Safety and toxicity issues associated with lead-based traditional herbo-metallic preparations

ETHNOPHARMACOLOGICAL RELEVANCE

Herbal and herbo-mineral preparations are being traditionally used in Indian medicines. The herbo-mineral preparations have several benefits that have been instrumental in their widespread use in treatment of different disorders by traditional medicinal practitioners. These include better stability, lower dosage, ease of storability and sustained availability. Naga bhasma (lead sulphide ash), a traditional Indian herbo-mineral medication prepared using lead and several herbal ingredients, has been used as an oral medicine in India for many years for the treatment of diabetes, spleen enlargement, diarrhoea and various skin diseases. The elaborate preparation protocol involved in the traditional medicines is believed to modify the toxic nature of the precursor (metal) and adds therapeutic value. But modern scientists claim that these preparations are toxic to health as they contain large amount of metal. Many factors such as preparation based factors, chemical nature based factors, vehicle used, therapy associated factors, pharmacological factors, etc, determine whether the traditional medicines are toxic or not. This review focuses on the safety and critical issues associated with Naga bhasma-a lead based ayurvedic medicine.

MATERIALS AND METHODS

The detailed review of literature about Naga bhasma apart from other lead based formulations are carried out by utilizing the resources including, classical Indian text books, databases such as Pub med, Scopus, Science direct and few other web sources.

RESULTS

Though metallic lead is known to be toxic to the biological system, no compelling evidence has been put forth to suggest any toxic manifestations of Naga bhasma. The elemental characterization of preparations containing Naga bhasma has shown extremely high levels of lead content and various parameters must be taken into consideration in deciding the safety and critical issues present in traditional medicines. As there are no molecular targets available for most of the traditional medicine, it is difficult to assure the safety in using this traditional preparation. Highly intensive research encompassing physico-chemical, engineering as well as biological aspects need to be carried out to understand the applicability of such preparations in a modern context.

CONCLUSION

As there are no molecular targets available for most of the traditional medicine, it is difficult to assure the safety in using this traditional preparation. Highly intensive research encompassing physico-chemical, engineering as well as biological aspects need to be carried out to understand the applicability of such preparations in a modern context.

Self-assembling peptide nanofibrous scaffolds for tissue engineering: novel approaches and strategies for effective functional regeneration

Tissue engineering requires an ideal scaffold that will aid in the regeneration of the damaged tissues both structurally and functionally. Conventionally, polymeric nanofibrous scaffolds have been extensively used due to their structural similarity to the native extracellular matrix. Thus far, top-down approaches like electrospinning and phase separation have been predominantly used for the nanofiber fabrication. Recently, self-assembling peptide nanofibers (SAPNF) have been identified as promising scaffolds for tissue engineering applications. Molecular self-assembly of peptides, which is a bottom-up approach has laid foundations for the development of such novel scaffolds. Designer self-assembling peptides provide functional support as well as bio-recognition due to the presence of bioactive motifs embedded in them. However, there are certain limitations to both electrospun and SAPNF scaffolds in terms of synthesis, cues presented to the biological system and applications. Design of composite, hybrid scaffolds by super-positioning possible cues may result in effective functional tissue regeneration at multiple levels.

Flavonoid-metal ion complexes: a novel class of therapeutic agents

Flavonoids are among the most investigated phytochemicals due to their pharmacological and therapeutic activities. Their ability to chelate with metal ions has resulted in the emergence of a new category of molecules with a broader spectrum of pharmacological activities. However, the biological significance of these flavonoid-metal ion complexes is yet to be completely explored. Moreover, no concerted efforts have been made to elucidate their molecular targets and mechanisms of action. This review attempts to provide a snapshot of the various biological activities reported for flavonoid-metal ion complexes and their potential as therapeutic agents. Understanding the mechanism of action and the influence of structure will provide a strong basis to design novel flavonoid-metal ion complexes of therapeutic significance.

Polymeric scaffold aided stem cell therapeutics for cardiac muscle repair and regeneration

The constantly expanding repository of novel polymers and stem cells has opened up new vistas in the field of cardiac tissue engineering. Successful regeneration of the complex cardiac tissue mainly centres on the appropriate scaffold material with topographical features that mimic the native environment. The integration of stem cells on these scaffolds is expected to enhance the regeneration potential. This review elaborates on the interplay of these vital factors in achieving the functional cardiac tissue. The recent advances in polymers, nanocomposites, and stem cells from different sources are highlighted. Special emphasis is laid on the clinical trials involving stem cells and the state-of-the-art materials to obtain a balanced perspective on the translational potential of this strategy.

