Development of a new flexor tendon repair technique performed with bioabsorbable poly-L/D-lactide (PLDLA) suture

Sormen koukistajajännevamman korjauksen jälkeisen aktiivisen mobilisaation on todettu johtavan parempaan toiminnalliseen lopputulokseen kuin nykyisin yleisesti käytetyn dynaamisen mobilisaation. Aktiivisen mobilisaation ongelma on jännekorjauksen pettämisriskin lisääntyminen nykyisten ommeltekniikoiden riittämättömän vahvuuden vuoksi. Jännekorjauksen lujuutta on parannettu kehittämällä monisäieommeltekniikoita, joissa jänteeseen tehdään useita rinnakkaisia ydinompeleita. Niiden kliinistä käyttöä rajoittaa kuitenkin monimutkainen ja aikaa vievä tekninen suoritus. Käden koukistajajännekorjauksessa käytetään yleisesti sulamattomia ommelmateriaaleja. Nykyiset käytössä olevat biohajoavat langat heikkenevät liian nopeasti jänteen paranemiseen nähden. Biohajoavan laktidistereokopolymeeri (PLDLA) 96/4 – langan vetolujuuden puoliintumisajan sekä kudosominaisuuksien on aiemmin todettu soveltuvan koukistajajännekorjaukseen. Tutkimuksen tavoitteena oli kehittää välittömän aktiivisen mobilisaation kestävä ja toteutukseltaan yksinkertainen käden koukistajajännekorjausmenetelmä biohajoavaa PLDLA 96/4 –materiaalia käyttäen. Tutkimuksessa analysoitiin viiden eri yleisesti käytetyn koukistajajänneompeleen biomekaanisia ominaisuuksia staattisessa vetolujuustestauksessa ydinompeleen rakenteellisten ominaisuuksien – 1) säikeiden (lankojen) lukumäärän, 2) langan paksuuden ja 3) ompeleen konfiguraation – vaikutuksen selvittämiseksi jännekorjauksen pettämiseen ja vahvuuteen. Jännekorjausten näkyvän avautumisen todettiin alkavan perifeerisen ompeleen pettäessä voima-venymäkäyrän myötöpisteessä. Ydinompeleen lankojen lukumäärän lisääminen paransi ompeleen pitokykyä jänteessä ja suurensi korjauksen myötövoimaa. Sen sijaan paksumman (vahvemman) langan käyttäminen tai ompeleen konfiguraatio eivät vaikuttaneet myötövoimaan. Tulosten perusteella tutkittiin mahdollisuuksia lisätä ompeleen pitokykyä jänteestä yksinkertaisella monisäieompeleella, jossa ydinommel tehtiin kolmen säikeen polyesterilangalla tai nauhamaisen rakenteen omaavalla kolmen säikeen polyesterilangalla. Nauhamainen rakenne lisäsi merkitsevästi ompeleen pitokykyä jänteessä parantaen myötövoimaa sekä maksimivoimaa. Korjauksen vahvuus ylitti aktiivisen mobilisaation jännekorjaukseen kohdistaman kuormitustason. PLDLA 96/4 –langan soveltuvuutta koukistajajännekorjaukseen selvitettiin tutkimalla langan biomekaanisia ominaisuuksia ja solmujen pito-ominaisuuksia staattisessa vetolujuustestauksessa verrattuna yleisimmin jännekorjauksessa käytettävään punottuun polyesterilankaan (Ticron®). PLDLA –langan todettiin soveltuvan hyvin koukistajajännekorjaukseen, sillä se on polyesterilankaa venymättömämpi ja solmujen pitävyys on parempi. Viimeisessä vaiheessa tutkittiin PLDLA 96/4 –langasta valmistetulla kolmisäikeisellä, nauhamaisella jännekorjausvälineellä tehdyn jännekorjauksen kestävyyttä staattisessa vetolujuustestauksessa sekä syklisessä kuormituksessa, joka simuloi staattista testausta paremmin mobilisaation toistuvaa kuormitusta. PLDLA-korjauksen vahvuus ylitti sekä staattisessa että syklisessä kuormituksessa aktiivisen mobilisaation edellyttämän vahvuuden. Nauhamaista litteää ommelmateriaalia ei aiemmin ole tutkittu tai käytetty käden koukistajajännekorjauksessa. Tässä tutkimuksessa ommelmateriaalin nauhamainen rakenne paransi merkitsevästi jännekorjauksen vahvuutta, minkä arvioidaan johtuvan lisääntyneestä kontaktipinnasta jänteen ja ommelmateriaalin välillä estäen ompeleen läpileikkautumista jänteessä. Tutkimuksessa biohajoavasta PLDLA –materiaalista valmistetulla rakenteeltaan nauhamaisella kolmisäikeisellä langalla tehdyn jännekorjauksen vahvuus saavutti aktiivisen mobilisaation edellyttämän tason. Lisäksi uusi menetelmä on helppokäyttöinen ja sillä vältetään perinteisten monisäieompeleiden tekniseen suoritukseen liittyvät ongelmat.

