Preparation of hydroxyapatite-gelatin nanocomposite

A nanocomposite of gelatin[GEL]-hydroxyapatite[HAp] was prepared using the biomimetic process. The hydroxyapatite nanocrystals were precipitated in aqueous solution of gelatin at pH 8 and 38 degrees C. The chemical bonding between calcium ions of HAp and carboxyl ions of GEL molecules induced a red-shift of the 1339 cm(-1) band of GEL in FT-IR analysis. TEM images and electron diffraction patterns for the nanocomposite strongly indicate the self-organization of HAp nanocrystals along the GEL fibrils. Electron diffraction for the nanocomposites showed a strong preferred orientation of the (002) plane in HAp nanocrystals. The development of HAp nanocrystals in an aqueous GEL solution was highly influenced by the concentration ratio of GEL to HAp. A higher concentration of GEL induced the formation of tiny crystallites (4 nm x 9 nm size), while a lower concentration of GEL contributed to the development of bigger crystallites (30 nm x 70 nm size). From DT/TGA data, the HAp-GEL nanocomposite showed typically three exothermic temperatures. The increase in decomposition temperatures indicates the formation of a primary chemical bond between HAp and GEL. The higher concentration of GEL supplies abundant reaction sites containing groups such as carboxyl, which can bind with calcium ions. The abundant supply of reaction sites leads to a very large number of HAp nuclei. However, the formation of a large number of nuclei depletes the concentration of calcium ions that available for growth to the extent that the nuclei cannot grow very large. This in turn will lead to the creation of a large number of tiny nanocrystals at this higher GEL concentration.

Study on physical properties and nerve cell affinity of composite films from chitosan and gelatin solutions

A series of chitosan-gelatin composite films was prepared by varying the ratio of constituents. FT-IR and X-ray analysis showed good compatibility between these two biopolymers. Differential scanning calorimetry (DSC) analysis indicated that the water take-up of chitosan film increased when blended with gelatin. Composite film exhibited a lower Young's modulus and a higher percentage of elongation-at-break compared with chitosan film, especially in wet state. All composite films were hydrophilic materials with water contact angles ranging from 55 degrees to 65 degrees. The results obtained from ELISA indicated the adsorption amount of fibronectin on composite films was much higher than on chitosan film. PC12 cells culture was used to evaluate the nerve cell affinity of materials. The cells cultured on the composite film with 60wt% gelatin differentiated more rapidly and extended longer neurites than on chitosan film. The results suggest that the soft and elastic complex of chitosan and gelatin, which has better nerve cell affinity compared to chitosan, is a promising candidate biomaterial for nerve regeneration.

Enzyme-catalyzed gel formation of gelatin and chitosan: potential for in situ applications

We compared the ability of two enzymes to catalyze the formation of gels from solutions of gelatin and chitosan. A microbial transglutaminase, currently under investigation for food applications, was observed to catalyze the formation of strong and permanent gels from gelatin solutions. Chitosan was not required for transglutaminase-catalyzed gel formation, although gel formation was faster, and the resulting gels were stronger if reactions were performed in the presence of this polysaccharide. Consistent with transglutaminase's ability to covalently crosslink proteins, we observed that the transglutaminase-catalyzed gelatin-chitosan gels lost the ability to undergo thermally reversible transitions (i.e. sol-gel transitions) characteristic of gelatin. Mushroom tyrosinase was also observed to catalyze gel formation for gelatin-chitosan blends. In contrast to transglutaminase, tyrosinase-catalyzed reactions did not lead to gel formation unless chitosan was present (i.e. chitosan is required for tyrosinase-catalyzed gel formation). Tyrosinase-catalyzed gelatin-chitosan gels were observed to be considerably weaker than transglutaminase-catalyzed gels. Tyrosinase-catalyzed gels were strengthened by cooling below gelatin's gel-point, which suggests that gelatin's ability to undergo a collagen-like coil-to-helix transition is unaffected by tyrosinase-catalyzed reactions. Further, tyrosinase-catalyzed gelatin-chitosan gels were transient as their strength (i.e. elastic modulus) peaked at about 5h after which the gels broke spontaneously over the course of 2 days. The strength of both transglutaminase-catalyzed and tyrosinase-catalyzed gels could be adjusted by altering the gelatin and chitosan compositions. Potential applications of these gels for in situ applications are discussed.

