Tissue-Adhesive Hydrogel Spray System for Live Cell Immobilization on Biological Surfaces

Gelatin hydrogels are used as three-dimensional cell scaffolds and can be prepared using various methods. One widely accepted approach involves crosslinking gelatin amino groups with poly(ethylene glycol) (PEG) modified with N-hydroxysuccinimide ester (PEG-NHS). This method enables the encapsulation of live cells within the hydrogels and also facilitates the adhesion of the hydrogel to biological tissues by crosslinking their surface amino groups. Consequently, these hydrogels are valuable tools for immobilizing cells that secrete beneficial substances in vivo. However, the application of gelatin hydrogels is limited due to the requirement for several minutes to solidify under conditions of neutral pH and polymer concentrations suitable for live cells. This limitation makes it impractical for use with biological tissues, which have complex shapes or inclined surfaces, restricting its application to semi-closed spaces. In this study, we propose a tissue-adhesive hydrogel that can be sprayed and immobilized with live cells on biological tissue surfaces. This hydrogel system combines two components: (1) gelatin/PEG-NHS hydrogels and (2) instantaneously solidifying PEG hydrogels. The sprayed hydrogel solidified within 5 s after dispensing while maintaining the adhesive properties of the PEG-NHS component. The resulting hydrogels exhibited protein permeability, and the viability of encapsulated human mesenchymal stem/stromal cells (hMSCs) remained above 90% for at least 7 days. This developed hydrogel system represents a promising approach for immobilizing live cells on tissue surfaces with complex shapes

Tissue-Adhesive Hydrogel Spray System for Live Cell Immobilization on Biological Surfaces

Gelatin hydrogels are used as three-dimensional cell scaffolds and can be prepared using various methods. One widely accepted approach involves crosslinking gelatin amino groups with poly(ethylene glycol) (PEG) modified with N-hydroxysuccinimide ester (PEG-NHS). This method enables the encapsulation of live cells within the hydrogels and also facilitates the adhesion of the hydrogel to biological tissues by crosslinking their surface amino groups. Consequently, these hydrogels are valuable tools for immobilizing cells that secrete beneficial substances in vivo. However, the application of gelatin hydrogels is limited due to the requirement for several minutes to solidify under conditions of neutral pH and polymer concentrations suitable for live cells. This limitation makes it impractical for use with biological tissues, which have complex shapes or inclined surfaces, restricting its application to semi-closed spaces. In this study, we propose a tissue-adhesive hydrogel that can be sprayed and immobilized with live cells on biological tissue surfaces. This hydrogel system combines two components: (1) gelatin/PEG-NHS hydrogels and (2) instantaneously solidifying PEG hydrogels. The sprayed hydrogel solidified within 5 s after dispensing while maintaining the adhesive properties of the PEG-NHS component. The resulting hydrogels exhibited protein permeability, and the viability of encapsulated human mesenchymal stem/stromal cells (hMSCs) remained above 90% for at least 7 days. This developed hydrogel system represents a promising approach for immobilizing live cells on tissue surfaces with complex shapes

Tissue-Adhesive Hydrogel Spray System for Live Cell Immobilization on Biological Surfaces

Gelatin hydrogels are used as three-dimensional cell scaffolds and can be prepared using various methods. One widely accepted approach involves crosslinking gelatin amino groups with poly(ethylene glycol) (PEG) modified with N-hydroxysuccinimide ester (PEG-NHS). This method enables the encapsulation of live cells within the hydrogels and also facilitates the adhesion of the hydrogel to biological tissues by crosslinking their surface amino groups. Consequently, these hydrogels are valuable tools for immobilizing cells that secrete beneficial substances in vivo. However, the application of gelatin hydrogels is limited due to the requirement for several minutes to solidify under conditions of neutral pH and polymer concentrations suitable for live cells. This limitation makes it impractical for use with biological tissues, which have complex shapes or inclined surfaces, restricting its application to semi-closed spaces. In this study, we propose a tissue-adhesive hydrogel that can be sprayed and immobilized with live cells on biological tissue surfaces. This hydrogel system combines two components: (1) gelatin/PEG-NHS hydrogels and (2) instantaneously solidifying PEG hydrogels. The sprayed hydrogel solidified within 5 s after dispensing while maintaining the adhesive properties of the PEG-NHS component. The resulting hydrogels exhibited protein permeability, and the viability of encapsulated human mesenchymal stem/stromal cells (hMSCs) remained above 90% for at least 7 days. This developed hydrogel system represents a promising approach for immobilizing live cells on tissue surfaces with complex shapes

Migration Behavior of Rodlike dsDNA under Electric Field in Homogeneous Polymer Networks

We investigated the migration behavior of rodlike dsDNA in polymer gels and polymer solutions. Tetra-PEG gel, which has a homogeneous network structure, was utilized as a model system, allowing us to systematically tune the polymer volume fraction and molecular weight of network strand. Although we examined the applicability of the existing models, all the models failed to predict the migration behavior. Thus, we proposed a new model based on the Ogston model, which well explained the experimental data of polymer solutions and gels. The polymer volume fraction determined the maximum mobility, while the network strand governed the size sieving effect. From these results, we conclude that the polymer network with lower polymer volume fraction and smaller network strand is better in terms of size separation. The homogeneous polymer network is vital for understanding of particles’ dynamics in polymer network and a promising material for high-performance size separation

