub 2/ laser intensity regions. No significant change in the total plasma length or uniformity has been observed. These experiments are relevant to the role of wall activation in fusion reactors using electron or light ion beams injected through plasma channels.