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Low strength and rapid biodegradability of Acellular Dermal Matrix (ADM) restrict wider clinical application as rapid cell delivery platform in situ, for management of burn wounds. Herein, extracted ADM was modified by dual cross-linking approach with ionic crosslinking using chitosan (CTS) and covalent cross-linking using an iodine modified 2, 5-dihydro-2,5-dimethoxy-furan (DHF-I) cross-linker; termed as CsADM-Cl. In addition, inherent growth factors and cytokines were found to be preserved in the CsADM-Cl, irrespective of ionic/covalent crosslinking. CsADM-Cl demonstrated improvement in post crosslinking stiffness with decreased biodegradation rate. This hybrid crosslinked hydrogel supported adhesion, proliferation, and migration of human foreskin derived fibroblasts (HFCs) and keratinocytes (HKC). Also, the angiogenic potential of CsADM-Cl was manifested by chick chorioallantoic membrane (CAM) assay. CsADM-Cl showed excellent antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Moreover, CsADM-Cl treated full thickness (FT) burn wounds demonstrated rapid healing marked with superior angiogenesis, well-defined dermal-epidermal junctions (DEJ), mature basket weave collagen deposition, and development of more pronounced secondary appendages. Altogether, the bioactive CsADM-Cl hydrogel established significant clinical potential to support wound healing as an apt injectable antibacterial matrix to encounter unmet challenges concerning critical burn wounds.

Biomimetic delivery of osteoinductive growth factors via an osteoconductive matrix is an interesting approach for stimulating bone regeneration. In this context, the bone extracellular matrix (ECM) has been explored as an optimal delivery system, since it releases growth factors in a spatiotemporal manner from the matrix. However, a bone ECM hydrogel alone is weak, unstable, and prone to microbial contamination and also has been reported to have significantly reduced bone morphogenic protein-2 (BMP-2) post decellularization. In the present work, a microsphere embedded osteoinductive decellularized bone ECM/oleoyl chitosan based hydrogel construct (BOC) was developed as a matrix allowing dual delivery of an anti-resorptive drug (alendronate, ALN, via the microspheres) and BMP-2 (via the hydrogel) for a focal tibial defect in a rabbit model. The synthesized gelatin microspheres (GMs) were spherical in shape with diameter ∼32 μm as assessed by SEM analysis. The BOC construct showed sustained release of ALN and BMP-2 under the studied conditions. Interestingly, amniotic membrane-derived stem cells (HAMSCs) cultivated on the hydrogel construct demonstrated excellent biocompatibility, cell viability, and active proliferation potential. Additionally, cell differentiation on the constructs showed an elevated expression of osteogenic genes in an RT-PCR study along with enhanced mineralized matrix deposition as demonstrated by alkaline phosphatase (ALP) assay and alizarin red assay. The hydrogel construct was witnessed to have improved neo-vascularization potential in a chick chorioalantoic membrane (CAM) assay. Also, histological and computed tomographic findings evidenced enhanced bone regeneration in the group treated with the BOC/ALN/BMP hydrogel construct in a rabbit tibial defect model. To conclude, the developed multifunctional hydrogel construct acts as an osteoinductive and osteoconductive platform facilitating controlled delivery of ALN and BMP-2, essential for stimulating bone tissue regeneration.

