Preparation of polymer/LDH nanocomposite by UV-initiated photopolymerization of acrylate through photoinitiator-modified LDH precursor

The exfoliated polymer/layered double hydroxide (LDH) nanocomposite by UV-initiated photopolymerization of acrylate systems through an Irgacure 2959-modified LDH precursor (LDH-2959) as a photoinitiator complex was prepared. The LDH-2959 was obtained by the esterification of 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959) with thioglycolic acid, following by the addition reaction with 3-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), finally intercalation into the sodium dodecyl sulfate-modified LDH. For comparison, the intercalated polymer/LDH nanocomposite was obtained with additive Irgacure 2959 addition. From the X-ray diffraction (XRD) measurements and HR-TEM observations, the LDH lost the ordered stacking-structure and well dispersed in the polymer matrix at 5 wt% LDH-2959 loading. The glass transition temperature of UV-cured exfoliated nanocomposites increased to 64 °C from 55 °C of pure polymer without LDH addition. The tensile strength was improved from 10.1 MPa to 25.2 MPa, as well the Persoz hardness enhanced greatly, while the elongation at break remained an acceptable level.     

Non-cytotoxic organic–inorganic hybrid bioscaffolds: An efficient bedding for rapid growth of bone-like apatite and cell proliferation

Synthesis and characterization of organic–inorganic macroporous hybrid scaffolds were investigated. The materials were prepared by combining 2-hydroxyethylmethacrylate (HEMA) and triethoxyvinylsilane (TEVS) chemically modified by Ca^2 + and PO₄^3 ? ions via sol–gel route. In this study we have constructed a sugar-based cracks-free three-dimensional (3D) network with interconnected porous architecture within the range of 150–300 μm and rough topography. The obtained results revealed that both topography and composition of prepared materials allow rapid growth of the bone-like apatite (HAp) layer on their surface after soaking in biological medium. Preliminary studies have shown that hybrids covered by HAp are non-cytotoxic and allow cell proliferation that make them a promising scaffolds in the field of bone regenerative medicine. The materials were mainly characterized by powder X-ray diffraction analysis (PXRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy–energy-dispersive spectroscopy (SEM–EDS) and transmission electron microscopy–energy-dispersive spectroscopy (TEM–EDS).     

Synthesis and in vitro release study of ibuprofen-loaded gelatin graft copolymer nanoparticles

Objective: This work deals with the preparation, characterization and in vitro release study of IBU-loaded gel graft copolymer nanoparticles.

Method: Gelatin (Gel) graft copolymer nanoparticles were prepared using styrene (Sty) and/or 2-hydroxyethyl methacrylate (HEMA) monomers in the presence of potassium persulfate and glutaraldehyde as an initiator and cross-linker, respectively. The prepared nanoparticles as sustained release drug carriers were investigated using the nonsteriodal anti-inflammatory model drug, ibuprofen (IBU).

Results: The prepared nanoparticles as sustained release drug carriers were investigated using the nonsteriodal anti-inflammatory model drug, IBU. The prepared Gel/HEMA and Gel/Sty nanoparticles exhibited particles size ranging from 15 to 17?nm and from 0.42 to 5?mm, respectively. The dissolution of IBU in phosphate buffer, pH 7.4, at 37°C from the prepared nanoparticles was evaluated using UV spectroscopy. In addition, the prepared nanoparticles were characterized using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), transmitting electron microscope (TEM) and zeta potential/particle size analyzer. In vitro dissolution study showed that the dissolution rates of the crosslinked nanoparticles were retarded relative to the uncrosslinked ones. Moreover, the released amount constantly decreases with increasing gluteraldehyde content in the gel nanoparticles.

Conclusion: Crosslinked gel-based graft copolymers exhibited slow IBU release within six hours. Furthermore, results from different characterization techniques such as TEM, particles size and zeta potential measurements confirmed the formation of pH-responsive gel-graft copolymer nanoparticles.     