Preparation and evaluation of drug-loaded gelatin nanoparticles for topical ophthalmic use

Gelatin nanoparticles encapsulating pilocarpine HCl or hydrocortisone as model drugs were produced using a desolvation method. The influence of a number of preparation parameters on the particle properties was investigated. For the pilocarpine HCl-loaded spheres, an influence of the pH during particle preparation on the size was observed. Slightly negative zeta potential values were measured for all samples. In the case of pilocarpine HCl-loaded spheres, no influence of the gelatin type or the pH level was observed, which could be attributed to the shielding effect of ions present in the dispersion medium. When hydrocortisone was entrapped, a difference in zeta potential value between gelatin type A and gelatin type B particles was measured. A high pilocarpine HCl entrapment was established. Hydrocortisone was complexed with cyclodextrins in order to increase its aqueous solubility. The drug encapsulation was lower than in the case of pilocarpine HCl, but still amounted to approximately 30-40%. Compared to the aqueous drug solutions, a sustained release for both drugs was observed. The release kinetics of pilocarpine HCl are close to zero order, and no significant differences were measured between the various preparations. In the case of hydrocortisone, the release data suggests a difference in release rate depending on the type of cyclodextrin employed.

Intervertebral Disc Regeneration Using Platelet-Rich Plasma and Biodegradable Gelatin Hydrogel Microspheres

This study evaluated the regenerative effects of platelet-rich plasma (PRP) for the degenerated intervertebral disc (IVD) in vivo. After induction of IVD degeneration in rabbits, we prepared PRP by centrifuging blood obtained from these rabbits. These PRP were injected into the nucleus pulposus (NP) of the degenerated IVDs after impregnation into gelatin hydrogel microspheres that can immobilize PRP growth factors physiochemically and release them in a sustained manner with the degradation of the microspheres. As controls, microspheres impregnated with phosphate-buffered saline (PBS) and PRP without microspheres were similarly injected. Histologically, notable progress in IVD degeneration with time courses was observed in the PBS control, PRP-only, and sham groups. In contrast, progress was remarkably suppressed over the 8-week period in the PRP group. Moreover, in immunohistochemistry, intense immunostaining for proteoglycan in the NP and inner layer of the annulus fibrosus was observed 8 weeks after administration of PRP-impregnated microspheres. Almost all microspheres were indistinct 8 weeks after the injection, and there were no apparent side effects in this study. Our results suggest that the combined administration of PRP and gelatin hydrogel microspheres into the IVD may be a promising therapeutic modality for IVD degeneration.

Preparation and in vitro characterization of cross-linked collagen-gelatin hydrogel using EDC/NHS for corneal tissue engineering applications

Corneal disease is considered as the second leading cause of vision loss and keratoplasty is known as an effective treatment for it. However, the tissue engineered corneal substitutes are promising tools in experimental in vivo repair of cornea. Selecting appropriate cell sources and scaffolds are two important concerns in corneal tissue engineering. The object of this study was to investigate biocompatibility and physical properties of the bio-engineered cornea, fabricated from type-I collagen (COL) and gelatin (Gel). Two gelatin based hydrogels cross-linked with EDC/NHS were fabricated, and their physicochemical properties such as equilibrium water content, enzymatic degradation, mechanical properties, rheological, contact angle and optical properties as well as their ability to support human bone-marrow mesenchymal stem cells (hBM-MSCs) survival were characterized. The equilibrium water content and enzymatic degradation of these hydrogels can be easily controlled by adding COL. Our findings suggest that incorporation of COL-I increases optical properties, hydrophilicity, stiffness and Young's modulus. The viability of hBM-MSCs cultured in Gel and Gel: COL was assessed via CCK-8 assay. Also, the morphology of the hBM-MSCs on the top of Gel and Gel: COL hydrogels were characterized by phase-contrast microscopy. This biocompatible hydrogel may promise to be used as artificial corneal substitutes.

Conformational change of hydroxyapatite/gelatin nanocomposite by glutaraldehyde

The hydroxyapatite (HAp)/gelatin (GEL) nanocomposite was prepared through the coprecipitation and then cross-linked by using glutaraldehyde (GA). From FT-IR measurement the spectral features for amide bands and phosphate bands were severely modified by the cross-linkage and the organic content increased with the degree of cross-linkage. From Transmission Electron Microscopy (TEM) and electron diffraction analyses we could confirm the preferentially directional growth of needle-like HAp particles, which were embedded in GEL by the mineralization. Also we could observe worm-like stria patterns of contrast, which were revealed by the mineralization on the individual GEL fibrils. Moiré images were observed in a highly cross-linked HAp/GEL nanocomposite sample and we think the cross-linkage induced the assembly of unordered individual fibrils along the preferential direction.