Fabrication of lactate biosensor based on lactate dehydrogenase immobilized on cerium oxide nanoparticles

An electrochemical biosensor was developed to determine lactate that plays an important role in clinical diagnosis, fermentation and food quality analysis. Abnormal concentration of lactate has been related to diseases such as hypoxia, acute heart disorders, lactic acidosis, muscle fatigue and meningitis. Also, lactate concentration in blood helps to evaluate the athletic performance in sports. The main aim of the work is to fabricate NADH/LDH/Nano-CeO2/GCE bio-electrode for sensing lactate in human blood samples. Toward this, CeO2 nanoparticles were synthesized by a hydroxide mediated approach using cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and NaOH as precursors. X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FE-SEM) studies were carried out to determine the structural and morphological characteristics of CeO2 nanoparticles. XRD pattern indicated the formation of highly crystalline CeO2 nanoparticles with face centered cubic structure. The FE-SEM studies revealed the formation of nanospherical particles of size 29.73±2.59 nm. The working electrode was fabricated by immobilizing nicotinamide adenine dinucleotide (NADH) and lactate dehydrogenase (LDH) on GCE surface with CeO2 nanoparticles as an interface. Electrochemical studies were carried out through cyclic voltammetry using a three electrode system with NADH/LDH/NanoCeO2/GCE as a working electrode, Ag/AgCl saturated with 0.1M KCl as a reference electrode and Pt wire as a counter electrode. From the amperometric study, the linearity was found to be in the range of 0.2-2 mM with the response time of less than 4s.

Mechanistic insights of curcumin interactions with the core-recognition motif of β-amyloid peptide

Alzheimer's disease is a neurodegenerative disease affecting millions of people worldwide. The proteolytic cleavage of amyloid precursor protein forms amyloid beta peptide (Aβ(1-42)), which aggregates to form senile plaques. The KLVFF motif present in Aβ(1-42) is essential for aggregation. Curcumin, a prinicipal curcuminoid present in turmeric, shows therapeutic activity against Alzheimer's disease. However, the nature of interaction between the A(β1-42) peptide and curcumin remains unexplored. Studies on the interaction of the core-recognition motif KLVFF with curcumin can be extrapolated to decipher the interactions between A(β1-42) and curcumin. Our data show that curcumin and KLVFF interact strongly through hydrophobic forces and are stabilized by hydrogen bonding. The hydrophobic interactions were confirmed from the positive shift in the phase transition temperature. Fluorescence quenching studies demonstrate a static quenching mechanism. FTIR data confirm the β sheet breaking ability of curcumin, which is also substantiated by cell culture studies.

Synthesis, characterization and biocompatibility evaluation of iron oxide incorporated magnetic mesoporous silica

On the basis of a thermal process, a facile, low cost, one-step approach for preparing iron oxide (Fe(2)O(3)) incorporated ordered magnetic mesoporous silica nanocomposites by a co-operative self-assembly approach is presented. Various mesostructured silica materials incorporated with different amounts of iron oxide (nSi/nFe = 1/1, 1/0.5, 1/0.25 and 1/0.123) at various pH (<1, 3, 5 and 7) were synthesized and characterized by electron microscopy and X-ray diffractometry. Further, the surface area and magnetic properties were evaluated using N(2)-sorption analyses, and a superconducting quantum interference device interfaced with a vibrating sample magnetometer (SQUID-VSM) respectively. The transmission electron micrographs and nitrogen sorption analysis indicated that most of the Fe(2)O(3) domains of several nanometers were embedded in the silica walls, rather than dispersed in the mesopores. The incorporation of iron oxide into the mesopores without compromising the structural and textural properties was achieved at pH < 1. These structures have great potential in diagnostics and therapeutics. However, the acceptance of this material by the biological host is a critical issue for such biomedical applications. In this study, we have also evaluated the in vivo biocompatibility of these magnetic mesoporous materials in a rat model. The histopathological results show that this magnetic material can be classified as a level 2 biomaterial that can be safely used for short term applications such as MRI imaging, hyperthermia, targeted drug delivery, etc.

Development of poly(butylene succinate) microspheres for delivery of levodopa in the treatment of Parkinson's disease

Parkinson's is a major neurodegenerative disorder that occurs due to loss of dopaminergic neurons in basal ganglia. Conventional therapy includes surgery that involves lot of risk and administration of levodopa which is accompanied by poor bioavailability, short half-life, and side effects. In the present study, poly(butylene succinate) (PBSu) microspheres-based drug delivery system to improve the bioavailability of the drug levodopa was evaluated for the first time. Biodegradable porous and smooth PBSu microspheres were prepared by double emulsion solvent evaporation technique (W/O/W) and the effect of solvent and surfactant was studied. The maximum encapsulation efficiency achieved was 53.93% and 62.28% for porous and smooth microspheres, respectively. In vitro drug release was studied in phosphate buffered saline and simulated CSF buffer of pH 7.4. Initially a burst effect followed by sustained release of drug was obtained for about 32 h and 159 h for porous and smooth microspheres, respectively. The release rate was higher in simulated CSF when compared with PBS, due to higher concentration of sodium ions and cations in simulated CSF.