In vitro release profile of anti-ulcer drug rabeprazole from biocompatible psyllium-PVA hydrogels

The present article discusses the synthesis, characterization and haemocompatibility behaviour of the psyllium-PVA hydrogels prepared by chemical method in the presence of N,N′-methylenebisacrylamide. These hydrogels have been characterized by Fourier Transform infrared spectroscopy, thermo gravimetric analysis, swelling and drug release studies. The release of model drug rabeprazole sodium from the drug loaded hydrogels occurred through non-Fickian diffusion mechanism. Psyllium itself acts as anti-ulcer agent and release of rabeprazole from the drug loaded hydrogels may enhance the curing potential of the drug delivery device. The haemocompatibility was evaluated by studying the blood interactions with hydrogels with reference to thrombogenicity and haemolytic potential. Thrombogenicity results indicate that hydrogels are non-thrombogenic as the weight of clot formed and thrombus percentage for hydrogels was less than the positive control. The haemolytic index has been observed <5%. These observations indicate that these hydrogels are haemo-compatible and hence could be used for oral administration of antiulcer drugs.     

Slow release of ciprofloxacin from double potential drug delivery system

Psyllium polysaccharide is a bulk laxative and has been used for the treatment of constipation which is responsible for the diverticulitis. Ciprofloxacin is an antibiotic used for the microorganism infested in the diverticula. Hence, the functionalization of psyllium with polyvinyl alcohol (PVA) and poly(acrylamide) [poly(AAm)] will develop the drug delivery system (DDS) with potential for dual action for the treatment of diverticulitis, that is, by treating the constipation due to laxative action of psyllium and release of ciprofloxacin from DDS in controlled manner. The optimum conditions for the synthesis of hydrogels have been obtained as 42.21 × 10⁻² mol/L of AAm, 3% (w/v) of PVA, 32.43 × 10⁻³ mol/L of N,N′-methylenebisacrylamide (NN-MBA), 17.53 × 10⁻³ mol/L ammonium persulfate, and 1 g of psyllium. The characterization of the hydrogels has been carried out by SEMs, EDAX, FTIR, and swelling studies. Swelling and drug release studies have also been carried out to determine the mechanism of swelling of hydrogels and drug release from the drug loaded hydrogels. The release of the drug from the hydrogels occurred through Fickian diffusion mechanism in pH 2.2 and pH 7.4 buffer.     

The Effect of a Rate Controlling Membrane on Release from Polyhema Hydrogels

The possibility of laminating a non-permeable, perforated membrane onto a polymer matrix providing zero-order drug release kinetics has been reported. The work we have undertaken involves an assessment of the suitability of poly(2-hydroxyethylmethacrylate) (polyHEMA) as the matrix in such a system. PolyHEMA hydrogels were prepared by the radiation polymerization of HEMA monomer solutions of different initial water contents. Membranes were laminated during the polymerization process. In Vitro release rates of substituted benzoic acids from laminates were determined.     

组织工程用PEGDA水凝胶材料低温等离子体接枝聚合

采用自由基聚合法合成了聚乙二醇双丙烯酸酯(PEGDA)/甲基丙烯酸β-羟乙酯(HEMA)共聚物水凝胶,材料表面在非反应性气体氩气气氛下进行等离子体表面处理,并在紫外光辐照条件下进行丙烯酰胺接枝共聚。红外谱图证明PEGDA/HEMA共聚物水凝胶上接枝了酰胺基团,材料的亲水性提高,等离子体表面处理后,材料表面形成含氧基团,氮原子含量增加。     

Macroporous hydrogels based on 2-hydroxyethyl methacrylate. Part 4: Growth of rat bone marrow stromal cells in three-dimensional hydrogels with positive and negative surface charges and in polyelectrolyte complexes