Impaired skin regeneration in chronic wounds like in diabetes corresponds to high oxidative stress, poor angiogenesis and insufficient collagen hyperplasia. Therefore, a multifaceted strategy for treatment is required to address critical issues associated with chronic wound healing. Fascinating application of nanomaterials in chronic wounds is still limited; hence, in the present work bioactive solubilized decellularized dermal matrix (sADM) was employed to form a hydrogel with chitosan (CTS) at physiological pH/temperature and modified with reactive oxygen species (ROS) scavenging carbon nanodots (ND). A detailed in vitro investigation found that the ND modified bioactive hydrogel (CsADMND) is suitable for human amniotic membrane derived stem cell (hAMSC) delivery. Also, CsADMND was observed to possess a good ROS scavenging property, hemocompatibility and pro-angiogenic potential as demonstrated by 2,2-diphenyl-1-picrylhydrazyl (DPPH), haemolysis and chick chorioallantoic membrane (CAM) assay, respectively. The hybrid hydrogel promoted migration of cells in vitro in scratch assay owing to its antioxidant potential and the presence of bioactive moieties. Further, its efficacy in healing full thickness (FT) chronic wounds was evaluated in a streptozotocin (STZ) induced diabetic model. The CsADMND hydrogel after association with hAMSCs led to stimulation of early angiogenesis, superior collagen deposition, rapid wound closure, complete reepithelialisation, and formation of distinct organized dermal epidermal junctions (DEJ) post 21 days of healing. These results suggest that the hAMSC laden CsADMND hydrogel may serve as a promising therapeutic strategy for the management of chronic wounds.

Hydrogels derived from decellularized extracellular matrix (ECM) have been widely used as a bioactive matrix for facilitating functional bone tissue regeneration. However, its poor mechanical strength and fast degradation restricts the extensive use for clinical application. Herein, we present a crosslinked decellularized bone ECM (DBM) and fatty acid modified chitosan (oleoyl chitosan, OC) based biohybrid hydrogel (DBM/OC) for delivering human amnion-derived stem cells (HAMSCs) for bone regeneration. DBM/OC hydrogel were benchmarked against collagen-I/OC (Col-I/OC) based hydrogel in terms of their morphological characteristics, rheological analysis, and biological performances. DBM/OC hydrogel with its endogenous growth factors recapitulates the nanofibrillar 3D tissue microenvironment with improved mechanical strength and also exhibited antimicrobial potential along with superior proliferation/differentiation ability. HAMSCs encapsulation potential of DBM/OC hydrogel was established by well spread cytoskeleton morphology post 14 days of cultivation. Further, ex-vivo chick chorioallantoic membrane (CAM) assay revealed excellent neovascularization potential of DBM/OC hydrogel. Subcutaneously implanted DBM/OC hydrogel did not trigger any severe immune response or infection in the host after 21 days. Also, DBM/OC hydrogels and HAMSCs encapsulated DBM/OC hydrogels were implanted at the tibial defect in a rabbit model to assess the bone regeneration ability. Quantitative micro-CT and histomorphological analysis demonstrated that HAMSCs encapsulated DBM/OC hydrogel can support more mature mineralized bone formation at the defect area compared to DBM/OC hydrogel or SHAM. These findings manifested the efficacy of DBM/OC hydrogel as a functional cell-delivery vehicle and osteoinductive template to accelerate bone regeneration.

Nitrogen, sulfur, and phosphorous co-doped water-soluble carbon nanodots are synthesized from culinary waste onion peel powder (OPP) by a short microwave treatment. Onion Derived Carbon Nano Dots (OCND) that comprised hydrophilic group-decorated amorphous nano-dots exhibited bright, stable fluorescence at an excitation of 450 nm and emission wavelength at 520 nm along with a free radical scavenging property. The OCND exhibited excellent stability at different pH and UV exposure. Although extracted polyphenols degraded in the extract, interestingly it was shown to be cytocompatible and blood compatible as observed during cytotoxicity, fluorescence imaging of the cell and a hemolysis study. The present work not only focuses on the synthesis of OCND from the OPP extract but also provides an interesting fact that, even after the degradation of polyphenols in the extract, they are non-toxic to human cells (HFF & MG63) and RBCs. Moreover, OCND had no adverse effect on the migration rate of Human Foreskin-derived Fibroblasts (HFFs) as observed from a scratch assay. In addition to accelerating the migration rate of fibroblasts, the OCND altered intra- and extracellular reactive oxygen species (ROS) by enhancing the antioxidant mechanism of a fibroblast under oxidative stress. Further, OCND was observed to accelerate wound healing in a full thickness (FT) wound in a rat model for topical application, which can be attributed to its radical scavenging potential. In summary, this study leads to a new type of OCND synthesis route, which is inherently co-doped with phosphorous, sulfur and nitrogen and holds a great promise for a myriad of biological applications, including bio-imaging, free radical scavenging and wound healing.

