Incorporation of dumbbell-shaped and Y-shaped cross-linkers in adjustable pullulan/polydopamine hydrogels for selective adsorption of cationic dyes.

Hydrogel adsorbents have attracted considerable attention due to their sludge minimization, good water permeability and renewable performance. Here, a promising strategy for the one-step preparation of pullulan/polydopamine hybird hydrogels (PPGels) was presented. Dumbbell-shaped cross-linker neopentyl glycol diglycidyl ether (NGDE, 2 arms) and Y-shaped cross-linker trimethylolpropane triglycidyl ether (TTE, 3 arms) were selected to study the relationship between cross-linker structure and hydrogel performances. The NGDE possessing less molecular repulsive force and higher reactivity demonstrated more effective cross-linking with the pullulan, which leaded to a decrease in pore size of the hydrogel. Meanwhile, the introduction of polydopamine significantly enhanced the adsorption ability and gave the resulting hybrid gel the specific selectivity toward cationic dyes (96 mg/g for crystal violet, 25.8 mg/g for methylene blue and barely not adsorption for azophloxine). Our data suggested that the electrostatic interaction played a vital role in the dye adsorption process, and the adsorption data could be explained by pseudo-second-order model and Langmuir isotherm model. Furthermore, the obtained PPGel could be easily separated after adsorption. This study describes the relationship between cross-linker structure and properties of pullulan/polydopamine hybrid gels, which provides a new strategy to create polysaccharide-based adsorbents for wastewater remediation.

Applicability of the Tanaka-Johnston and Moyers mixed dentition analyses in Northeast Han Chinese.

OBJECTIVES: To assess applicability of the Tanaka-Johnston and Moyers prediction methods in a Han ethnic group from Northeast China and to develop prediction equations for this same population. DESIGN: Cross-sectional study. SETTING: Department of Orthodontics, School of Stomatology, Jiamusi University, Heilongjiang, China. PARTICIPANTS: A total of 130 subjects (65 male and 65 female) aged 16-21 years from a Han ethnic group of Northeast China were recruited from dental students and patients seeking orthodontic treatment. Ethnicity was verified by questionnaire. MATERIAL AND METHODS: Mesio-distal tooth width was measured using Digital Vernier calipers. Predicted values were obtained from the Tanaka-Johnston and Moyers methods in both arches were compared with the actual measured widths. Based on regression analysis, prediction equations were developed. RESULTS: Tanaka-Johnston equations were not precise, except for the upper arch in males. However, the Moyers 85th percentile in the upper arch and 75th percentile in the lower arch predicted the sum precisely in males. For females, the Moyers 75th percentile predicted the sum precisely for the upper arch, but none of the Moyers percentiles predicted in the lower arch. CONCLUSIONS: Both the Tanaka-Johnston and Moyers method may not be applied universally without question. Hence, it may be safer to develop regression equations for specific populations. Validating studies must be conducted to confirm the precision of these newly developed regression equations.

Facile fabrication of functional hydrogels consisting of pullulan and polydopamine fibers for drug delivery.

With the rapid development of biomedicine applications, more flexible and efficient fabrication strategies are required for drug delivery vehicles. Naturally resourced polymers have gained considerable attention for construction of drug carriers. Here, biocompatible hydrogel reservoir system (named PHG-PDA) based on pullulan and polydopamine (PDA) are designed and fabricated by one-pot incorporation of PDA fibers into pullulan hydrogel (PHG). The structure and performance of the PHG-PDAs can be nicely adjusted by regulating the content of PDA fibers in precursor hydrogel solutions. Crystal violet is used as a drug prototype and introduced into hydrogels via swelling-diffusion approach. We found that the drug loading process followed the pseudo-second-order model and Langmuir isotherm model, while the drug releasing process was pH-responsive, and the cumulative release reached 60.3% and 87% at pH 7.4 and 5.0, respectively. In vitro cytotoxicity studies on L929 cells demonstrated that our hydrogels were nontoxic even in a high concentration (3.4 mg/mL). In sum, these biocompatible PHG-PDAs with tunable physicochemical properties are promising systems for drug delivery.