Bioabsorbable materials for osteosynthesis and small joint arthroplasty in the hand

Fractures and arthritic joint destruction are common in the hand. A reliable and stable fracture fixation can be achieved by metal implants, which however, become unnecessary or even harmful after consolidation. The silicone implant arthroplasty is the current method of choice for reconstruction of metacarpophalangeal joints in rheumatoid patients. However, the outcome tends to worsen with long-term follow-up and implant-related complications become frequent. To address these problems, bioabsorbable implants were designed for the hand area. Aims of the studies were: 1) to evaluate the biomechanical stabilities provided by self- reinforced (SR) bioabsorbable implants in a transverse and an oblique osteotomy of small tubular bones and to compare them with those provided by metal implants; 2) to evaluate the SR poly-L/DL-lactide 70/30 plate for osteosynthesis in a proof-of-principle type of experiment in three cases of hand injuries; and 3) to evaluate the poly-L/D-lactide (PLA) 96/4 joint scaffold, a composite joint implant with a supplementary intramedullary Polyactive® stem and Swanson silicone implant in an experimental small joint arthroplasty model. Methods used were: 1) 112 fresh frozen human cadaver and 160 pig metacarpal bones osteotomised transversally or obliquely, respectively, and tested ex vivo in three point bending and in torsion; 2) three patient cases of complex hand injuries; and 3) the fifth metacarpophalangeal joints reconstructed in 18 skeletally-mature minipigs and studied radiologically and histologically. The initial fixation stabilities provided by bioabsorbable implants in the tubular bones of the hand were comparable with currently-employed metal fixation techniques, and were sufficient for fracture stabilisation in three preliminary cases in the hand. However, in torsion the stabilities provided by bioabsorbable implants were lower than that provided by metal counterparts. The bioabsorbable plate enhanced the bending stability for the bioabsorbable fixation construct. PLA 96/4 joint scaffolds demonstrated good biocompatibility and enabled fibrous tissue in-growth in situ. After scaffold degradation, a functional, stable pseudarthrosis with dense fibrous connective tissue was formed. However, the supplementary Polyactive® stem caused a deleterious tissue reaction and therefore the stem can not be applied to the composite joint implant. The bioabsorbable implants have potential for use in clinical hand surgery, but have to await validation in clinical patient series and controlled trials.

One-dimensional zig-zag type coordination polymers of Ni(II) and Cu(II) containing 1,3-benzenedicarboxylate and 1,3-diaminopropane: Structural, spectral and thermal studies

Two coordination polymers [Ni(ipt)(dap)(2)](n) (1) and [Cu(ipt)(dap)H2O](n) center dot nH(2)O (2) with an overall one-dimensional arrangement and having isophthalate (ipt) as bridging moieties and chelating 1,3-diaminopropane (dap) as structure modulating units have been prepared and characterized by crystallographic, spectroscopic and thermo-analytical studies. Both have an overall one-dimensional zig-zag nature but with a distorted octahedral NiN4O2 chromophore for 1 and a distorted square pyramidal CuN2O3 chromophore for 2. Even though the ipt units are acting as bridging units through mono-dentatively coordinating carboxylate functions in both polymers, compound 1 has the carboxylate oxygen linkages at the trans positions, while in 2 the oxygen linkages occur at the cis positions leading to a different type of zig-zag arrangement. Relevant spectral and bonding parameters also could be evaluated for the compounds using UV-Vis and EPR spectra. Thermal stability and possible structural modifications on thermal treatment of the compounds were also investigated and the relevant thermodynamic and kinetic parameters evaluated from the thermal data. (C) 2007 Elsevier B.V. All rights reserved.