The growth of bone marrow stromal cells was assessed in vitro in macroporous hydrogels based on 2-hydro- xyethyl methacrylate (HEMA) copolymers with different electric charges. Copolymers of HEMA with sodium methacrylate (MA⁻) carried a negative electric charge, copolymers of HEMA with [2-(methacryloyloxy)ethyl] trimethylammonium chloride (MOETA⁻) carried a positive electric charge and terpolymers of HEMA, MA⁻ and MOETA⁺ carried both, positive and negative electric charges. The charges in the polyelectrolyte complexes were shielded by counter-ions. The hydrogels had similar porosities, based on a comparison of their diffusion parameters for small cations as measured by the real-time tetramethylammonium iontophoretic method of diffusion analysis. The cell growth was studied in the peripheral and central regions of the hydrogels at 2 hours and 2, 7, 14 and 28 days after cell seeding. Image analysis revealed the highest cellular density in the HEMA-MOETA⁺ copolymers; most of the cells were present in the peripheral region of the hydrogels. A lower density of cells but no difference between the peripheral and central regions was observed in the HEMA-MA⁻ copolymers and in polyelectrolyte complexes. This study showed that positively charged functional groups promote the adhesion of cells.     

Surface modification of nanophase hydroxyapatite with chitosan

Nanophase hydroxyapatite (HAp) particles were aged in 0–2.5 wt.% chitosan acetate solutions for 30 days to evaluate the influence of chitosan on HAp surface chemistry. The HAp characterization results from Fourier transform infra-red spectroscopy (FTIR), thermal gravimetric analysis (TGA), Carbon–Hydrogen–Nitrogen (CHN) analysis, and BET N₂ adsorption revealed measurable changes in the HAp surface chemistry after aging in the chitosan acetate solutions. The TGA mass loss exhibited by HAp increased from 3.3–6.5 mass% as the chitosan acetate gel concentration increased from 0–2.5 mass%. The CHN analysis revealed an increase in C and H contents with increasing chitosan acetate concentration while the N concentration remained relatively constant (0.30–0.32 mass%). Chitosan interactions with HAp caused an increase in specific surface area from 85 m²/g up to 160 m²/g for HAp aged in 1.5 mass% chitosan acetate solution (HAp[1.5]). Chitosan exhibits strong adsorption interactions with HAp and enhances colloid stability for processing of chitosan/hydroxyapatite nanocomposites.     

Release of BSA from porous matrices constituted of alginate–Ca and PNIPAAm-interpenetrated networks

The synthesis of thermosensitive Interpenetrating Polymer Network (IPN) hydrogels and the release of Bovine Serum Albumin (BSA) from the hydrogels were reported. The hydrogels, constituted of poly(N-isopropyl acrylamide) PNIPAAm network interpenetrated in alginate–Ca²⁺ network, were synthesized in a two-stepped process. In the first step, PNIPAAm network was synthesized from an aqueous solution containing N-isopropyl acrylamide (NIPAAm) monomers and N,N′-methylene-bis-acrylamide (MBAAm) co-monomers, and sodium alginate (SA) (1 or 2% w/v). The concentration of NIPAAm monomers in the hydrogel-forming solution was always 2.5, 5.0 or 10.0% (w/v). In the second step, alginate–Ca²⁺ networks were formed by immersion of the membrane, obtained on the first step, in a 1.0% (w/v) aqueous calcium chloride. The IPN hydrogels were characterized as a function of temperature (from 25 to 45 °C) through the following measurements: drop water contact angle (DWCA), compression elastic modulus (E) and cross-linking density (ν_e). The morphology was investigated using scanning electronic microscopy (SEM). In vitro release of BSA from the hydrogels was monitored by UV–Vis spectroscopy at 22 °C and 37 °C. DWCA results showed a decrease in the hydrogel hydrophilicity when the temperature and/or the PNIPAAm amount on hydrogels were increased. PNIPAAm-loader hydrogels are more compacted and presented elevated rigidity, mainly above 35 °C. This trend was attributed to the collapsing of PNIPAAm chains as the hydrogels were warmed above its Lower Critical Solution Temperature (LCST), which in aqueous solution is ca. 32–33 °C. The amount of BSA released from the alginate–Ca²⁺/PNIPAAm hydrogels changes inversely to both amount of PNIPAAm and temperature. The transport of BSA from the hydrogels was evaluated through a conventional model. In the lesser-compacted hydrogels the release occurs mostly by diffusion. In the more compacted ones the chain relaxation contributes to the BSA release. Thus, the alginate–Ca²⁺/PNIPAAm IPN-typed matrixes may be considered as smart hydrogels for the release of BSA, because the amount and rate of BSA released may be tailored by both the NIPAAm concentration in the hydrogel-forming solution and the control of temperature of hydrogel.     