Axially aligned electrically conducting biodegradable nanofibers for neural regeneration

In this study, electrically conducting axially aligned nanofibers have developed to provide both electrical and structural cues. Poly(lactide-co-glycolide) (PLGA) with poly(3-hexylthiophene) (PHT) was electrospun into 2D random (196 ± 98 nm) and 3D axially aligned nanofibers (200 ± 80 nm). Electrospun random and aligned PLGA-PHT fibers were characterized for surface morphology, mechanical property, porosity, degradability, and electrical conductivity. The pore size of random PLGA-PHT nanofibers (6.0 ± 3.3 μm) were significantly higher than the aligned (1.9 ± 0.4 μm) (P < 0.05) and the Young's modulus of aligned scaffold was significantly lower than the random. Aligned nanofibers showed significantly lesser degradation rate and higher electrical conductivity (0.1 × 10(-5) S/cm) than random nanofibers (P < 0.05). Results of in vitro cell studies indicate that aligned PLGA-PHT nanofibers have a significant influence on the adhesion and proliferation of Schwann cells and could be potentially used as scaffold for neural regeneration.

Axially aligned electrically conducting biodegradable nanofibers for neural regeneration

In this study, electrically conducting axially aligned nanofibers have developed to provide both electrical and structural cues. Poly(lactide-co-glycolide) (PLGA) with poly(3-hexylthiophene) (PHT) was electrospun into 2D random (196 ± 98 nm) and 3D axially aligned nanofibers (200 ± 80 nm). Electrospun random and aligned PLGA-PHT fibers were characterized for surface morphology, mechanical property, porosity, degradability, and electrical conductivity. The pore size of random PLGA-PHT nanofibers (6.0 ± 3.3 μm) were significantly higher than the aligned (1.9 ± 0.4 μm) (P < 0.05) and the Young's modulus of aligned scaffold was significantly lower than the random. Aligned nanofibers showed significantly lesser degradation rate and higher electrical conductivity (0.1 × 10(-5) S/cm) than random nanofibers (P < 0.05). Results of in vitro cell studies indicate that aligned PLGA-PHT nanofibers have a significant influence on the adhesion and proliferation of Schwann cells and could be potentially used as scaffold for neural regeneration.

Scientific validation of the different purification steps involved in the preparation of an Indian Ayurvedic medicine, Lauha bhasma

ETHNOPHARMACOLOGICAL RELEVANCE

Lauha bhasma (iron ash) is one of the iron-based herbo-metallic preparations used in Ayurvedic medicine for treating various ailments due to iron deficiency.

MATERIALS AND METHODS

The preparation of Lauha bhasma (iron ash) requires normal purification (heat treatment in vegetable and animal products), special purification (treatment with herbal constituents) and calcination steps aimed at converting the raw material to a suitable therapeutic form. In this study, we have systematically and scientifically evaluated through a series of qualitative tests and modern analytical tools the importance of the treating media.

RESULTS

Our data demonstrates that these steps are necessary to remove the grease and scales in the raw material. While heating, microcracks appeared on the surface of the iron, which improved the reactivity with the herbal constituents in addition to incorporating nanostructured features. Further, the use of plant products facilitated the removal of Fe³⁺ present in the raw material by forming soluble complexes. The Fe²⁺ present in the raw materials also forms an insoluble complex with the herbal constituents in the presence of UV radiation.

CONCLUSIONS

In conclusion, our data summarily suggest that the purification steps involved in the preparation of Lauha bhasma (iron ash) are critical.

Investigation on the stability of saquinavir loaded liposomes: implication on stealth, release characteristics and cytotoxicity

Although anti-retroviral therapy is the most efficient disease management strategy for HIV-AIDS, its applications are limited by several factors including the low bioavailability and first pass metabolism of the drugs. Nanocarriers such as liposomes have been developed to circumvent some of these problems. We report here preparation of novel liposome formulations for efficient delivery of anti-retroviral drugs to mammalian cells in culture. The liposomes were prepared and surface was modified using poly (ethylene glycol). Encapsulation efficiency of the anti-retroviral drug saquinavir was found to be approximately 33% and also exhibited sustained release of the drug. Although PEGylated liposomes were more stable in protein-supplemented media, had better colloidal stability and exhibited lesser sonochemical stability due to lower cavitation threshold. The cell viability studies using Jurkat T-cells revealed that the PEGylated liposomes loaded with saquinavir were less cytotoxic as compared to the non-PEGylated liposomes or free drug confirming the potential of the liposomes as a sustained drug-release system. The drug delivery potential of the liposomes loaded with Alexa flour 647 was evaluated using Jurkat T-cells and flow cytometry showing uptake upto 74%. Collectively, our data demonstrate efficient targeting of mammalian cells using novel liposome formulations with insignificant levels of cytotoxicity.