Mechanical behaviour and biocompatibility of poly(1-vinyl-2-pyrrolidinone)-gelatin IPN hydrogels

IPN hydrogels based on poly(1-vinyl-2-pyrrolidinone) and gelatin were obtained by casting of aqueous solution using potassium persulphate and glutaraldehyde as respective crosslinking agents. Studies of swelling and mechanical behaviour showed that the samples of different composition can incorporate high content of water and still exhibit high compression strength. The composition has influence at the global crosslinking density what affects the mechanical performance. In vitro biocompatibility and hemocompatibility were also investigated. The materials do not interfere on the cellular functions and neither induce platelet adhesion. From this preliminary evaluation, it is possible to conclude that these hydrogels have potential for applications in the biomedical field.

Polymeric Enhancers of Mucosal Epithelia Permeability: Synthesis, Transepithelial Penetration-Enhancing Properties, Mechanism of Action, Safety Issues

Transmucosal drug administration across nasal, buccal, and ocular mucosae is noninvasive, eliminates hepatic first-pass metabolism and harsh environmental conditions, allows rapid onset, and further, mucosal surfaces are readily accessible. Generally, however, hydrophilic drugs, such as peptides and proteins, are poorly permeable across the epithelium, which results in insufficient bioavailability. Therefore, reversible modifications of epithelial barrier structure by permeation enhancers are required. Low molecular weight enhancers generally have physicochemical characteristics favoring their own absorption, whereas polymeric enhancers are not absorbed, and this minimizes the risk of systemic toxicity. The above considerations have warranted the present survey of the studies on polymeric transmucosal penetration-enhancers that have appeared in the literature during the last decade. Studies on intestinal permeation enhancers are also reviewed as they give information on the mechanism of action and safety of polymers. The synthesis and characterization of polymers, their effectiveness in enhancing the absorption of different drugs across different epithelium types, their mechanism of action and structure-efficacy relationship, and the relevant safety issues are reviewed. The active polymers are classified into: polycations (chitosan and its quaternary ammonium derivatives, poly-L-arginine (poly-L-Arg), aminated gelatin), polyanions (N-carboxymethyl chitosan, poly(acrylic acid)), and thiolated polymers (carboxymethyl cellulose-cysteine, polycarbophil (PCP)-cysteine, chitosan-thiobutylamidine, chitosan-thioglycolic acid, chitosan-glutathione conjugates).

A novel surgical glue composed of gelatin and N-hydroxysuccinimide activated poly(L-glutamic acid): Part 1. Synthesis of activated poly(L-glutamic acid) and its gelation with gelatin

Although fibrin glue has been widely used as a surgical adhesive, its components, fibrinogen and thrombin, obtained from human blood are not completely free from the risk of virus infection due to acquired immune deficiency and hepatitis. Recently, we have reported that a polymer pair composed of gelatin and poly(L-glutamic acid) (PLGA) promptly forms a gel and can firmly bond to soft tissues when crosslinked with the aid of water-soluble carbodiimide (WSC). The present study was undertaken to design a new PLGA-gelatin glue without using WSC. Two kinds of PLGA with molecular weights of 71 and 22 kDa were employed to prepare N-hydroxysuccinimide (NHS) activated derivatives. The NHS-activated PLGA could be synthesized at high yields and was found to be stable for an extended time without losing the ability to crosslink with gelatin when stored under a dry-cold condition. This NHS-activated PLGA could spontaneously form a gel with gelatin in an aqueous solution within a short time, comparable to a commercial fibrin glue, when gelation was allowed to proceed at pH 8.3. The NHS-activated PLGA prepared from PLGA with the molecular weight of 22 kDa could be readily dissolved at high concentrations and its ability to form a gel was maintained for more than 10 min when an acidic 8% NHS-activated PLGA solution was used. The bonding strength of PLGA gelatin glues with natural tissue was higher than that of fibrin glue. These findings strongly suggest that this combination of gelatin and NHS-PLGA is very promising as a surgical adhesive and may possibly replace fibrin glues prepared from human blood components.

