Injectable, pore-forming, self-healing, and adhesive hyaluronan hydrogels for soft tissue engineering applications.

Most existing injectable hydrogels are non-porous, thereby lacking a microporous structure to promote cell ingrowth. Also, most hydrogels do not effectively adhere to the host tissue. The present study describes an injectable double network hydrogel formed by combining two hyaluronic acid (HA) derivatives, namely dopamine grafted HA (DAHA) and methacrylated HA (HAMA). These constituents instantly form a physically crosslinked network through Fe3+-dopamine coordination, and confer fast gelation, pore formation, and self-healing properties to the hydrogel. Photocroslinked upon UV exposure, HAMA forms a chemically crosslinked network, thereby improving mechanical and degradation properties. The adhesive properties of this hydrogel are attributed to the presence of dopamine groups, inspired by mussel creatures. Proper modification of HA chains was confirmed by NMR spectroscopy. The physical, mechanical, rheological, and biological properties of the new hydrogels were quantified in wet laboratory conditions. The results revealed that the DAHA/HAMA hydrogel rapidly forms a self-healing microporous adhesive scaffold with a 26.9 µm pore size, 29.4 kPa compressive modulus, and 12.8 kPa adhesion strength in under 6 s. These findings suggest that the new hydrogel is a promising candidate for in situ repair of soft tissues, particularly mechanically dynamic ones such as the vocal folds, cartilage, and dermis.

Reliability and validity of a quick test of cognitive speed (AQT) in screening for mild cognitive impairment and dementia.

BACKGROUND: Cognitive disorders are one of the important issues in old age. There are many cognitive tests, but some variables affect their results (e.g., age and education). This study aimed to evaluate the reliability and validity of A Quick Test of Cognitive Speed (AQT) in screening for mild cognitive impairment (MCI) and dementia. METHODS: This is a psychometric properties study. 115 older adults participated in the study and were divided into three groups (46 with MCI, 24 with dementia, and 45 control) based on the diagnosis of two geriatric psychiatrists. Participants were assessed by AQT and Mini-Mental State Examination (MMSE). Data were analyzed using Pearson correlation, independent t-test, and ROC curve by SPSS v.23. RESULTS: There was no significant correlation between AQT subscales and age and no significant difference between the AQT subscales in sex, educational levels. The test-retest correlations ranges were 0.84 from 097. Concurrent validity was significant between MMSE and AQT. Its correlation was with Color - 0.78, Form - 0.71, and Color-Form - 0.72. The cut-off point for Color was 43.50 s, Form 52 s, and Color-Form 89 s were based on sensitivity and specificity for differentiating older patients with MCI with controls. The cut-off point for Color was 62.50 s, for Form 111 s, and Color-Form 197.50 s based on sensitivity and specificity measures for differentiating older patients with dementia and MCI. CONCLUSION: The findings showed that AQT is a suitable tool for screening cognitive function in older adults.

Electroactive and antioxidant injectable in-situ forming hydrogels with tunable properties by polyethylenimine and polyaniline for nerve tissue engineering.

The injectable in-situ forming electroconductive hydrogels with antioxidant activity are promising candidates for nerve tissue engineering. In this study, we synthesized and developed a gelatin-graft-polyaniline/periodate-oxidized alginate hydrogel through the introduction of branched polyethylenimine (PEI) to improve the rheological properties. Moreover, antioxidant property, electroconductivity and the effect of external electrical stimulus on the nerve cell behavior were investigated. The results showed that by increasing the polyaniline content, the antioxidant activity, pore sizes, and swelling ratio of the hydrogel were increased, while the crosslinking density and storage modulus were decreased. The introduction of PEI accelerated the gelation time, decreased swelling ratio and pore size, and increased the storage modulus and crosslinking density. Cell studies showed that all formulations had supported the viability of P19 embryonic carcinoma cells with the neuritis elongation in the presence of the external electrical-stimulus. Gene expression of the neuronal markers, including Nestin, Pax-6, and ß-tubulin III, was increased in all hydrogels; In addition, electrical stimulation significantly elevated the expression of these markers in high polyaniline-content hydrogel compared to the polyaniline-free hydrogel. In conclusion, the results suggest that the prepared injectable electroconductive hydrogels can be a promising approach for neural tissue engineering.

Development of an oxygen-releasing electroconductive in-situ crosslinkable hydrogel based on oxidized pectin and grafted gelatin for tissue engineering applications.

Injectable hydrogels with conductivity are highly desirable as scaffolds for the engineering of various electrical stimuli-responsive tissues, including nerve, muscle, retina, and bone. However, oxygen deprivation within scaffolds can lead to failure by causing cell necrosis. Therefore, an oxygen release conductive injectable hydrogel can serve as a promising support for the regeneration of such tissues. In the present study, H2O2-loaded polylactic acid microparticles were fabricated. Then, gelatin-graft-polypyrrole with various pyrrole contents and periodate-oxidized pectin were synthesized, and consequently, injectable conductive hydrogel/microparticle scaffolds, inside which catalase was grafted and trapped, were obtained. The results revealed that spherical particles with a mean diameter of 60.39 µm and encapsulation efficiency of 49.64 %, which persistently provided oxygen up to 14 days, were achieved. Investigations on hydrogels revealed that with the increase of pyrrole content of gelatin-graft-polypyrrole from 0 to 15 %, the swelling ratio, pore size, porosity, and conductivity were increased from 6.5 to 11.8, 173.13 µm-295.96 µm, 79.7%-93.8%, and from 0.06 mS/m to 2.14 mS/m, respectively. On the other hand, the crosslinking degree and compressive modulus of hydrogels were shown to decrease from 67.24%-27.35%, and from 214.1 kPa to 64.4 kPa, respectively. Moreover, all formulations supported cell viability and attachment. Overall, the hydrogel/particle scaffold with the merits of electrical conductivity, injectability, compatibility, and sustained oxygen release can be used as a tissue engineering scaffold, promoting the regeneration of electricity responsive tissues. Considering all the aforementioned characteristics and behavior of the fabricated scaffolds, they may be promising candidates for bone tissue engineering applications.