Tissue engineering interventions for esophageal disorders--promises and challenges

The diseases of the esophagus include congenital defects like atresia, tracheoesophageal fistula as well as others such as gastro-esophageal reflux disease (GERD), Barrett's esophagus, carcinoma and strictures. All esophageal disorders require surgical intervention and reconstruction with appropriate substitutes. Primary anastomosis is used to treat most cases but treatment of long gap atresia still remains a clinical challenge. Autologous graft therapies using tissues from colon, and small and large intestine or gastric transplantations have been attempted but have constraints like leakage, infection and stenosis at the implanted site, which leads to severe morbidity and mortality. An alternative for autologous grafts are allogenic and xenogenic grafts, which have better availability but disease transmission and immunogenicity limit their applications. Use of biodegradable and biocompatible scaffolds to engineer the esophagus promises to be an effective regenerative strategy for treatment of esophageal disorders. Nanotopography of the fibrous scaffolds mimics the natural extracellular matrix (ECM) of the tissue and incorporation of chemical cues and tailoring mechanical properties provide the right microenvironment for co-culture of different cell types. Scaffolds cultured with esophageal cells (epithelial cells, fibroblast and smooth muscle cells) might show enhancement of the biofunctionality in vivo. This review attempts to address the various strategies and challenges involved in successful tissue engineering of the esophagus.

Role of biomaterials, therapeutic molecules and cells for hepatic tissue engineering

Current liver transplantation strategies face severe shortcomings owing to scarcity of donors, immunogenicity, prohibitive costs and poor survival rates. Due to the lengthy list of patients requiring transplant, high mortality rates are observed during the endless waiting period. Tissue engineering could be an alternative strategy to regenerate the damaged liver and improve the survival and quality of life of the patient. The development of an ideal scaffold for liver tissue engineering depends on the nature of the scaffold, its architecture and the presence of growth factors and recognition motifs. Biomimetic scaffolds can simulate the native extracellular matrix for the culture of hepatocytes to enable them to exhibit their functionality both in vitro and in vivo. This review highlights the physiology and pathophysiology of liver, the current treatment strategies, use of various scaffolds, incorporation of adhesion motifs, growth factors and stem cells that can stabilize and maintain hepatocyte cultures for a long period.

Investigations on membrane perturbation by chrysin and its copper complex using self-assembled lipid bilayers

The mechanism of membrane interactions of most of the flavonoids in the presence of transition-metal ions is not well-understood. To understand this phenomenon, the present work aims to synthesize a chrysin-copper complex at room temperature and investigate its influence on the electrical characteristics of planar lipid bilayers. The chrysin-copper complex was characterized by various spectroscopic techniques and was found to have a metal/ligand ratio of 1:2 and of cationic nature. Its ability to inhibit 1,1'-diphenyl-2-picrylhydrazyl (DPPH) radicals was not significant at alkaline pH because of the involvement of the 5-hydroxy group in coordination with the copper ion compared to its parent flavonoid, chrysin (p < 0.05). The addition of different concentrations (20-100 μM) of chrysin and the chrysin-copper complex to lipid bilayers decreases the resistance, indicating a strong surface interaction and partial insertion into the bilayer near the lipid-water interface. The dose-dependent reduction in resistance as a result of the chrysin-copper complex is more pronounced in comparison to chrysin, implying that the bulkier and charged chrysin-copper complex displays greater ability to distort the lipid bilayer architecture. These conclusions were further confirmed by curcumin-loaded liposome permeabilization studies, where both chrysin and its Cu(II) complex increased the fluidity in a dose-dependent manner. However, the extent of fluidization by the chrysin-copper complex was nearly twice that of chrysin alone (p < 0.05). The implications of these surface interactions of chrysin and its copper complex on cell membranes were studied using a hypotonic hemolysis assay. Our results demonstrate that, at low concentrations (20 μM), the chrysin-copper complex exhibited twice the protection against hypotonic stress-induced membrane disruption when compared to chrysin. However, this stabilizing effect gradually decreased and became comparable to chrysin at higher concentrations. This biphasic behavior of the chrysin-copper complex could further be explored for therapeutic applications.