Synthesis and characterization of a new interpenetrated poly(2-hydroxyethylmethacrylate)-gelatin composite polymer

Poly(2-hydroxyethylmethacrylate) [poly(HEMA)] is a widely used biomaterial which does not allow cell adhesion and growth on its surface, limiting its use in biomedical applications in which cell cohesion is detrimental. We have prepared a poly(HEMA)-gelatin composite hydrogel using a sequential interpenetrating polymer network technique. The properties of this material were compared with poly(HEMA) freeze-dried sponges in terms of morphology, mechanical properties and biocompatibility. Moreover, in vivo biocompatibility experiments highlighted the occurrence of cellular interactions on the surface of the poly(HEMA)-gelatin interpenetrating polymer network, which are usually absent when unmodified poly(HEMA) hydrogels are implanted in the same host organism. These tests also showed a progressive gelatin degradation from the surface to the bulk of the poly(HEMA)-gelatin specimens during short-term (7 d) implantation. Finally, in vitro tests confirmed an improved ability of this composite to scaffold for the cells.

Gelatin-based biomimetic tissue adhesive. Potential for retinal reattachment

An adhesive that cures under moist/wet conditions could facilitate surgical procedures for retinal reattachment. We are investigating an adhesive that mimics the factor XIIIa-mediated crosslinking of fibrin that occurs in the late stages of the blood coagulation cascade. Specifically, we use gelatin as the structural protein (in place of fibrin), and crosslink gelatin using a calcium-independent microbial transglutaminase (in place of the calcium-dependent transglutaminase factor XIIIa). Injection of gelatin and microbial transglutaminase (mTG) into the vitreous cavity of Sprague Dawley white rats did not elicit structural or cellular damage to the retina as evidenced from histological evaluation 2 weeks post-injection. Qualitative in vitro studies indicate that the gelatin-mTG adhesive binds to bovine retinal tissue under wet conditions. Quantitative lap-shear tests were performed with more robust bovine tissue from the choroid and sclera. The lap-shear strength of the biomimetic gelatin-mTG adhesive was independent of tissue-type and ranged from 15 to 45 kPa, which is comparable to the values reported for other soft-tissue adhesives. These studies suggest that the mTG-crosslinked gelatin may provide a simple, safe, and effective adhesive for ophthalmic applications.

Nitrocinnamate-functionalized gelatin: synthesis and "smart"hydrogel formation via photo-cross-linking

Gelatin having p-nitrocinnamate pendant groups (Gel-NC) was prepared via an efficient one-pot synthesis, yield >87%. (1)H NMR data indicated that 1 mol of gelatin was modified with 18 +/- 6 mol of the photosensitive group. Upon exposure to low-intensity 365 nm UV light and in the absence of photoinitiators or catalysts, Gel-NC cross-linked within minutes into a gelatin-based hydrogel as monitored by UV-vis spectroscopy. The degree of swelling of this biodegradable hydrogel in aqueous solutions responded to changes in Gel-NC concentration levels, the ionic strength of the aqueous solutions, and photo-cross-linking time. Topography changes associated with phase transition resulting from "photocleavage" of the hydrogel network with 254 nm UV light were studied with AFM. Both Gel-NC and its hydrogel expressed low toxicity to human neonatal fibroblast cells. In addition, gelatin-based microgels were prepared via the photo-cross-linking of Gel-NC within inverse micelles.

Synthesis and characterization of gelatin nanoparticles using CDI/NHS as a non-toxic cross-linking system

Gelatin nanoparticles, cross-linked by a mixture of a water soluble carbodiimide (CDI) and N-hydroxysuccinimide (NHS) as a non-toxic cross-linking system, was prepared. The conventional two step desolvation method with acetone as the non-solvent was used. The mean size and size distribution as well as the morphology of the formed nanoparticles were evaluated and compared with those of nanoparticles cross-linked by glutaraldehyde (GA) as the most commonly used cross-linking agent. Furthermore, intrinsic viscosities of the nanoparticles cross-linked by CDI/NHS and GA were measured and compared under various conditions. The results showed the formation of smoother and more homogeneous nanoparticles with smaller size when CDI/NHS used as cross-linking agent under the same synthesis condition. Moreover, nanoparticles encapsulating paracetamol as a model drug were produced by the two different cross-linking agents and were characterized for drug entrapment and loading efficiencies and in vitro drug release. Both drug entrapment and loading efficiencies was higher in the CDI/NHS cross-linked nanoparticles; however, the release kinetics was comparable to that of nanoparticles cross-linked with GA. The differences in the characteristics of CDI/NHS and GA cross-linked nanoparticles were attributed to the different nature of network structures formed by the two cross-linking agents. On the whole, these results suggested that CDI/NHS cross-linked nanoparticles have high potential to be used for drug delivery application in preference to the nanoparticles synthesized by toxic cross-linking agents.