Osteochondral injuries are challenging to repair due to their complex tissue anatomy and restricted self-repairing ability associated with a limited blood supply. Osteochondral tissue engineering is an important clinical aspect of the management and treatment of cartilage and underlying bone. In the present study, we fabricated human placenta-derived extracellular matrix sponges (PEMS) for repair of osteochondral tissue through a decellularization process. There were no significant cellular components present in the PEMS; hematoxylin & eosin/DAPI staining, DNA quantification and agarose gel electrophoresis were used to evaluate the extent of decellularization. Moreover, no significant alteration to the collagen and glycosaminoglycan (native extracellular matrix) content of the PEMS was observed. PEMS in vitro provided a non-cytotoxic environment rich in bioactive cues for human amniotic membrane-derived stem cells (HAMSCs) to proliferate in and differentiate into chondrogenic and osteogenic lineages under induction. Histological analysis at 28 days after the PEMS were subcutaneously implanted demonstrated no severe immune response in the host and supported the formation of blood vessels. To assess the osteochondral tissue repair ability of PEMS, cell-free PEMS (CFP) and cell-seeded PEMS (CSP) were implanted at osteochondral defect sites in a rabbit model. Histological scores indicated that osteochondral regeneration was more successful in the defects filled with CSP compared to those filled with CFP and empty defects (ED) after 60 days of implantation. In summary, a naturally derived biocompatible scaffold composed of extracellular matrix from human placenta has been successfully developed for osteochondral tissue engineering.

Impaired wound healing is primarily associated with inadequate angiogenesis, repressed cell migration, deficient synthesis of extracellular matrix (ECM) component/growth factors, and altered inflammatory responses in the wound bed environment. Herein, we report a simple process for the fabrication of PCL nanofiber mats embedded with placental-derived bioactive molecules (PCL–sPEM) rich in growth factors for full-thickness cutaneous wound healing. The physicochemical attributes and biological composition of PCL–sPEM nanofiber mats delivered a nontoxic environment in vitro and significantly promoted the adhesion, infiltration, and proliferation of human fibroblasts/keratinocytes. Conditioned media extracted from PCL–sPEM nanofiber mats enhanced the migration potential of the cells (fibroblasts/keratinocytes) involved in wound healing due to the release of growth factors embedded in it. Further, PCL–sPEM nanofiber mats attracted, stimulated and supported vascularization as determined by the Chick Chorioallantoic Membrane (CAM) assay. Interestingly, critical skin wounds of rats treated with PCL–sPEM nanofiber mats facilitated improved wound closure with well-organized dermis and epidermis, which could be ascribed to prominent vascularization, augmented migration of human foreskin fibroblasts (HFFs) & human epidermal keratinocytes (HEKs), increased collagen synthesis and early re-epithelialization. Collectively, our results suggest that PCL–sPEM nanofiber mats embedded with growth factors could be a suitable matrix for treating critical full-thickness wounds.

In the present work, a discrete dinuclear cadmium(II) complex Cd2(μ−H2L)(μ−OH)Cl2⋅H2O (1) and a dinuclear zinc(II) based 1D chain complex ({Zn2(L')(O2CCH3)}ClO4⋅3H2O)n (2) (where H3L = 2,6-bis{2-(2-hydroxyethylamino)ethylimino}methyl-4-methylphenol and H2L′ = bis-oxazoline (BOX) ligand), have been synthesized and characterized by single-crystal X-ray crystallography. The Cd2+ ions in the first case showed straight cut incorporation of metal ions within the ligand pockets. In case of zinc(II), the coordination induced oxazolidine ring formation resulted in macrocyclic ligand formation having two adjacent coordination pockets. In complex 2, the acetate ion acts as an O,O linker and joins the Zn2 nodes bound within the newly formed macrocyclic ligand bearing bis-oxazolidine rings to form 1D polymeric chain at the end. The H3L was next screened for its efficacy as selective fluorescence sensor for Mg2+ ions in aqueous MeOH medium. Steady state absorption and emission behaviour of H3L, 1 and 2 have been investigated. Time resolved fluorescence properties of H3L and the complexes 1 and 2 have been examined, and their lifetimes have been determined in 0.038–0.257 ns range. The cell viability in presence of H3L makes it a suitable candidate for application in live cell imaging studies.