The Effect of a Rate Controlling Membrane on Release from Polyhema Hydrogels

The possibility of laminating a non-permeable, perforated membrane onto a polymer matrix providing zero-order drug release kinetics has been reported. The work we have undertaken involves an assessment of the suitability of poly(2-hydroxyethylmethacrylate) (polyHEMA) as the matrix in such a system. PolyHEMA hydrogels were prepared by the radiation polymerization of HEMA monomer solutions of different initial water contents. Membranes were laminated during the polymerization process. In Vitro release rates of substituted benzoic acids from laminates were determined.     

Development of porous HAp and β-TCP scaffolds by starch consolidation with foaming method and drug-chitosan bilayered scaffold based drug delivery system

The inability to maintain high concentrations of antibiotic at the site of infection for an extended period of time along with dead space management is still the driving challenge in treatment of osteomyelitis. Porous bioactive ceramics such as hydroxyapatite (HAp) and beta-tri calcium phosphate (β-TCP) were some of the alternatives to be used as local drug delivery system. However, high porosity and high interconnectivity of pores in the scaffolds play a pivotal role in the drug release and bone resorption. Ceftriaxone is a cephalosporin that has lost its clinical popularity. But has recently been reported to exhibit better bactericidal activity in vitro and reduced probability of resistance development, in combination with sulbactam, a β-lactamase inhibitor. In this article, a novel approach of forming HAp and pure β-TCP based porous scaffolds by applying together starch consolidation with foaming method was used. For the purpose, pure HAp and β-TCP were prepared in the laboratory and after thorough characterization (including XRD, FTIR, particle size distribution, etc.) the powders were used for scaffold fabrication. The ability of these scaffolds to release drugs suitably for osteomyelitis was studied in vitro. The results of the study indicated that HAp exhibited better drug release profile than β-TCP when drug was used alone indicating the high influence of the carrier material. However, this restriction got relaxed when a bilayered scaffold was formed using chitosan along with the drug. SEM studies along with EDAX on the drug-chitosan bilayered scaffold showed closest apposition of this combination to the calcium phosphate surface.     

等离子改性条件对PEGDA/HEMA凝胶亲水性及表面能的影响

采用氩等离子对聚乙二醇双丙烯酸酯(PEGDA)/甲基丙烯酸-2-羟基乙酯(HEMA)共聚物凝胶进行表面改性,对膜材料进行了光电子能谱(XPS)分析,并讨论了等离子处理时间及功率对凝胶亲水性及表面能的影响。研究结果表明,经等离子处理后凝胶表面引入了含氧极性基团,氧的含量从未处理的23%增加到26%,使材料亲水性得到改善;由于引入极性基团,材料的表面能随等离子处理时间和功率的增加而增加,从未处理前的45.9 mJ/m2增加到72.5 mJ/m2,极性力分量γPs随等离子体处理功率和时间的变化规律与表面能γs基本一致。     

Hyaluronic acid hydrogels incorporating platelet lysate enhance human pulp cell proliferation and differentiation

The restoration of dentine-pulp complex remains a challenge for dentists; nonetheless, it has been poorly addressed. An ideal system should modulate the host response, as well as enable the recruitment, proliferation and differentiation of relevant progenitor cells. Herein was proposed a photocrosslinkable hydrogel system based on hyaluronic acid (HA) and platelet lysate (PL). PL is a cocktail of growth factors (GFs) and cytokines involved in wound healing orchestration, obtained by the cryogenic processing of platelet concentrates, and was expected to provide the HA hydrogels specific biochemical cues to enhance pulp cells’ recruitment, proliferation and differentiation. Stable HA hydrogels incorporating PL (HAPL) were prepared after photocrosslinking of methacrylated HA (Met-HA) previously dissolved in PL, triggered by the Ultra Violet activated photoinitiator Irgacure 2959. Both the HAPL and plain HA hydrogels were shown to be able to recruit cells from a cell monolayer of human dental pulp stem cells (hDPSCs) isolated from permanent teeth. The hDPCs were also seeded directly over the hydrogels (5?×?10⁴ cells/hydrogel) and cultured in osteogenic conditions. Cell metabolism and DNA quantification were higher, in all time-points, for PL supplemented hydrogels (p?<?0,05). Alkaline phosphatase (ALPL) activity and calcium quantification peaks were observed for the HAPL group at 21 days (p?<?0,05). The gene expression for ALPL and COLIA1 was up-regulated at 21 days to HAPL, compared with HA group (p?<?0,05). Within the same time point, the gene expression for RUNX2 did not differ between the groups. Overall, data demonstrated that the HA hydrogels incorporating PL increased the cellular metabolism and stimulate the mineralized matrix deposition by hDPSCs, providing clear evidence of the potential of the proposed system for the repair of damaged pulp/dentin tissue and endodontics regeneration.     