Enzymatic synthesis and antioxidant property of gelatin-catechin conjugates

Gelatin-catechin conjugate was synthesized by the laccase-catalyzed oxidation of catechin in the presence of gelatin. The conjugate had a good scavenging activity against superoxide anion radicals. Moreover, the conjugate showed an amplified inhibition effect on human low density lipoprotein oxidation initiated by 2,2'-azobis(2-amidinopropane)dihydrochloride as a radical generator.

Thiol-ene-based biological/synthetic hybrid biomatrix for 3-D living cell culture

Although various cell encapsulation materials are available commercially for a wide range of potential therapeutic cells, their combined clinical impact remains inconsistent. Synthetic materials such as poly(ethylene glycol) (PEG) hydrogels are mechanically robust and have been extensively explored but lack natural biofunctionality. Naturally derived materials including collagen, fibrin and alginate-chitosan are often labile and mechanically weak. In this paper we report the development of a hybrid biomatrix based on the thiol-ene reaction of PEG diacrylate (PEGdA) and cysteine/PEG-modified gelatin (gel-PEG-Cys). We hypothesized that covalent crosslinking decreases gelatin dissolution thus increasing gelatin resident time within the matrix and the duration of its biofunctionality; at the same time the relative ratio of PEGdA to gel-PEG-Cys in the matrix formulation directly affects hydrogel bulk and local microenvironment properties. Bulk viscoelastic properties were highly dependent on PEGdA concentration and total water content, while gel-PEG-Cys concentration was more critical to swelling profiles. Microviscoelastic properties were related to polymer concentration. The covalently crosslinked gel-PEG-Cys with PEGdA decreased gelatin dissolution out of the matrix and collagenase-mediated degradation. Fibroblasts and keratinocyte increased adhesion density and formed intercellular connections on stiffer hydrogel surfaces, while cells exhibited more cytoplasmic spreading and proliferation when entrapped within softer hydrogels. Hence, this material system contains multiparametric factors that can easily be controlled to modulate the chemical, physical and biological properties of the biomatrix for soft tissue scaffolding and cell presentation to reconstruct lost tissue architecture and physical functionality.

In Vivo Evaluation of a Biodegradable EDC/NHS-Cross-Linked Gelatin Peripheral Nerve Guide Conduit Material

Peripheral nerve regeneration has been evaluated using a biodegradable nerve conduit, which is made of a 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/N-hydroxysuccinimide (NHS) cross-linked gelatin. The EDC/NHS crosslinked gelatin (ENG) conduit is brownish in appearance, and is concentric and round with a smooth outer surface and inner lumen. After subcutaneous implantation on the dorsal side of a rat, the degraded ENG conduit only evoked a mild tissue response, with the formation of a thin tissue capsule surrounding the conduit. Biodegradability of the ENG conduit and its effectiveness as a guidance channel has been examined by its use to repair a 10 mm gap in the rat sciatic nerve. As a result, the tubes degraded throughout the implantation period, but still remained circular with a thin round lumen until they were completely integrated with the enclosed nerves. Successful regeneration through the gap occurred in all the conduits over the three experimental periods of 4, 8, and 12 weeks. Histological observation showed that numerous myelinated axons had crossed through the gap region even at the shortest implantation period of 4 weeks. Peak amplitude, area under the muscle action potential curve, and nerve conductive velocity all showed an increase as a function of the recovery period, which indicates that the nerve had undergone adequate regeneration. These results indicate the superiority of the ENG materials and suggest that the novel ENG conduits provide a promising tool for neuro-regeneration.

