Enhanced bonding strength of hydrophobically modified gelatin films on wet blood vessels

Hydrophobically Modified Gelatin Particles for Production of Liquid Marbles

The unique properties and morphology of liquid marbles (LMs) make them potentially useful for various applications. Non-edible hydrophobic organic polymer particles are widely used to prepare LMs. It is necessary to increase the variety of LM particles to extend their use into food and pharmaceuticals. Herein, we focus on hydrophobically modified gelatin (HMG) as a base material for the particles. The surface tension of HMG decreased as the length of alkyl chains incorporated into the gelatin and the degree of substitution (DS) of the alkyl chains increased. HMG with a surface tension of less than 37.5 mN/m (determined using equations based on the Young-Dupré equation and Kaelble-Uy theory) successfully formed LMs of water. The minimum surface tension of a liquid in which it was possible to form LMs using HMG particles was approximately 53 mN/m. We also showed that the liquid-over-solid spreading coefficient SL/S is a potential new factor for predicting if particles can form LMs. The HMG particles and the new system for predicting LM formation could expand the use of LMs in food and pharmaceuticals.

Synthesis and fabrication of gelatin-based elastomeric hydrogels through cosolvent-induced polymer restructuring

Hydrogels have a wide range of applications in tissue engineering, drug delivery, device fabrication for biological studies and stretchable electronics. For biomedical applications, natural polymeric hydrogels have general advantages such as biodegradability and non-toxic by products as well as biocompatibility. However, applications of nature derived hydrogels have been severely limited by their poor mechanical properties. For example, most of the protein derived hydrogels do not exhibit high stretchability like methacrylated gelatin hydrogel has ∼11% failure strain when stretched. Moreover, protein derived elastomeric hydrogels that are fabricated from low molecular weight synthetic peptides require a laborious process of synthesis and purification. Biopolymers like gelatin, produced in bulk for pharma and the food industry can provide an alternative for the development of elastomeric hydrogels. Here, we report the synthesis of ureidopyrimidinone (Upy) functionalized gelatin and its fabrication into soft elastomeric hydrogels through supramolecular interactions that could exhibit high failure strain (318.73 ± 44.35%). The hydrogels were fabricated through a novel method involving co-solvent optimization and structural transformation with 70% water content. It is anticipated that the hydrogel fabrication method involves the formation of hydrophobic cores of ureidopyrimidinone groups inside the hydrogel which introduced elastomeric properties to the resulting hydrogel.

A review: Gelatine as a bioadhesive material for medical and pharmaceutical applications

Bioadhesive polymers offer versatility to medical and pharmaceutical inventions. The incorporation of such materials to conventional dosage forms or medical devices may confer or improve the adhesivity of the bioadhesive systems, subsequently prolonging their residence time at the site of absorption or action and providing sustained release of actives with improved bioavailability and therapeutic outcomes. For decades, much focus has been put on scientific works to replace synthetic polymers with biopolymers with desirable functional properties. Gelatine has been considered one of the most promising biopolymers. Despite its biodegradability, biocompatibility and unique biological properties, gelatine exhibits poor mechanical and adhesive properties, limiting its end-use applications. The chemical modification and blending of gelatine with other biomaterials are strategies proposed to improve its bioadhesivity. Here we discuss the classical approaches involving a variety of polymer blends and composite systems containing gelatine, and gelatine modifications via thiolation, methacrylation, catechol conjugation, amination and other newly devised strategies. We highlight several of the latest studies on these strategies and their relevant findings.

Enhanced skin adhesive property of α-cyclodextrin/nonanyl group-modified poly(vinyl alcohol) inclusion complex film

For skin contact medical devices, realizing a strong contact with skin is essential to precisely detect human biological information and enable human-machine interaction. In this study, we aimed to fabricate and characterize an inclusion complex film (ICF) for skin adhesion using α-cyclodextrin (α-CD) and nonanyl group-modified PVA (C9-PVA) under wet conditions. Based on the water insolubility of C9-PVA and the inclusion ability of α-CD for alkyl groups, α-CD/C9-PVA ICF was prepared. Among the prepared ICFs, α-CD/2.5C9-PVA (w/w = 0.5) ICF showed the highest bonding strength and T-peeling strength to porcine skin. Furthermore, α-CD/2.5C9-PVA (w/w = 0.5) ICF had better water vapor transmission rate than that of commercial tapes. In addition, the ion permeability test revealed that α-CD/2.5C9-PVA (w/w = 0.5) ICF exhibited excellent Na and Cl ion permeability. These results demonstrated that the multi-functional α-CD/2.5C9-PVA (w/w = 0.5) ICF can be a promising adhesive for skin contact medical devices.

Bonding a titanium plate and soft tissue interface by using an adhesive bone paste composed of α-tricalcium phosphate and α-cyclodextrin/nonanyl group-modified poly(vinyl alcohol) inclusion complex

Adhesive bone pastes for dental implants and soft tissue interfaces were developed using α-tricalcium phosphate (α-TCP) and α-cyclodextrin (α-CD)/nonanyl group-modified poly(vinyl alcohol) (C9-PVA) inclusion complex solution (ICS). The thixotropic solution of α-CD/C9-PVA ICS was prepared by mixing α-CD and C9-PVA in deionized water. The α-CD/C9-PVA bone paste led to the highest bonding and shear adhesion between commercial pure titanium plates and soft tissue like collagen casing. Moreover, the compressive strength of these pastes reached 14.1 ± 3.8 MPa within 24 h incubation. Young's modulus of the α-CD/C9-PVA bone paste was lower than that of commercial calcium phosphate paste. Furthermore, the surface of α-CD/C9-PVA bone paste demonstrated excellent cell adhesion for cultured L929 fibroblast cells. Overall, the α-CD/C9-PVA bone paste can likely be effectively used to adhere dental implant abutments and soft tissue interfaces.