Poly (vinyl alcohol) hydrogels for pH dependent colon targeted drug delivery

Oral drug administration is convenient with pH dependent drug delivery system since the drug has to pass through different pH environments in gastro intestinal (GI) tract. The pH dependent swelling/shrinking behavior of hydrogel drug carrier controls the drug release without affecting the function of drug. pH dependent hydrogels of poly (vinyl alcohol) (PVA) were prepared by cross linking with maleic acid (MA). The hydrogels were characterized by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, DSC, porosimetry, SEM, TEM, biocompatibility study and by measuring their swelling behavior in water, simulated gastric fluid (SGF) and intestinal fluid (SIF). Swelling of the hydrogels was found to be highest in SIF (pH: 7.5) and lowest in SGF (pH: 1.2) resembling that required in colon targeted drug delivery systems. Since the swelling behavior of the gel is pH dependent, these hydrogels were studied for colon targeted drug delivery in an in-vitro set-up resembling the condition of GI tract. The ratio of PVA and MA in the hydrogel was varied to study the effect on the drug diffusion rate. For drug delivery study, vitamin B₁₂ and salicylic acid were used as model drugs. The hydrogel, loaded with model drugs vitamin B₁₂ and salicylic acid also demonstrated colon specific drug release with a relatively higher drug release in SIF (pH: 7.5) than that in SGF (pH: 1.2).     

Stimuli-responsive bacterial cellulose-g-poly(acrylic acid-co-acrylamide) hydrogels for oral controlled release drug delivery

This study evaluated the potential of stimuli-responsive bacterial cellulose-g-poly(acrylic acid-co-acrylamide) hydrogels as oral controlled-release drug delivery carriers. Hydrogels were synthesized by graft copolymerization of the monomers onto bacterial cellulose (BC) fibers by using a microwave irradiation technique. The hydrogels were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). FT-IR spectroscopy confirmed the grafting. XRD showed that the crystallinity of BC was reduced by grafting, whereas an increase in the thermal stability profile was observed in TGA. SEM showed that the hydrogels exhibited a highly porous morphology, which is suitable for drug loading. The hydrogels demonstrated a pH-responsive swelling behavior, with decreased swelling in acidic media, which increased with increase in pH of the media, reaching maximum swelling at pH 7. The release profile of the hydrogels was investigated in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). The hydrogels showed lesser release in SGF than in SIF, suggesting that hydrogels may be suitable drug carriers for oral controlled release of drug delivery in the lower gastrointestinal tract.     

Laser‐Raman and Nuclear Magnetic Resonance (NMR) studies on plasma‐sprayed hydroxylapatite coatings: Influence of bioinert bond coats on phase composition and resorption kinetics in simulated body fluid

The structure and phase composition of HAp coatings deposited onto Ti6Al4V coupons (50x20x2mm) by atmospheric plasma spraying (APS) were studied by laser‐Raman spectroscopy, ³¹P‐ and ¹H‐MAS‐NMR and 2D‐³¹P/¹H HETCOR‐CP‐NMR spectroscopy, and XRD with Rietveld refinement. The samples investigated comprised APS HAp coatings with and without a TiO₂ bond coat as well as coatings incubated for different lengths of time (up to 12 weeks) in simulated body fluid (SBF) under physiological conditions. In APS coatings the presence of a bond coat increased the proportion of well‐ordered crystalline HAp at the expense of distorted apatite‐like structures such as oxyHAp and oxyapatite, and thermal decomposition products such as tricalcium phosphate (TCP) and tetracalcium phosphate (TTCP), and also decreased the amount of amorphous calcium phosphate (ACP). Incubation in SBF further advanced the proportion of crystalline HAp since the disordered structures, the thermal decomposition products, and ACP exhibit substantially higher solubility.     