3D Bioprinting of Carbohydrazide-Modified Gelatin into Microparticle-Suspended Oxidized Alginate for the Fabrication of Complex-Shaped Tissue Constructs

Extrusion-based bioprinting of hydrogels in a granular secondary gel enables the fabrication of cell-laden three-dimensional (3D) constructs in an anatomically accurate manner, which is challenging using conventional extrusion-based bioprinting processes. In this study, carbohydrazide-modified gelatin (Gel-CDH) was synthesized and deposited into a new multifunctional support bath consisting of gelatin microparticles suspended in an oxidized alginate (OAlg) solution. During extrusion, Gel-CDH and OAlg were rapidly cross-linked because of the Schiff base formation between aldehyde groups of OAlg and amino groups of Gel-CDH, which has not been demonstrated in the domain of 3D bioprinting before. Rheological results indicated that hydrogels with lower OAlg to Gel-CDH ratios possessed superior mechanical rigidity. Different 3D geometrically intricate constructs were successfully created upon the determination of optimal bioprinting parameters. Human mesenchymal stem cells and human umbilical vein endothelial cells were also bioprinted at physiologically relevant cell densities. The presented study has offered a novel strategy for bioprinting of natural polymer-based hydrogels into 3D complex-shaped biomimetic constructs, which eliminated the need for cytotoxic supplements as external cross-linkers or additional cross-linking processes, therefore expanding the availability of bioinks.

Synthesis and Physical Characterization of Poly(ethylene glycol)-Gelatin Conjugates

Poly(ethylene glycol) (PEG) with the terminal group of active ester was coupled to the amino group of gelatin to prepare PEG-grafted gelatin (PEG-gelatin). The affinity chromatographic study revealed that the PEG-gelatin with high degrees of PEGylation did not adsorb onto the gelatin affinity column, in remarked contrast to gelatin alone and the PEG-gelatin with low PEGylation degrees. The former PEG-gelatin showed a critical micelle concentration while it had the apparent molecular size of about 100 nm and a surface charge of almost zero. These findings indicate that the PEG-gelatin formed a micelle structure of which the surface is covered with PEG molecules grafted. When the body distribution of 125I-labeled gelatin and PEG-gelatin after intravenous injection was evaluated, the radioactivity of micellar PEG-gelatin was retained in the blood circulation compared with that of gelatin and the PEG-gelatin of no micelle formation. At the same PEGylation degree, the blood concentration was significantly higher for the PEG-gelatin prepared from PEG with a molecular weight of 12 000 than that of molecular weights of 2000 and 5000. It is concluded that the PEG-gelatin is a drug carrier with a micelle structure which retains in the blood circulation.

Nanogels Derived from Fish Gelatin: Application to Drug Delivery System

The gelatin extracted from mammals of porcine and bovine has been prominently used in pharmaceutical, medical, and cosmetic products. However, there have been some concerns for their usage due to religious, social and cultural objections, and animal-to-human infectious disease. Recently, gelatin from marine by-products has received growing attention as an alternative to mammalian gelatin. In this study, we demonstrate the formation of nanogels (NGs) using fish gelatin methacryloyl (GelMA) and their application possibility to the drug delivery system. The fabrication of fish GelMA NGs is carried out by crosslinking through the photopolymerization of the methacryloyl substituent present in the nanoemulsion droplets, followed by purification and redispersion. There were different characteristics depending on the aqueous phase in the emulsion and the type of solvent used in redispersion. The PBS-NGs/D.W., which was prepared using PBS for the aqueous phase and D.W. for the final dispersion solution, had a desirable particle size (<200 nm), low PdI (0.16), and high drug loading efficiency (77%). Spherical NGs particles were observed without aggregation in TEM images. In vitro release tests of doxorubicin (DOX)-GelMA NGs showed the pH-dependent release behavior of DOX. Also, the MTT experiments demonstrated that DOX-GelMA NGs effectively inhibited cell growth, while only GelMA NGs exhibit higher percentages of cell viability. Therefore, the results suggest that fish GelMA NGs have a potential for nano-carrier as fine individual particles without the aggregation and cytotoxicity to deliver small-molecule drugs.

