Izrada i karakterizacija IPN alginatnih i želatinskih mikrogelova s tramadolom: Optimiranje pomoću metode odzivnih površina

Tramadol-loaded interpenetrating polymer network (IPN) alginate-gelatin (AG) microgels (MG) were prepared by the chemical cross-linking technique with glutaraldehyde as cross-linking agent and were optimized using response surfaces. A central composite design for 2 factors, at 3 levels each, was employed to evaluate the effect of critical formulation variables, namely the amount of gelatin (X1) and glutaraldehyde (X2) on geometric mean diameter, encapsulation efficiency, diffusion coefficient (D), amount of mucin adsorbed per unit mass (Qe) and 50 % drug release time (t50). Microgels with average particle size in the range of 44.31102.41 m were obtained. Drug encapsulation up to 86.5 % was achieved. MGs were characterized by FT-IR spectroscopy to assess formation of the IPN structure and differential scanning calorimetry (DSC) was performed to understand the nature of drug dispersion after encapsulation into IPN microgels. Both equilibrium and dynamic swelling studies were performed in pH 7.4 phosphate buffer. Diffusion coefficients and exponents for water transport were determined using an empirical equation. The mucoadhesive properties of MGs were evaluated in aqueous solution by measuring the mucin adsorbed on MGs. Adsorption isotherms were constructed and fitted with Freundlich and Langmuir equations. In vitro release studies indicated the dependence of drug release on the extent of crosslinking and amount of gelatin used in preparing IPNs. The release rates were fitted to power law equation and Higuchi’s model to compute the various drug transport parameters, n value ranged from 0.4055 to 0.5754, suggesting that release may vary from Fickian to quasi-Fickian depending upon variation in the formulation composition.Interpenetrirajući umreženi polimerni (IPN) alginatno-želatinski (AG) mikrogelovi (MG) tramadola pripravljeni su metodom umrežavanja koristeći glutaraldehid kao sredstvo za umrežavanje. Pripravci su optimirani pomoću odzivnih površina. Kompozitini dizajn s dva faktora na tri nivoa upotrijebljen je za procjenu kritičnih formulacijskih varijabli: praćen je utjecaj količine želatine (X1) i glutaraldehida (X2) na prosječnu veličinu čestica, sposobnost kapsuliranja, koeficijent difuzije (D), količinu adsorbiranog mucina po jedinici mase (Qe) i vrijeme potrebno za oslobađanje 50 % lijeka (t50). Dobiveni su mikrogelovi prosječne veličine čestica od 44,31 do 102,41 m, a maksimalno postignuto vezanje lijeka bilo je 86,5 %. Mikrogelovi su karakterizirani FT-IR spektroskopijom i diferencijalnom pretražnom kalorimetrijom (DSC). Ravnotežne i dinamičke studije bubrenja provedene su u fosfatnom puferu pH 7,4. Koeficijenti difuzije i eksponenti za transport vode određeni su pomoću empirijske jednadžbe. Mukoadhezivna svojstva MGs evaluirana su u vodenoj otopini mjerenjem adsorpcije mucina na mikrogelove. Konstruirane su adsorpcijske izoterme i uspoređene s Freudlichovim i Langmuirovim jednadžbama. Pokusi in vitro pokazuju da oslobađanje ljekovite tvari ovisi o stupnju umreženja i količini želatine upotrijebljene u pripravi IPN. Vrijednosti oslobađanja uvrštene su u jednadžbu zakona potencije i u Higuchijev model kako bi se izračunali razni parametri prijenosa lijeka; n vrijednosti bile su između 0,4055 i 0,5754, što ukazuje na to da oslobađanje varira od Fickovog do kvazi-Fickovog, ovisno o sastavu pripravka

Polarographic determination of Pb(II) and Cd(II) with selective removal of Se(IV) using ionic poly(N,N-dimethylacrylamide-co-allylthiourea)