Wound healing management is a major challenge for critical full-thickness skin wounds. Development of nanofibrous scaffolds with tunable wettability, degradation, and biocompatibility are highly desirable. Herein, we demonstrated synthesis of oleoyl chitosan (OC) by grafting monounsaturated fatty acid residue, C18 oleoyl chain, to the backbone of chitosan molecule and blending with gelatin to form the nanofiber mats. The physicochemical properties of the nanofiber mats revealed mechanical strength, moderate surface wettability, and suitable degradation rate. The nanofibrous mats showed excellent in vitro cytocompatibility with human amniotic membrane-derived stem cells (HAMSCs) in terms of enhanced adhesion and proliferation owing to biomimetic nanoarchitecture and chemical cues. Furthermore, the fabricated nanofiber was implanted with and without preseeded HAMSCs in the full-thickness wound to evaluate the skin wound healing efficacy in a rat model. Histological and immunohistochemical studies were condu...

Critical bone defects arising from traumatic injury and diseases are of major health concern since they are unable to heal spontaneously without clinical intervention. In this context, bone tissue engineering provides an attractive approach to treat bone defects by providing a bioactive template which has the potential to guide osseous tissue regeneration. In this study, porous hybrid placental extracellular matrix sponge (PIMS) was fabricated by a combinatorial method using silk fibroin (SF)/placental derived extracellular matrix and subsequently evaluated its efficacy towards bone tissue regeneration. The presence of intrinsic growth factors was evidenced by immunoblotting of the extracted proteins derived from the placental derived extracellular matrix. This growth factor rich PIMS lends a unique bioactive scaffolding to human amniotic mesenchymal stem cells (HAMSCs) which supported enhanced proliferation as well as superior osteogenic differentiation. Gene expression studies demonstrated significant up-regulation of osteogenic related genes in the PIMS group. PIMS when implanted in the chick chorioallantoic membrane, significantly attracted allantoic vessels revealing its potential to stimulate angiogenesis ex vivo. Furthermore, no severe immune response to the host was observed on subcutaneous implantation of PIMS in vivo. Instead, it supported the formation of blood vessels, revealing its outstanding biocompatibility. Additionally, critical tibial defects treated with PIMS demonstrated higher bone volume after six weeks when analyzed by micro-CT, which was accompanied by high mineral density. Histological and immunofluorescence studies validated the results and revealed enhanced osseous tissue regeneration after six weeks of surgery. All these findings recapitulated that the growth factors incorporated bioactive PIMS could perform as an appropriate matrix for osteogenic differentiation and efficient bone regeneration.