A novel nanostructured iron oxide-gold bioelectrode for hydrogen peroxide sensing

Fe(3)O(4) nanoparticles covalently linked to a gold electrode have been used for immobilizing catalase (CAT) enzyme to sense the presence of various concentrations of H(2)O(2). These nanoparticles ranging from 20 to 30 nm were synthesized by thermal co-precipitation of ferric and ferrous chlorides. SEM and XRD have been used for morphological and structural characterization of Fe(3)O(4) nanoparticles. CAT enzyme was linked covalently to the surface of iron oxide using carbodiimide in phosphate buffer (pH 7.4) at 4 °C. The enzyme-iron oxide link was confirmed by FT-IR spectroscopy. Sensing studies carried out using cyclic voltammetry showed a linear response of the CAT/nano Fe(3)O(4)/Au bioelectrode towards H(2)O(2) between 1.5 and 13.5 µM with a very sharp response time of 2 s.

Biodegradable Poly[bis(ethyl alanato)phosphazene] - Poly(lactide-co-glycolide) Blends: Miscibility and Osteocompatibility Evaluations

We have previously demonstrated that blending biodegradable glycine co-substituted polyphosphazenes with poly(lactide-co-glycolide) (PLAGA) results in novel biomaterials with versatile properties. The study showed that the degradation rate of polyphosphazene/PLAGA blends can be effectively controlled by varying the blend composition while at the same time the degradation products of polyphosphazenes effectively neutralized the acidic degradation products of PLAGA. In the present study, novel blends of hydrophobic, biodegradable polyphosphazene, poly[bis(ethyl alanato) phosphazene] (PNEA) and PLAGA (LA: GA; 85:15) were developed as candidates for bone tissue engineering applications. Two different blend compositions were developed by blending PNEA and PLAGA having weight ratios of 25:75 (Blend-1) and 50:50 (Blend-2) by the mutual solvent technique using dichloromethane as the solvent. The miscibility of the blends was determined using differential scanning calorimetry (DSC), fourier transform-infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). Surface analysis of the blends by SEM revealed a smooth uniform surface for Blend-1, whereas Blend-2 showed evidence of phase separation. PNEA is not completely miscible with PLAGA, as evidenced from DSC and FT-IR measurements. The osteocompatibilities of Blend-1 and Blend-2 were compared to those of parent polymers by following the adhesion and proliferation of primary rat osteoblast cells on two dimensional (2-D) polymer and blend films over a 21 day period in culture. Blend films showed significantly higher cell numbers on the surface compared to PLAGA and PNEA films.

Development of Novel Biodegradable Amino Acid Ester Based Polyphosphazene– Hydroxyapatite Composites for Bone Tissue Engineering

Hydroxyapatite formed from low temperature setting calcium phosphate cements (CPC) are currently been used for various orthopaedic applications. CPCs are attractive candidates for the development of scaffolds for bone tissue engineering, since they are moldable, resorbable, set at physiological temperature without the use of toxic chemicals, and can be processed in an operating room setting. However they may have mechanical disadvantages which seriously limit them to non-load bearing orthopaedic applications. The aim of the present study was to develop composites from polyphosphazenes and calcium deficient hydroxyapatite precursors to form poorly crystalline hydroxyapatite-polymer composites. Composites were formed from calcium deficient hydroxyapatite precursors (Ca/P – 1.5, 1.6) and biodegradable polyphosphazenes, poly[bis(ethyl alanato)phosphazene] (PNEA) and poly[(50%ethyl alanato) (50%methyl phenoxy)phosphazene] (PNEA50mPh50) at physiological temperature. The results demonstrated that poorly crystalline hydroxyapatite that resembled the mineral component of bone was formed in the presence of biodegradable polyphosphazenes. The surface morphology of all the four composites was identical with a porous microstructure. The composites supported the adhesion and proliferation of osteoblast like MC3T3-E1 cells making them potential candidates for bone tissue engineering.