Enhanced skin adhesive property of electrospun α-cyclodextrin/nonanyl group-modified poly(vinyl alcohol) inclusion complex fiber sheet

Many medical tapes on the market lack sufficient adhesive strength and breathability. Owing to its high biocompatibility, poly(vinyl alcohol) (PVA), a synthetic polymer, has attracted attention in the medical field. In this study, we aimed to prepare an inclusion complex fiber (ICFiber) using α-cyclodextrin (α-CD) and nonanyl-group-modified PVA (C9-PVA) for skin adhesion with improved performance. By changing the concentration of α-CD, six microfiber sheets were fabricated by electrospinning the α-CD/2.3C9-PVA inclusion complex solutions. The bonding strength and energy of the ICFiber sheets on the porcine skin were evaluated. Among the tested ICFiber sheets, the ICFiber-3 (molar ratio of α-CD/C9 groups was 0.612) sheet showed high tensile strength and break strain. The bonding strength and energy of ICFiber-3 sheet on porcine skin were 1.10 ± 0.11 N and 5.07 ± 0.94 J m-2, respectively, in the presence of water. In addition, ICFiber-3 sheet showed a better water vapor transmission rate (0.95 ± 0.02 mL per day) than commercial tapes. These results demonstrate that the α-CD/2.3C9-PVA ICFiber sheet is a promising adhesive for wearable medical devices.

Enhanced Skin Adhesive Property of Hydrophobically Modified Poly(vinyl alcohol) Films

Hydrophobically modified poly(vinyl alcohol) (hm-PVA) films with various alkyl chain lengths were prepared. Their surface/mechanical properties, cytocompatibility, and porcine skin adhesion strength were evaluated. hm-PVAs had 10 °C higher glass transition temperature than poly(vinyl alcohol) (PVA) (33.4 ± 2.5 °C). The water contact angle of the hm-PVA films increased with alkyl chain length and/or hydrophobic group modification ratio. The tensile strength of the hm-PVA films decreased with increasing alkyl chain length and/or hydrophobic group modification ratio. hm-PVA with short chain lengths (4 mol % propanal-modified PVA; 4C3-PVA) had low cytotoxicity compared with long alkyl chain length hm-PVAs (4 mol % hexanal and nonanal-modified PVA; 4C6-PVA and 4C9-PVA). The 4C3-PVA film had the highest porcine skin adhesion strength. Thus, the 4C3-PVA film is promising as an adhesive for wearable medical devices.

Mechanically robust photodegradable gelatin hydrogels for 3D cell culture and in situ mechanical modification

Highly conjugated, hydrophobically modified gelatin hydrogels were synthesized, polymerized and degraded with orthogonal wavelengths of light.

Experimental and computational analysis of a novel flow channel to assess the adhesion strength of sessile marine organisms

Bioadhesives produced by marine macroalgae represent a potential source of inspiration for the development of water-resistant adhesives. Assessing their adhesion strength, however, remains difficult owing to low volumes of adhesive material produced, low solubility and rapid curing time. These difficulties can be circumvented by testing the adhesion strength of macroalgae propagules attached to a substrate. In this paper, we present a simple, novel flow channel used to test the adhesion strength of the germlings of the fucalean alga Hormosira banksii to four substrates of biomedical relevance (PMMA, agar, gelatin and gelatin + lipid). The adhesion strength of H. banksii germlings was found to increase in a time-dependent manner, with minimal adhesion success after a settlement period of 6 h and maximum adhesion strength achieved 24 h after initial settlement. Adhesion success increased most dramatically between 6 and 12 h settlement time, while no additional increase in adhesion strength was recorded for settlement times over 24 h. No significant difference in adhesion strength to the various substrates was observed. Computational fluid dynamics (CFD) was used to estimate the influence of fluid velocity and germling density on drag force acting on the settled organisms. CFD modelling showed that, on average, the drag force decreased with increasing germling number, suggesting that germlings would benefit from gregarious settlement behaviour. Collectively, our results contribute to a better understanding of the mechanisms allowing benthic marine organisms to thrive in hydrodynamically stressful environments and provide useful insights for further investigations.

Surface modification and endothelialization of biomaterials as potential scaffolds for vascular tissue engineering applications

This review highlights the recent developments of surface modification and endothelialization of biomaterials in vascular tissue engineering applications.

Bonding behavior of hydrophobically modified gelatin films on the intestinal surface

The bonding behavior was determined for hydrophobically modified alkaline-treated gelatin on wet porcine intestinal surfaces. The modified gelatin films were obtained by reacting the amino groups of alkaline-treated gelatin with fatty acid chlorides of different alkyl chain lengths, namely, hexanoyl (Hx: C6) chloride, decanoyl (Dec: C10) chloride, and stearoyl (Ste: C18) chloride. Three kinds of the films were prepared, 32HxAlGltn, 24DecAlGltn, and 26SteAlGltn that had substitution ratios of hydrophobic groups to the amino groups of 32HxAlGltn, 24DecAlGltn, and 26SteAlGltn of 32%, 24%, and 26%, respectively. The 32HxAlGltn film had the strongest bonding to porcine intestinal surfaces. A thick 32HxAlGltn film remained on the intestinal surface even after the bonded film was scraped off for the measurement of bonding strength. In addition, the burst strength increased with an increase in the substitution ratio of the Hx group. Thus, the HxAlGltn film with the higher Hx modification ratio has a potential as a sealant material to prevent agglutination of intestinal surfaces.