Regeneration of full-thickness wounds without scar formation is a multifaceted process, which depends on in situ dynamic interactions between the tissue-engineered skin substitutes and a newly formed reparative tissue. However, the majority of the tissue-engineered skin substitutes used so far in full-thickness wound healing cannot mimic the natural extracellular matrix (ECM) complexity and thus are incapable of providing a suitable niche for endogenous tissue repair. Herein, we demonstrated a simple approach to fabricate porous hybrid ECM sponges (HEMS) using a placental ECM and silk fibroin for full-thickness wound healing. HEMS with retained cytokines/growth factors provided a noncytotoxic environment in vitro for human foreskin fibroblasts (HFFs), human epidermal keratinocytes (HEKs), and human amniotic membrane-derived stem cells to adhere, infiltrate, and proliferate. Interestingly, HEMS-conditioned media accelerated the migration of HFFs and HEKs owing to the presence of cytokines/growth factors. Also, the ex vivo chick chorioallantoic membrane assay of HEMS demonstrated its excellent vascularization potential by inducing and supporting blood vessels. Additionally, HEMS when subcutaneously implanted demonstrated no severe immune response to the host. Furthermore, HEMS implanted in full-thickness wounds in a rat model showed augmented healing progression with well-organized epidermal-dermal junctions via pronounced angiogenesis, accelerated migration of HFFs/HEKs, enhanced granulation tissue formation, and early re-epithelialization. Taken together, these findings show that porous HEMS ornamented with cytokines/growth factors having superior physicomechanical properties may be an appropriate skin substitute for full-thickness cutaneous wounds.

Wound healing is a dynamic process wherein cells, and macromolecules work in consonance to facilitate tissue regeneration and restore tissue integrity. In the case of full-thickness (FT) wounds, healing requires additional support from native or synthetic matrices to aid tissue regeneration. In particular, a matrix with optimum hydrophilic-hydrophobic balance which will undergo adequate swelling as well as reduce bacterial adhesion has remained elusive. In the present study, polyurethane diol dispersion (PUD) and the anti-bacterial chitosan (Chn) were blended in different ratios which self-organized to form macroporous hydrogel scaffolds (MHS) at room temperature on drying. SEM and AFM micrographs revealed the macroporosity on top and fracture surfaces of the MHS. FTIR spectra revealed the intermolecular as well as intra-molecular hydrogen bonding interactions between the two polymers responsible for phase separation, which was also observed by micrographs of blend solutions during the drying process. The effect of phase separation on mechanical properties and in vitro degradation (hydrolytic, enzymatic and pH dependent) of MHS were studied and found to be suitable for wound healing. In vitro cytocompatibility was demonstrated by the proliferation of primary rat fibroblast cells on MHS. Selected MHS was subjected to in vivo FT wound healing study in Wistar rats and compared with an analogous polyurethane containing commercial dressing i.e. Tegaderm™. The MHS-treated wounds demonstrated accelerated healing with increased wound contraction, higher collagen synthesis, and vascularization in wound area compared to Tegaderm™. Thus, it is concluded that the developed MHS is a promising candidate for application as FT wound healing dressings.

The synthesis of two new lead(II) coordination polymers, [Pb 2 (mpic) 4 (H 2 O)]·0.5H 2 O ( 1 ) and [Pb 2 (phen) 2 (cit)(mes)]·2H 2 O ( 2 ) has been reported, where mpic=3-methyl picolinate, phen= o -phenanthroline, H 2 cit=citraconic acid, H 2 mes mesaconic acid. X-ray single crystal diffraction analyses showed that the complexes comprise topologically different 1D polymeric chains stabilized by weak interactions and both containing tetranuclear Pb 4 units connected by carboxylate groups. In compound 1 3-methylpicolinic acid is formed in situ from 3-methyl piconitrile, and mesaconate and citraconate anions were surprisingly formed from itaconic acid during the synthesis of 2. The photoluminescence and thermal properties of the complexes have been studied.