Fabrication and characterization of chitosan-gelatin blend nanofibers for skin tissue engineering

Tissue engineering scaffolds produced by electrospinning feature a structural similarity to the natural extracellular matrix. Polymer blending is one of the effective methods to provide new and desirable biocomposites for tissue engineering applications. In this study chitosan was blended with gelatin and the effect of processing parameters of electrospinning and the solution properties of the polymer on the morphology of the fibers obtained were investigated. The morphology of the electrospun chitosan, gelatin and the chitosan-gelatin blend were characterized using a scanning electron microscope (SEM). The miscibility of the blend was determined using a SEM, and differential scanning calorimetry (DSC) Fourier transform Infrared spectrometer (FTIR). Further the tensile properties of the blend nanofibers were studied and compared with chitosan and gelatin fibers. In this study we have been able to electrospin defect-free chitosan, gelatin and chitosan-gelatin blend nanofibers with smooth morphology and diameter ranging from 120 to 200 nm, 100 to 150 nm, and 120-220 nm, respectively by optimizing the process and solution parameters. Chitosan and gelatin formed completely miscible blends as evidenced from DSC and FTIR measurements. The tensile strength of the chitosan-gelatin blend nanofibers (37.91 +/- 4.42 MPa) was significantly higher than the gelatin nanofibers (7.23 +/- 1.15 MPa) (p < 0.05) and comparable with that of normal human skin. Thus the novel chitosan-gelatin blend nanofiber system has potential application in skin regeneration.

Development of a liposomal nanodelivery system for nevirapine

BACKGROUND

The treatment of AIDS remains a serious challenge owing to high genetic variation of Human Immunodeficiency Virus type 1 (HIV-1). The use of different antiretroviral drugs (ARV) is significantly limited by severe side-effects that further compromise the quality of life of the AIDS patient. In the present study, we have evaluated a liposome system for the delivery of nevirapine, a hydrophobic non-nucleoside reverse transcriptase inhibitor. Liposomes were prepared from egg phospholipids using thin film hydration. The parameters of the process were optimized to obtain spherical liposomes below 200 nm with a narrow polydispersity. The encapsulation efficiency of the liposomes was optimized at different ratios of egg phospholipid to cholesterol as well as drug to total lipid. The data demonstrate that encapsulation efficiency of 78.14% and 76.25% were obtained at egg phospholipid to cholesterol ratio of 9:1 and drug to lipid ratio of 1:5, respectively. We further observed that the size of the liposomes and the encapsulation efficiency of the drug increased concomitantly with the increasing ratio of drug and lipid and that maximum stability was observed at the physiological pH. Thermal analysis of the drug encapsulated liposomes indicated the formation of a homogenous drug-lipid system. The magnitude of drug release from the liposomes was examined under different experimental conditions including in phosphate buffered saline (PBS), Dulbecco's Modified Eagle's Medium (DMEM) supplemented with 10% fetal bovine serum or in the presence of an external stimulus such as low frequency ultrasound. Within the first 20 minutes 40, 60 and 100% of the drug was released when placed in PBS, DMEM or when ultrasound was applied, respectively. We propose that nevirapine-loaded liposomal formulations reported here could improve targeted delivery of the anti-retroviral drugs to select compartments and cells and alleviate systemic toxic side effects as a consequence.

Mechanical properties and osteocompatibility of novel biodegradable alanine based polyphosphazenes: Side group effects

The versatility of polymers for tissue regeneration lies in the feasibility to modulate the physical and biological properties by varying the side groups grafted to the polymers. Biodegradable polyphosphazenes are high-molecular-weight polymers with alternating nitrogen and phosphorus atoms in the backbone. This study is the first of its kind to systematically investigate the effect of side group structure on the compressive strength of novel biodegradable polyphosphazene based polymers as potential materials for tissue regeneration. The alanine polyphosphazene based polymers, poly(bis(ethyl alanato) phosphazene) (PNEA), poly((50% ethyl alanato) (50% methyl phenoxy) phosphazene) (PNEA(50)mPh(50)), poly((50% ethyl alanato) (50% phenyl phenoxy) phosphazene) (PNEA(50)PhPh(50)) were investigated to demonstrate their mechanical properties and osteocompatibility. Results of mechanical testing studies demonstrated that the nature and the ratio of the pendent groups attached to the polymer backbone play a significant role in determining the mechanical properties of the resulting polymer. The compressive strength of PNEA(50)PhPh(50) was significantly higher than poly(lactide-co-glycolide) (85:15 PLAGA) (p<0.05). Additional studies evaluated the cellular response and gene expression of primary rat osteoblast cells on PNEA, PNEA(50)mPh(50) and PNEA(50)PhPh(50) films as candidates for bone tissue engineering applications. Results of the in vitro osteocompatibility evaluation demonstrated that cells adhere, proliferate, and maintain their phenotype when seeded directly on the surface of PNEA, PNEA(50)mPh(50), and PNEA(50)PhPh(50). Moreover, cells on the surface of the polymers expressed type I collagen, alkaline phosphatase, osteocalcin, osteopontin, and bone sialoprotein, which are characteristic genes for osteoblast maturation, differentiation, and mineralization.

