Page 307 - IJB-10-2

International Journal of Bioprinting 3D-printed diabetic diet

was subjected to an initial shear rate that slowly ramped 65 mg/kg. The glucose level of the blood sample taken from
from 0.1 to 1 s in 60 s, followed by a high shear rate of 200 the rat tail vein was measured with a blood glucometer in
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s which returned to 0.1 s after 6 s. All experiments were the following 7 days. The fasting blood glucose level for
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performed in triplicates at 25 ± 0.1°C. rats with normal blood glucose was 3.95 ± 1.31 mmol/L,
and their blood glucose 120 min after a meal was 5.65 ±
2.4. Texture profile analysis 1.63 mmol/L. Rats with the blood glucose level above
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Texture analysis was performed using the Texture Analyzer 16.7 mmol/L for at least 3 consecutive days were used in
Universal TA (Shanghai Tengba Instrument Technology subsequent gavage experiments. Based on the content
Co., Ltd., China) to obtain force–time curves through for gavage, the rats were divided into three groups—rice
double-cycle compression tests. To ensure the stability, a group, vegetable group, and 3D-print food powder group.
1-cm specimen printed with the FoodBot-D1 was placed Two parallel experiments were designed, in which either
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at the center of the platform. The test parameters were the total mass or the total amount of carbohydrates of the
standardized with a block probe having a trigger load of 5 g, food was controlled. In the equal-mass experiments, 1 g
pre-test speed of 2.0 mm/s, and compressive strain of 45%. of water was added to every 100 mg of food powder, and
The test and post-test speeds were also set to 2.0 mm/s. the mixture was fully homogenized. Each animal received
The measured textural properties included the hardness, 1 mL of the homogenized food powder. In the equal-
chewiness, adhesiveness, gumminess, springiness, and carbohydrate experiments, the total carbohydrate content
stringiness. Each test was repeated three times for each of each food for gavage was set to 2 g/kg of body weight.
specimen, and the results were averaged and normalized The glucose levels at 0 min (the time of oral gavage), 30
to the highest value obtained in the group. 35 min, 60 min, 90 min, and 120 min were measured by using
2.5. Scanning electron microscopy a handheld electrochemical glucose meter and test strip.
The microstructure of the food inks was analyzed using Both the peak glucose level and the area under the curve
scanning electron microscopy (SEM; JSM-7600F, JEOL (AUC) for glucose were compared for both the equal-mass
Ltd., Tokyo, Japan). A small amount of food inks was and equal-carbohydrate scenarios.
spread onto a Petri dish, frozen at -20°C for 6 h, and then 2.8. Fourier-transform infrared spectroscopy
subjected to vacuum freeze-drying for 72 h. The dried The measurement of infrared spectra of food ink
samples were mounted on circular stubs with double-sided formulations using the Spectrum Two (L1600300) Fourier-
adhesive tapes, sputter-coated with gold (7 Pa and 8 W for transform infrared (FT-IR) spectrometer was performed
40 s), and imaged at magnifications of 500× and 1500× in accordance with the method described by Liu et al. For
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with an excitation voltage of 15 kV. sample preparation, each food ink formulation was freeze-
2.6. International Dysphagia Diet Standardization dried and ground into powder using a mortar. Subsequently,
Initiative tests the samples were thoroughly mixed with potassium
International Dysphagia Diet Standardization Initiative bromide (KBr) at a 1:100 ratio. The measurements were
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(IDDSI) fork pressure test was adopted to qualitatively carried out with the wavenumber range of 4000 cm to 400
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assess the texture of the 3D-printed food and gauge their cm , at an ambient temperature of 25°C. The scan speed
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suitability for patients with oral ulcer. The framework was set at 0.2 cm/s, and the resolution was set to 4 cm .
categorizes texturally modified food into eight levels (0 to 2.9. Statistical analysis
7) and proposes a combination of tests to determine the The data obtained were analyzed using GraphPad Prism
appropriate level of each food. Food inks for 3D printing software, and the results were expressed as means ± standard
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usually belong to Level 4 (pureed; extremely thick) or Level error of the mean. Statistical significance was evaluated
5 (minced and moist), which are suitable for fork pressure using analysis of variance (ANOVA). Significance levels
test. For the fork pressure test, the 3D-printed specimens were indicated above specific columns, where * denotes
were pressed with a fork by thumb until blanching p ≤ 0.05, ** denotes p ≤ 0.01, *** denotes p ≤ 0.001, and
(approximate pressure of 17 kPa), which is equivalent to **** denotes p ≤ 0.0001. Radar charts for textural profile
the tongue pressure used during swallowing. analysis were generated using Microsoft Excel.

2.7. Animal experiments
One week before streptozotocin (STZ) injection, male 3. Results and discussion
Sprague-Dawley rats (200–250 g) were purchased from 3.1. Printability and rheological properties of
Dashuo Co. Ltd. (Chengdu, China) and fed to fully adapt to food inks
the environment. The 1% STZ solution dissolved in citrate The printability of the food inks was assessed through visual
buffer was injected intraperitoneally into rats at a dose of inspection of the hexagons 3D-printed with respective

Volume 10 Issue 2 (2024) 299 doi: 10.36922/ijb.1862