Reaction of salicylaldehyde thiosemicarbazone (H2L1), 2-hydroxyacetophenone thiosemicarbazone (H2L2) and 2-hydroxynaphthaldehyde thiosemicarbazone (H2L3) with Ni(ClO4)2·6H2O afforded dimeric complexes of type [{Ni(L)}2]. Reaction of these complexes with triphenylphosphine (PPh3), pyridine (py) and 4,4′-bipyridine (bpy) has yielded complexes of type [Ni(L)(PPh3)], [Ni(L)(py)] and [{Ni(L)}2(bpy)], respectively, which have also been obtained from reaction of the thiosemicarbazones with Ni(ClO4)2·6H2O and PPh3 or pyridine or 4,4′-bipyridine. Structures of the [{Ni(L)}2] complexes have been optimized by DFT calculations. Crystal structures of [Ni(L2)(PPh3)], [Ni(L2)(py)] and [{Ni(L1)}2(bpy)] have been determined. In all these complexes thiosemicarbazone is coordinated to nickel as ONS-donor. All these complexes show characteristic 1H NMR spectra and intense absorptions in the visible and ultraviolet region. Cyclic voltammetry on the complexes shows one irreversible oxidation on the positive side of SCE, and one irreversible reduction on the negative side. The mixed-ligand nickel complexes are found to be efficient catalysts for Heck type C–C coupling reactions. In vitro cytotoxicity screenings of the six mononuclear nickel complexes have been also carried out in a human tumor cell lines, viz. breast carcinoma cell line (MCF-7). [Ni(L3)(py)] shows the lowest LD50 value. An apoptosis study in MCF-7 with all the complexes confirms that at concentrations near LD50 they induce apoptosis.

Reaction of thiosemicarbazones of salicylaldehyde, 2-hydroxyacetophenone and 2-hydroxynaphthaldehyde with Ni(ClO4)2·6H2O, using 2,2′-bipyridine as coligand, afforded three dinuclear complexes (1a, 1b and 1c). Similar reactions using 2,2′:6′2″-terpyridine as coligand yielded three mononuclear complexes (2a, 2b and 2c). Crystal structures of 1b and 2a have been determined. In the dinuclear complexes, one nickel center is surrounded octahedrally by a dianionic O,N,S-donor thiosemicarbazone, a bipyridine and the bridging phenolate oxygen of the other thiosemicarbazone. The second nickel center adopts a square-planar geometry created by the second O,N,S-coordinated thiosemicarbazone and the bridging sulfur of the first thiosemicarbazone. In the mononuclear complexes nickel is complexed by a monoanionic O,N,S-coordinated thiosemicarbazone and a terpyridine, and the cationic species are isolated as perchlorate salts. All these six complexes are paramagnetic (μeff = 2.63–2.92 B.M.) and in dimethylsulfoxide solution they show intense absorptions in the visible and ultraviolet region, origin of which has been probed through DFT calculations. Cyclic voltammetry on the complexes shows one irreversible oxidation of coordinated thiosemicarbazone on the positive side of SCE, and one irreversible reduction of the coordinated polypyridine ligand on the negative side. These nickel complexes are found to be efficient catalysts for Suzuki cross-coupling reactions.

Excited state intramolecular proton transfer (ESIPT) of 2-hydroxy-1-naphthaldehyde semicarbazone (2HNS) has been studied in n-heptane and methanol solvents exploiting absorption, steady state and time-resolved fluorometric techniques. Experimental results reveal that although the intramolecular proton transfer (IPT) reaction does not take place in the ground state (S 0 ), the process is feasible in the lowest excited singlet state (S 1 ). Ab initio quantum chemical calculations have been carried out to judge the feasibility of the IPT process in the different electronic states. Density functional theory (DFT) has been used for the ground state calculations while those relevant to the lowest excited singlet state have been performed exploiting the time dependent density functional theory (TDDFT) using the B3LYP functional at 6-31G** level. The distances of the transferable hydrogen from the oxygen atom (wherefrom it is dislocated during the IPT reaction) as well as the nitrogen atom (to which it gets attached) have been taken as the independent reaction coordinates. The calculations reveal that either of these two parameters may be used to monitor the progress of the prototropic process since both lead to the same prototropic species passing through the same transition state. Simulation of the potential energy curves (PECs) and potential energy surfaces (PESs) leads to visualize the advancement of the reaction. Calculations imply that formation of the tautomer in the S 0 state leads to endothermicity, while the process is exothermic in the S 1 state. The calculated activation energy ( E act ) of the process also decreases in the excited state. Thus, although the reaction is not feasible in the ground state, both the thermodynamic (Δ H ) and the kinetic ( E act ) factors favor the prototropic process to occur in the S 1 state. This article reveals that any of the suitably and logically chosen structural parameters giving the same value of the reaction parameters and resulting in the same transition state may serve as the reaction co-ordinate.