Development of biomaterial scaffold for nerve tissue engineering: Biomaterial mediated neural regeneration

Neural tissue repair and regeneration strategies have received a great deal of attention because it directly affects the quality of the patient's life. There are many scientific challenges to regenerate nerve while using conventional autologous nerve grafts and from the newly developed therapeutic strategies for the reconstruction of damaged nerves. Recent advancements in nerve regeneration have involved the application of tissue engineering principles and this has evolved a new perspective to neural therapy. The success of neural tissue engineering is mainly based on the regulation of cell behavior and tissue progression through the development of a synthetic scaffold that is analogous to the natural extracellular matrix and can support three-dimensional cell cultures. As the natural extracellular matrix provides an ideal environment for topographical, electrical and chemical cues to the adhesion and proliferation of neural cells, there exists a need to develop a synthetic scaffold that would be biocompatible, immunologically inert, conducting, biodegradable, and infection-resistant biomaterial to support neurite outgrowth. This review outlines the rationale for effective neural tissue engineering through the use of suitable biomaterials and scaffolding techniques for fabrication of a construct that would allow the neurons to adhere, proliferate and eventually form nerves.

Formation and properties of composites comprised of calcium-deficient hydroxyapatites and ethyl alanate polyphosphazenes

Composites comprised of calcium-deficient hydroxyapatite (HAp) and biodegradable polyphosphazenes were formed via cement-type reactions at physiologic temperature. The composite precursors were produced by blending particulate hydroxyapatite precursors with 10 wt% polymer using a solvent/non-solvent technique. HAp precursors having calcium-to-phosphate ratios of 1.5 (CDH) and 1.6 (CDS) were used. The polymeric constituents were poly[bis(ethyl alanato)phosphazene] (PNEA) and poly[(ethyl alanato)(1) (p-phenylphenoxy)(1) phosphazene] (PNEA(50)PhPh(50)). The effect of incorporating the phenyl phenoxy group was evaluated as a means of increasing the mechanical properties of the composites without retarding the rates of HAp formation. Reaction kinetics and mechanistic paths were characterized by pH determination, X-ray diffraction analyses, scanning electron microscopy, and infrared spectroscopy. The mechanical properties were analyzed by compression testing. These analyses indicated that the presence of the polymers slightly reduced the rate HAp formation. However, surface hydrolysis of polymer ester groups permitted the formation of calcium salt bridges that provide a mechanism for bonding with the HAp. The compressive strengths of the composites containing PNEA(50)PhPh(50) were superior to those containing PNEA, and were comparable to those of HAp produced in the absence of polymer. The current composites more closely match the structure of bone, and are thus strongly recommended to be used as bone cements where high loads are not expected.

Novel low temperature setting nanocrystalline calcium phosphate cements for bone repair: osteoblast cellular response and gene expression studies

Low temperature setting calcium phosphate cements (CPC) formed from reactive calcium phosphate precursors are receiving great attention in the fields of orthopaedics and tissue engineering. The purpose of this study was to evaluate the mechanical properties and osteocompatibility of a novel calcium deficient hydroxyapatite (CDSHA) with a Ca/P ratio of 1.6 developed in our laboratories and compare it to a previously developed calcium deficient hydroxyapatite (CDHA) with a Ca/P ratio of 1.5. The results demonstrated that the calcium-deficient hydroxyapatites (HA) formed from the CPCs were similar to biological HA at physiological temperature and the elastic moduli of CDHA and CDSHA were found to be 174.42 +/- 20.41 MPa (p < 0.05) and 115.86 +/- 24.8 MPa (p < 0.05), respectively. The surface morphologies of the two calcium deficient HA's formed were identical with a micro/nano porous structure as evidenced from SEM. The cellular proliferation on CDHA, and CDSHA, was comparable to the control, tissue culture polystyrene (TCPS) (p < 0.05). Alkaline phosphatase activity was significantly elevated on CDHA and CDSHA matrices at early time points when compared with the control (TCPS) (p < 0.05). Osteoblast cells gene expression on CDHA, and CDSHA showed type I collagen, alkaline phosphatase, osteocalcin, and osteopontin activity at both 7 and 14 days of culture. Thus, novel calcium-deficient HAs, CDHA, and CDSHA formed at low temperature are promising candidates for orthopaedic applications based on their ability to promote osteoblast cell adhesion and gene expression in vitro.