Hydrogels based on N,N-dimethylacrylamide (DMAAm), allylthiourea (ATU), and maleic acid (MA) were synthesized by free-radical cross-linking copolymerization in water with N,N-methylene-bis(acrylamide) (BAAm) as the cross-linker, ammonium persulfate (APS) as the initiator, and N,N,N',N'-tetramethyl-enediamine (TEMED) as the activator. Since Se(IV) is the most serious interfering element in the electroanalytical (polarographic or voltammetric) determination of lead and cadmium, a new method for their correct determination after selective separation of the interfering ion (selenite) was developed by using poly(N,N-dimethylacrylamide-co-allylthiourea) [P(DMAAm-co-ATU)] hydrogels containing reducing pedant groups like allylthiourea. The proposed method showed good reproducibility and accuracy with relative standard deviations of 8.5 and 3.4% and relative errors of -6.0 and -5.4% for the determination of 5.0 x 10(-5) M Pb(II) and Cd(II), respectively, next to 3.0 x 10(-5) M Se(IV)

Chemisorption of 3-aminopropyltrimethoxysilane on Si(001)-(2 x 2)

The results of an ab initio calculation, based on pseudopotentials and the density functional theory, for the atomic and electronic structures of the chemisorption of 3-aminopropyltrimethoxysilane (APTS) on the Si(001)-(2 x 2) surface are presented. Two possible models for the chemisorption location of the APTS molecule are considered on the hydroxylated Si(001)-(2 x 2) surface: (i) an above-pedestal position (intra-row) between adjacent Si dimers and (ii) an above-hollow position. The first case is found to be energetically more favorable than the latter by 1.04 eV. The electronic band structure of this site has been compared with that of the bare Si(001)-(2 x 2) surface. It is observed that the chemisorption of APTS has considerably changed the electronic structure of the Si(001)-(2 x 2) surface

An ab initio study of 3-aminopropyltrimethoxysilane molecule on Si(111)-(root 3 x root 3) surface

The chemisorption and reaction of 3-aminopropyltrimethoxysilane (APTS) molecule on the Si(111)-(root 3 x root 3) surface are investigated by first principles density-functional calculations within the generalized gradient approximation. Before studying the chemisorption of APTS molecule on the surface, we have firstly put three-OH groups on the silicon surface, but considering six different locations for H and O atoms. Upon their relaxations, model 11, which is assumed to be crosswise for initial orientation of -OH groups, was found to be energetically more favorable than the others. In model 11, after the relaxation, its conformation was transformed to skewed structure due to the repulsive forces between -OH groups. Isolated APTS molecule was also investigated in order to obtain its most stable molecular geometry, for which the HOMO-LUMO gap was found to be 4.41 eV. In addition to these, after the energetically most favorable hydroxylated Si(111) surface was calculated, APTS molecule was chemisorbed on the surface by means of liberating its methoxy groups. In our model for the binding of APTS molecule on the Si(111) surface, the silicon atom in the APTS forms three bonds to hydroxyl groups at the surface

Association between PTEN IVS4 polymorphism and development of colorectal cancer in a Turkish population

Background: Phosphatase and tensin homolog (PTEN) is one of the most frequently mutated suppressor genes in human cancers. However, there are no data about the role of PTEN IVS4 polymorphism in development of colorectal cancer (CRC). The authors aimed to determine the role of PTEN IVS4 variants in the etiology of CRC

Increased Gastric Cancer Risk with PTEN IVS4 Polymorphism in a Turkish Population

We aimed to investigate the association of the phosphatase and tensin homolog (PTEN) IVS4 polymorphism with a gastric cancer (GC) risk in the Turkish population. A hospital-based case-control study was conducted in 93 patients with GC, and 113 healthy controls. The PTEN IVS4 (rs no: 3830675) polymorphism was determined by using polymerase chain reaction-restriction fragment length polymorphism analysis. The PTEN IVS4 (-/-) genotype exhibited a significantly elevated risk for GC compared to controls (p 0.05). In conclusion, the PTEN IVS4 polymorphism might contribute to the development of GC in a Turkish population. Further studies, including comparison of the PTEN IVS4 polymorphism with plasma and tissue expressions of PTEN in larger study size groups will provide a further assessment of the PTEN IVS4 polymorphism in GC patients