Understanding the folding process of synthetic polymers by small-molecule folding agents

Two acceptor containing polyimides PDI and NDI carrying pyromellitic diimide units and 1,4,5,8-naphthalene tetracarboxy diimide units, respectively, along with hexa(oxyethylene) (EO6) segments as linkers, were prepared from the corresponding dianhydrides and diamines. These polyimides were made to fold by interaction with specifically designed folding agents containing a dialkoxynaphtha-lene (DAN) donor linked to a carboxylic acid group. The alkali-metal counter-ion of the donor carboxylic acid upon complexation with the EO6 segment brings the DAN unit in the right location to induce a charge-transfer complex formation with acceptor units in the polymer backbone. This two-point interaction between the folding agent and the polymer backbone leads to a folding of the polymer chain, which was readily monitored by NMR titrations. The effect of various parameters, such as structures of the folding agent and polymer, and the solvent composition, on the folding propensities of the polymer was studied.

Photophysics of conjugated polymers: interplay between Forster energy migration and defect concentration in shaping a photochemical funnel in PPV

Recent single molecule experiments have suggested the existence of a photochemical funnel in the photophysics of conjugated polymers, like poly[2-methoxy-5-(2'-ethylhexyl)oxy-1,4-phenylenevinylene] (MEH-PPV). The funnel is believed to be a consequence of the presence of conformational or chemical defects along the polymer chain and efficient non-radiative energy transfer among different chromophore segments. Here we address the effect of the excitation energy dynamics on the photophysics of PPV. The PPV chain is modeled as a polymer with the length distribution of chromophores given either by a Gaussian or by a Poisson distribution. We observe that the Poisson distribution of the segment lengths explains the photophysics of PPV better than the Gaussian distribution. A recently proposed version of an extended particle-in-a-box' model is used to calculate the exciton energies and the transition dipole moments of the chromophores, and a master equation to describe the excitation energy transfer among different chromophores. The rate of energy transfer is assumed to be given here, as a first approximation, by the well-known Forster expression. The observed excitation population dynamics confirms the photochemical funneling of excitation energy from shorter to longer chromophores of the polymer chain. The time scale of spectral shift and energy transfer for our model polymer, with realistic values of optical parameters, is in the range of 200-300 ps. We find that the excitation energy may not always migrate towards the longest chromophore segments in the polymer chain as the efficiency of energy transfer between chromophores depends on the separation distance between the two and their relative orientation.

Flame retardant polyphosphate esters: 1. Condensation polymers of bisphenols with aryl phosphorodichloridates: synthesis, characterization and thermal studies

Polyphosphate esters were synthesized by the solution polycondensation of bisphenols with aryl phosphorodichloridates. The polymers were characterized by i.r. and 1H, 13C and 31P n.m.r. spectroscopy. The molecular weights were determined by end group analysis using 1H and 31P n.m.r. spectral data. The thermal stability of the polymers was analysed by thermogravimetry.

Flame retardant polyphosphate esters: 2. Condensation polymers of bisphenol A with alkyl phosphorodichloridates: synthesis, characterization and thermal studies

Polyphosphate esters based on bisphenol A and alkyl phosphorodichloridates have been synthesized and characterized by i.r. and n.m.r. spectroscopy. The molecular weights were calculated from 31P n.m.r. The thermal stability of the polymers were analysed by thermogravimetry.

A dragonfly inspired flapping wing actuated by electro active polymers

An energy-based variational approach is used for structural dynamic modeling of the IPMC (Ionic Polymer Metal Composites) flapping wing. Dynamic characteristics of the wing are analyzed using numerical simulations. Starting with the initial design, critical parameters which have influence on the performance of the wing are identified through parametric studies. An optimization study is performed to obtain improved flapping actuation of the IPMC wing. It is shown that the optimization algorithm leads to a flapping wing with dimensions similar to the dragonfly Aeshna Multicolor wing. An unsteady aerodynamic model based on modified strip theory is used to obtain the aerodynamic forces. It is found that the IPMC wing generates sufficient lift to support its own weight and carry a small payload. It is therefore a potential candidate for flapping wing of micro air vehicles.

Mixed Azide and 5-(Pyrimidyl)tetrazole Bridged Co(II)/Mn(II) Polymers: Synthesis, Crystal Structures, Ferroelectric and Magnetic Behavior