Reaction of the 4-R-benzaldehyde thiosemicarbazones (denoted in general as L-R; R = OCH3, CH3, H, Cl and NO2) with trans-[Pd(PPh3)2Cl2] afforded a group of mixed-ligand complexes (denoted in general as 1-R) incorporating a N,S-coordinated thiosemicarbazone, a triphenylphosphine and a chloride. Similar reaction with Na2[PdCl4] afforded a family of bis-thiosemicarbazone complexes (denoted in general as 2-R), where each ligand is N,S-coordinated. Crystal structures of 1-CH3, 1-NO2, 2-OCH3, 2-NO2 and L-NO2 have been determined. In all the complexes the thiosemicarbazones are coordinated to the metal center, via dissociation of the acidic proton, as bidentate N,S-donors forming five-membered chelate rings. With reference to the structure of the uncoordinated thiosemicarbazone, this coordination mode is associated with a conformational change around the C N bond. All the 1-R and 2-R complexes display intense absorptions in the visible region. Catalytic activity of the 1-R and 2-R complexes towards some C–C coupling reactions (e.g. Suzuki, Heck and Sonogashira) has been examined and while both are found to be efficient catalysts, 1-R is much better catalyst than 2-R.

Radiopaque polymer derivatives were successfully prepared through surface diffusion mediated cross-linking of chitosan with iodinated 2,5-dimethoxy-2,5-dihydrofuran. The incorporation of iodine in 2,5-dimethoxy-2,5-dihydrofuran was validated by (1)H NMR and mass spectroscopy. The cross-linking of the glucosamine moieties of chitosan with the iodinated product was confirmed by (13)C NMR and energy-dispersive X-ray spectroscopy. Radiography analysis proved inherent opacity of the iodinated fibrous sheets and microspheres that were comparable to the X-ray visibility of aluminum hollow rings of equivalent thickness and commercially available radiopaque tape, respectively. Microscopic studies evidenced retention of the fiber/microsphere morphology after the iodination/cross-linking reactions. The effects of iodination/cross-linking on the mechanical and biodegradation properties of fibers were studied by nanoindentation and enzymatic assay, respectively. In vitro and in vivo studies established the nontoxic, biodegradable nature of radiopaque derivatives. Iodinated fiber mesh implanted in a rabbit model was significantly X-ray opaque compared to the uncross-linked fiber mesh and medical grade surgical swabs. Further, opacity of the iodinated mesh was evident even after 60 days, though the intensity was reduced, which indicates the biodegradable nature of the iodinated polymer. The opacity of the iodinated sutures was also established in the computed tomography images. Finally, the sufficient in vivo contrast property of the radiopaque microspheres in the gastrointestinal tract indicates its possible role in clinical diagnostics.

A variety of mononuclear palladium and heterobinuclear Pd—Ru N,N,O-pincer complexes is synthesized and studied in Suzuki, Heck and Sonogashira cross-coupling.

The reaction of a 1 : 1 mixture of 4-R-benzaldehyde thiosemicarbazone [denoted in general as HL–R; where H stands for the dissociable acidic proton and R (R = OCH3, CH3, H, Cl and NO2) for the substituent] and 1-nitroso-2-naphthol (abbreviated as Hnn), with an equivalent quantity of Na2[PdCl4] in ethanolic medium affords a group of mixed-ligand complexes of the type [Pd(L–R)(nn)]. A similar reaction of a mixture of HL–R and quinolin-8-ol (Hq) with Na2[PdCl4] affords another family of mixed-ligand complexes of the type [Pd(L–R)(q)]. Crystal structures of [Pd(L–Cl)(nn)], [Pd(L–CH3)(q)] and [Pd(L–Cl)(q)] have been determined. In all the complexes the thiosemicarbazones are coordinated to the metal center, via dissociation of the acidic proton, as monoanionic bidentate N,S-donors forming five-membered chelate rings. In the [Pd(L–R)(nn)] complexes, the 1-nitroso-2-naphtholate anion is coordinated as a N,O-donor forming a five-membered chelate ring. Similarly in the [Pd(L–R)(q)] complexes, the quinolin-8-olate anion is bound to the metal center in the N,O-mode forming a five-membered chelate ring. All the [Pd(L–R)(nn)] and [Pd(L–R)(q)] complexes show characteristic 1H NMR signals, and in dichloromethane solution they all display intense absorptions in the visible and ultraviolet regions. Catalytic activities of the [Pd(L–R)(nn)] and [Pd(L–R)(q)] complexes have been examined towards some C–C and C–N coupling reactions, where both were found to show notable catalytic efficiency.