Degradation Behavior of Polymer Gels Caused by Nonspecific Cleavages of Network Strands

We report a systematical study of degradation behavior of hydrogels that suffer from the nonspecific cleavage on the network strands. The volume of the gel specimens increased with the degradation progress, and denoted the temperature dependence and the network strand length dependence. Our new model based on the pseudo-first-order cleavage kinetics of the chemical bonds on the network strands well agreed with the degradation behavior. The estimated apparent degradation rate constants of the network strands were linear function of their length, corresponding to the network strand length dependence on the macroscopic volume change of the gel specimens. The estimated degradation rate constants of the chemical bonds on the network stand, which were ether and amide bond, obeyed the transition state theory. The calculated activation enthalpy of each bond was in the range of the values in previous studies, indicating the validity of our modeling

Electrophoretic Mobility of Double-Stranded DNA in Polymer Solutions and Gels with Tuned Structures

We report a systematic experimental study on the migration behavior of double-stranded DNA (dsDNA) in polymer networks with precisely controlled network structures. The electrophoretic mobility (μ) appeared to be a power law function of the number of base pairs (<i>n</i>), μ ∼ <i>n</i>^–γ, with 0.36 < γ < 1.46. The variance in γ has been commonly explained using the reptation model with constraint release or using the entropic trapping (ET) model. However, our results indicated that the μ values were expressed as products of a power law function and an exponential function of <i>n</i>, which differs from any of the existing models. The power law function terms corresponded to the existing models, the Rouse model or the reptation model. In polymer gels, we observed a crossover from the Rouse to the reptation model with an increase in <i>n</i>, while the migration behavior in polymer solutions always obeyed the Rouse model. These results revealed that the continuous change in γ was accommodated by the exponential function terms

<i>Gli1</i> Haploinsufficiency Leads to Decreased Bone Mass with an Uncoupling of Bone Metabolism in Adult Mice

<div><p>Hedgehog (Hh) signaling plays important roles in various development processes. This signaling is necessary for osteoblast formation during endochondral ossification. In contrast to the established roles of Hh signaling in embryonic bone formation, evidence of its roles in adult bone homeostasis is not complete. Here we report the involvement of <i>Gli1</i>, a transcriptional activator induced by Hh signaling activation, in postnatal bone homeostasis under physiological and pathological conditions. Skeletal analyses of <i>Gli1</i>^+/− adult mice revealed that <i>Gli1</i> haploinsufficiency caused decreased bone mass with reduced bone formation and accelerated bone resorption, suggesting an uncoupling of bone metabolism. Hh-mediated osteoblast differentiation was largely impaired in cultures of <i>Gli1</i>^+/− precursors, and the impairment was rescued by <i>Gli1</i> expression via adenoviral transduction. In addition, <i>Gli1</i>^+/− precursors showed premature differentiation into osteocytes and increased ability to support osteoclastogenesis. When we compared fracture healing between wild-type and <i>Gli1</i>^+/− adult mice, we found that the <i>Gli1</i>^+/− mice exhibited impaired fracture healing with insufficient soft callus formation. These data suggest that <i>Gli1</i>, acting downstream of Hh signaling, contributes to adult bone metabolism, in which this molecule not only promotes osteoblast differentiation but also represses osteoblast maturation toward osteocytes to maintain normal bone homeostasis.</p></div

Radiological findings of long bones in wild-type (WT) and <i>Gli1</i>^+/− mice.

<p>(<b>A</b>) Three-dimensional micro-computed tomography (3D-micro-CT) images of the distal femurs of representative 8-week-old WT and <i>Gli1</i>^+/− male mice. Sagittal sections, transverse sections, and 3D reconstruction images of the primary spongiosa are shown for each genotype. Bar, 1 mm. (<b>B</b>) Histomorphometric analyses of 3D-micro-CT data. BMD, bone mineral density; BV/TV, bone volume per tissue volume; Tb.Th, trabecular thickness; Tb.N trabecular number parameters. Data are means ± SDs of eight male mice per genotype. *p<0.05 vs. WT.</p

Survival rate of <i>Gli1</i> mutant mice during postnatal 10 days.

<p>Percentages are in parentheses.</p><p>Survival rate of <i>Gli1</i> mutant mice during postnatal 10 days.</p

Comparison of bone fracture healing between 8-week-old WT and <i>Gli1</i>^+/− mice.

<p>(<b>A</b>) Soft X-ray pictures of the fracture sites of all WT (n = 8) and <i>Gli1</i>^+/− (n = 8) male mice tested at 2 weeks after the fracture. (<b>B</b>) Representative micro-CT images of the callus in WT and <i>Gli1</i>^+/− male mice. Bar, 1 mm. (<b>C</b>) The areas of horizontal cross-sections at fracture lines (left) and the volume of the calluses (right) of WT and <i>Gli1</i>^+/− mice, calculated using 3D-micro-CT data. Data are means ± SDs of eight mice per genotype. *p<0.05 vs. WT. (<b>D</b>) H&E and alcian blue double staining of the calluses 2 weeks after the fracture. Bar, 200 µm.</p