In vivo biodegradability and biocompatibility evaluation of novel alanine ester based polyphosphazenes in a rat model

Amino acid ester substituted polyphosphazenes are attractive candidates for various biomedical applications because of their biocompatibility, controllable hydrolytic degradation rates, and nontoxic degradation products. In this study, the biocompatibility of three L-alanine ethyl ester functionalized polyphosphazenes was evaluated in a subcutaneous rat model. The polymers used in the study were poly[bis(ethylalanato)phosphazene] (PNEA), poly[(50% ethylalanato) (50% methylphenoxy) phosphazene] (PNEA(50)mPh(50)), and poly[(50% ethylalanato)(50% phenyl phenoxy) phosphazene] (PNEA(50)PhPh(50)). Polymer disks of diameter 7.5 mm were prepared by a solvent evaporation technique and were implanted subcutaneously in rats. After 2, 4, and 12 weeks, the polymer along with the surrounding tissues were excised, prepared, and viewed by light microscopy to evaluate the tissue responses of the implanted polymers. The tissue responses were classified as minimal, mild, or moderate, based on a biocompatibility scheme developed in our laboratory. Minimal inflammation was characterized by the presence of few neutrophils, erythrocytes, and lymphocytes; mild response was characterized by the predominant presence of macrophages, fibroblasts, or giant cells; and moderate inflammation was characterized by the abundance of macrophages, giant cells, and by the presence of tissue exudates. The in vivo degradation profiles of the polymers at various time points were evaluated by gel permeation chromatography (GPC). PNEA and PNEA(50)mPh(50) matrices elicited varying levels of tissue responses during the 12-week implantation period. At 2 weeks both polymers evoked a moderate response, and by 12 weeks the response was found to be mild. However, PNEA(50)PhPh(50) elicited a mild response at the end of 2 weeks and demonstrated a further decreased inflammatory response after 12 weeks. The in vivo degradation of the polymers was followed by determining the molecular weights of the explanted polymer disks. PNEA and PNEA(50)mPh(50) disks showed significant decrease in molecular weight after 2 weeks of implantation. The molecular weights of PNEA and PNEA(50)mPh(50) residues could not be determined by GPC after 12 weeks of implantation because of almost complete degradation. On the other hand the in vivo degradation of PNEA(50)PhPh(50) was found to be slow, with a 63% loss in molecular weight in 12 weeks. Furthermore, this polymer maintained its shape and structure during the entire study. Thus, these polymers demonstrated excellent tissue compatibility and in vivo biodegradability and can be potential candidates for various biomedical applications.

A preliminary report on a novel electrospray technique for nanoparticle based biomedical implants coating: Precision electrospraying

The compatibility and biological efficacy of biomedical implants can be enhanced by coating their surface with appropriate agents. For predictable functioning of implants in situ, it is often desirable to obtain an extremely uniform coating thickness without effects on component dimensions or functions. Conventional coating techniques require rigorous processing conditions and often have limited adhesion and composition properties. In the present study, the authors report a novel precision electrospraying technique that allows both degradable and nondegradable coatings to be placed. Thin metallic slabs, springs, and biodegradable sintered microsphere scaffolds were coated with poly(lactide-co-glycolide) (PLAGA) using this technique. The effects of process parameters such as coating material concentration and applied voltage were studied using PLAGA and poly(ethylene glycol) coatings. Morphologies of coated surfaces were qualitatively characterized by scanning electron microscopy. Qualitative observations suggested that the coatings were composed of particles of various size/shape and agglomerates with different porous architectures. PLAGA coatings of uniform thickness were observed on all surfaces. Spherical nanoparticle poly(ethylene glycol) coatings (462-930 nm) were observed at all concentrations studied. This study found that the precision electrospraying technique is elegant, rapid, and reproducible with precise control over coating thickness (mum to mm) and is a useful alternative method for surface modification of biomedical implants.

Mantoux and contact positivity in tuberculosis

OBJECTIVE

To study the role of Mantoux and contact history in various forms of Childhood tuberculosis.

METHODS

605 children registered with TB clinic of Institute of Child Health and Hospital for Children, Chennai over a 5 year period from January 2000 to October 2005 with various forms of tuberculosis were recruited in the study. Clinical examination findings, basic investigations, chest skiagrams, computerized tomography (CT) wherever warranted, sputum or gastric aspirates for AFB smear, histopathology wherever possible were analyzed.

RESULTS

The study showed that Mantoux positivity in various forms of tuberculosis studied is 34.7%. The positivity of Mantoux was highest in lymph node tuberculosis (53%) and the lowest with CNS tuberculosis (21.2%). Among the other forms, Mantoux positivity was 36.4% in TB abdomen, 44.4% in Skeletal TB, 30.3% in pulmonary tuberculosis. The contact positivity was 30.4% in the sample studied.

CONCLUSION

The study also reflects that the extra pulmonary forms of tuberculosis seems to be more common in the pediatric population which constituted 79.8% of the cases included in the study.