Macroporous interpenetrating cryogel network of poly(acrylonitrile) and gelatin for biomedical applications

Cryogels are supermacroporous gel network formed by cryogelation of appropriate monomers or polymeric precursors at subzero temperature. The beneficial feature of this system is a unique combination of high porosity with adequate mechanical strength and osmotic stability, due to which they are being envisaged as potential scaffold material for various biomedical applications. One of the important aspect of cryogel is simple approach by which they can be synthesized and use of aqueous solvent for their synthesis which make them suitable for different biological applications. Various modifications of the cryogels have been sought which involves coupling of various ligands to its surfaces, grafting of polymer chain to cryogel surface or interpenetrating networks of two or more polymers to form a cryogel which provides diversity of its applications. In the following work we have synthesized full interpenetrating network of polyacrylonitrile (PAN)-gelatin with varied gelatin concentration. The PAN-gelatin cryogel interpenetrating network is macroporous in nature and has high percentage swelling equilibrium in the range of 862-1,200 with a flow rate greater than 10 ml/min, which characterizes the interconnectivity of pores and convective flow within the network. PAN-gelatin interpenetrating cryogel network has good mechanical stability as determined by Young's modulus which varies from 123 kPa to 819 kPa depending upon the polymer concentration. Moreover they are shown to be biocompatible and support cell growth within the scaffolds.

Synthesis and physicochemical analysis of interpenetrating networks containing modified gelatin and poly(ethylene glycol) diacrylate

The interrelated effects of gelatin modification, content, and poly(ethylene glycol) molecular weight on the melting temperature, surface hydrophilicity, tensile properties, swelling/degradation, and drug-release kinetics of a novel interpenetrating network (IPN) system containing gelatin and poly(ethylene glycol) diacrylate were evaluated. Gelatin content had a large effect on the IPN melting temperature and Delta H. Modifying gelatin with ethylenediaminetetraacetic acid and/or monomethoxy poly(ethylene glycol) monoacetate ester as well as increasing poly(ethylene glycol) diacrylate molecular weight increased the surface hydrophilicity. Increasing the gelatin weight percent increased the IPN elasticity at room temperature. When buffer and elevated temperature were present in the testing environment, the elasticity of all IPNs tested decreased. IPNs showed an enhanced elasticity and strength when compared with glutaraldehyde-fixed gelatin hydrogels. The extent of IPN swelling and degradation was increased by increasing the gelatin content or by modifying gelatin. The time to complete sample degradation was longer for IPNs when compared with gelatin crosslinked with glutaraldehyde. Modifications to the IPN system increased the maximum percent of chlorhexidine digluconate released from the IPNs. The rate of complete drug release was slower from IPNs than from glutaraldehyde-fixed gelatin matrices. A wide range of IPN physicochemical properties was obtained through formulation changes and chemical modifications.

Controllable synthesis, characterization and optical properties of colloidal PbS/gelatin core-shell nanocrystals

Native quantum dots (QDs) made up of semiconductor nanocrystals (NCs) are toxic in nature but due to their excellent optical properties, they have proven themselves to be an attractive choice in biological labeling and targeting. In order to improve the general biocompatibility of lead sulfide (PbS) NCs, we present a new and simple procedure for preparing PbS/gelatin core-shell nanoparticles cross-linked with glutaraldehyde (GA) molecules. The phase composition, morphology, luminescence and in vitro photostability of the samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission electron microscope (TEM) and fluorescence spectroscopy, respectively. The XRD analysis showed that the PbS NCs were of the cubic structure, the mean crystallite size was calculated to be 13.5 nm and the calculated lattice constant using Bragg's equation was 0.5950 nm, which was very close to its value in the standard card (JCPDS No. 5-592). In vitro test revealed that compared with bare PbS NCs, the photostability of the core-shell nanostructure remarkably improved. In addition, possible formation mechanisms of the PbS/gelatin nanoparticles were discussed in detail. Consequently, the advantages of high stability as well as high fluorescent intensity and biocompatibility make the core-shell nanoparticles promising candidates for in vivo biological targeting applications.

Crosslinking of gelatin-based drug carriers by genipin induces changes in drug kinetic profiles in vitro

Hydrogels are extensively studied as carrier matrices for the controlled release of bioactive molecules. The aim of this study was to design gelatin-based hydrogels crosslinked with genipin and study the impact of crosslinking temperature (5, 15 or 25°C) on gel strength, microstructure, cytocompatibility, swelling and drug release. Gels crosslinked at 25°C exhibited the highest Flory-Rehner crosslink density, lowest swelling ratio and the slowest release of indomethacin (Idn, model anti-inflammatory drug). Diffusional exponents (n) indicated non-Fickian swelling kinetics while drug transport was anomalous. Hydrogel biocompatibility, in vitro cell viability, cell cycle experiments with AH-927 and HaCaT cell lines indicated normal cell proliferation without any effect on cell cycle. Overall, these results substantiated the use of genipin-crosslinked hydrogels as a viable carrier matrix for drug release applications.