Reaction of salicylaldehyde semicarbazone (L1), 2-hydroxyacetophenone semicarbazone (L2), and 2-hydroxynaphthaldehyde semicarbazone (L3) with [Pd(PPh3)2Cl2] in ethanol in the presence of a base (NEt3) affords a family of yellow complexes (1a, 1b and 1c, respectively). In these complexes the semicarbazone ligands are coordinated to palladium in a rather unusual tridentate ONN-mode, and a PPh3 also remains coordinated to the metal center. Crystal structures of the 1b and 1c complexes have been determined, and structure of 1a has been optimized by a DFT method. In these complexes two potential donor sites of the coordinated semicarbazone, viz. the hydrazinic nitrogen and carbonylic oxygen, remain unutilized. Further reaction of these palladium complexes (1a, 1b and 1c) with [Ru(PPh3)2(CO)2Cl2] yields a family of orange complexes (2a, 2b and 2c, respectively). In these heterodinuclear (Pd–Ru) complexes, the hydrazinic nitrogen (via dissociation of the N–H proton) and the carbonylic oxygen from the palladium-containing fragment bind to the ruthenium center by displacing a chloride and a carbonyl. Crystal structures of 2a and 2c have been determined, and the structure of 2b has been optimized by a DFT method. All the complexes show characteristic 1H NMR spectra and, intense absorptions in the visible and ultraviolet region. Cyclic voltammetry on all the complexes shows an irreversible oxidation of the coordinated semicarbazone within 0.86–0.93 V vs. SCE, and an irreversible reduction of the same ligand within −0.96 to −1.14 V vs. SCE. Both the mononuclear (1a, 1b and 1c) and heterodinuclear (2a, 2b and 2c) complexes are found to efficiently catalyze Suzuki, Heck and Sonogashira type C–C coupling reactions utilizing a variety of aryl bromides and aryl chlorides. The Pd–Ru complexes (2a, 2b and 2c) are found to be better catalysts than the Pd complexes (1a, 1b and 1c) for Suzuki and Heck coupling reactions.

Reaction of salicylaldehyde thiosemicarbazone (L-1), 2-hydroxyacetophenone thiosemicarbazone (L-2) and 2-hydroxynapthaldehyde thiosemicarbazone (L-3) with [Ru(dmso)(4)Cl-2] affords a family of three dimeric complexes (1), (2) and (3) respectively. Crystal structure of the complex (3) has been determined. In these complexes, each monomeric unit consists of one ruthenium center and two thiosemicarbazone ligands, one of which is coordinated to ruthenium as O,N,S-donor and the other as N,S-donor forming a five-membered chelate ring. Two such monomeric units remain bridged by the sulfur atoms of the O,N,S-coordinated thiosemicarbazones. Due to this sulfur bridging, the two ruthenium centers become so close to each other, that a ruthenium-ruthenium single bond is also formed. All the complexes are diamagnetic in the solid state and in dimethylsulfoxide solution show intense absorptions in the visible and ultraviolet region. Origin of these spectral transitions has been established from DFT calculations. Cyclic voltammetry on the complexes shows two irreversible ligand oxidations on the positive side of SCE and two irreversible ligand reductions on the negative side.