Synthesis and characterization of hydroxyapatite–bacterial cellulose nanocomposites

Biocomposites consisting of hydroxyapatite (HAp) and natural polymers such as collagen, chitosan, chitin, and gelatin have been extensively investigated. However, studies on the combination of HAp with bacterial cellulose (BC) have not been conducted yet. In this work, our latest results concerning the biomimetic synthesis and characterization of HAp-BC nanocomposites with a 3-dimensional (3-D) network are reported. The present research focuses on characterizing the structure of this novel class of nanocomposites. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Fourier-transformed infrared spectroscopy (FTIR) were employed to characterize the HAp-BC nanocomposites. It is found that HAp crystals are formed when the phosphorylated and CaCl₂-treated BC fibers are soaked in a 1.5 simulated body fluid (SBF). XRD reveals that the crystallite sizes of the HAp crystals are nano-sized and their crystallinities are low. The FTIR results show that the HAp crystals are partially substituted with carbonate, resembling natural bones. The nanocomposites containing HAp with structural features close to those of biological apatites are attractive for applications as artificial bones and scaffolds for tissue engineering.     

Poly (vinyl alcohol) hydrogels for pH dependent colon targeted drug delivery

Oral drug administration is convenient with pH dependent drug delivery system since the drug has to pass through different pH environments in gastro intestinal (GI) tract. The pH dependent swelling/shrinking behavior of hydrogel drug carrier controls the drug release without affecting the function of drug. pH dependent hydrogels of poly (vinyl alcohol) (PVA) were prepared by cross linking with maleic acid (MA). The hydrogels were characterized by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, DSC, porosimetry, SEM, TEM, biocompatibility study and by measuring their swelling behavior in water, simulated gastric fluid (SGF) and intestinal fluid (SIF). Swelling of the hydrogels was found to be highest in SIF (pH: 7.5) and lowest in SGF (pH: 1.2) resembling that required in colon targeted drug delivery systems. Since the swelling behavior of the gel is pH dependent, these hydrogels were studied for colon targeted drug delivery in an in-vitro set-up resembling the condition of GI tract. The ratio of PVA and MA in the hydrogel was varied to study the effect on the drug diffusion rate. For drug delivery study, vitamin B12 and salicylic acid were used as model drugs. The hydrogel, loaded with model drugs vitamin B12 and salicylic acid also demonstrated colon specific drug release with a relatively higher drug release in SIF (pH: 7.5) than that in SGF (pH: 1.2).     

Swelling and Aspirin Release Study: Cross-Linked pH-Sensitive Vinyl Acetate-co-Acrylic Acid (VAC-co-AA) Hydrogels

The objective of this work was to develop new pH-sensitive hydrogels to deliver gastric mucosal irritating drugs to the lower part of the gastrointestinal tract. For this purpose, cross-linked vinyl acetate-co-acrylic acid (VAC-co-AA) hydrogels were synthesized by using N, N, methylene bisacrylamide (MBAAm) as a cross-linking agent. Different ratios of 90:10, 70:30, 50:50, 30:70, and 10:90 of VAC-co-AA were synthesized. All of the compositions were cross-linked using 0.15, 0.30, 0.45, and 0.60 mol percent MBAAm. Swelling and aspirin release were studied for 8 hour period. The drug release data were fitted into various kinetic models like the zero-order, first-order, Higuchi, and Peppas. Hydrogels were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. In addition to the above, these hydrogels were loaded with 2%, 8% and 14% w/v aspirin solutions, keeping the monomeric composition and degree of cross-linking constant. In conclusion, it can be said that aspirin can be successfully incorporated into cross-linked VAC/AA hydrogels and its swelling and drug release can be modulated by changing the mole fraction of the acid component in the gels.