The reaction of pyrimidine-2-carbonitrile, NaN3 in the presence of Co(NO3)(2)center dot 6H(2)O or MnCl2 center dot 4H(2)O leads to the formation of complexes Co(pmtz)(mu(1,3)-N-3)(H2O)](n) (1) and Mn(pmtz)(mu(1,3)-N-3)(H2O)](n) (2) respectively, under hydrothermal condition pmtz =5-(pyrimidyl)tetrazolate]. These two complexes have been fully characterized by single crystal X-ray diffraction. Complex 1 crystallizes in a non-centrosymmetric space group Aba2 in the orthorhombic system and is found to exhibit ferroelectric behavior, whereas complex 2 crystallizes in the P2(1)/c space group in the monoclinic system. Variable temperature magnetic characterizations in the temperature range of 2-300 K indicate that complex 1 is a canted antiferromagnet (weak ferromagnet) with T-c = 15.9 K. Complex 1 represents a unique example of a multiferroic coordination polymer containing tetrazole as a co-ligand. Complex 2 is a one-dimensional chain of Mn(II) bridged by a well-known antiferromagnetic coupler end-to-end azido ligand. In contrast to the role played by the end-to-end azido pathway in most of the transition metal complexes, complex 2 showed unusual ferromagnetic behavior below 40 K because of spin canting.

Synthesis, crystal structures and magnetic behavior of two 3D coordination polymers using N-(4/3-arboxyphenyl)iminodiacetic acids as bridging ligands

Research on structure and magnetic properties of polynuclear metal complexes to understand the structural and chemical factors governing the electronic exchange coupling mediated by multi-atom bridging ligands is of growing interest. Hydrothermal treatment of Ni(NO3)(2)center dot 6H(2)O with N-(4-carboxyphenyl)iminodiacetic acid N-4(H(3)CPIDA)] at 150 degrees C yielded a 3D coordination polymer of general formula Ni-3{N-4( CPIDA)}(2)(H2O)(3)]center dot 6H(2)O (1). An analogous network of general formula Co-3{N-3(CPIDA)}(2)(H2O)(3)]center dot 3H(2)O (2) was synthesized using N-(3-carboxyphenyl) iminodiacetic acid N-3(H(3)CPIDA)] in combination with Co(NO3)(2)center dot 6H(2)O under identical reaction condition. Both the complexes contain trinuclear secondary building unit, and crystallized in monoclinic system with space groups C2/c (1) and P2(1)/c (2), respectively. Variable temperature magnetic characterization of these complexes in the temperature range of 2-300 K indicated the presence of overall ferromagnetic and antiferromagnetic behavior for 1 and 2, respectively. Density functional theory calculations (B3LYP functional) were performed for further insight on the trinuclear units to provide a qualitative theoretical interpretation on the overall magnetic behavior of the complexes 1 and 2. (C) 2010 Elsevier B.V. All rights reserved.

A Series of Cu-II-Azide Polymers of Cu-6 Building Units and the Role of Chelating Diamine in Controlling their Dimensionality: Synthesis, Structures, and Magnetic Behavior

Four new neutral copper-azido polymers Cu-6(N-3)(12)(aem)(2)](n)(1), Cu-6(N-3)(12)(dmeen)(2)(H2O)(2)](n) (2), Cu-6(N-3)(12)(N,N'-dmen)(2)](n) (3), and Cu-6(N-3)(12)(hmpz)(2)](n) (4) aem = 4-(2-aminoethyl)morpholine; dmeen = N,N-dimethyl-N'-ethylethylenediamine; N,N'-dmen = N,N'-dimethylethylenediamine and hmpz = homopiperazine] have been synthesized by using 0.33 mol equiv of the chelating diamine ligands with Cu(NO3)(2)center dot 3H(2)O/CuCl2 center dot 2H(2)O and an excess of NaN3. Single crystal X-ray structures show that the basic unit of these complexes, especially 1-3, contains very similar Cu-6(II) building blocks. But the overall structures of these complexes vary widely in dimensionality. While 1 is three-dimensional (3D) in nature, 2 and 3 have a two-dimensional (2D) arrangement (with different connectivity) and 4 has a one-dimensional (1D) structure. Cryomagnetic susceptibility measurements over a wide range of temperature exhibit dominant ferromagnetic behavior in all the four complexes. The experimental susceptibility data have been analyzed by some theoretical model equations.

Band to correlated crossover in alternating Hubbard and Pariser-Parr-Pople chains: Nature of the lowest singlet excitation of conjugated polymers

The evolution with increasing Coulomb correlations of a semiconductor to a magnetic insulator is related to an excited-state crossover in pi-electron models for conjugated polymers. We associate strong fluorescence with a lowest singlet excitation S1 that is dipole allowed, on the band side, while S1 becomes two-photon allowed on the correlated side. S1/S2 crossovers in Hubbard, Pariser-Parr-Pople, or other chains with electron-hole symmetry and alternating transfer integral t(1 +/- delta) are based on exact results at delta=0 and 1, on molecular exciton theory at large delta, and on oligomer calculations up to twelve sites.