Objective To develop a wireless sensor module for wound temperature and pressure (hereinafter referred to as wireless sensor module), and to carry out related characteristic test and biosafety evaluation.
Methods (1) The structure and working mode of the wireless sensor module were designed. The temperature and humidity sensor welded at one end of the flexible cable and the pressure sensor were simultaneously connected with the printed circuit board, which was welded with the Bluetooth transmitter, microprocessor, and power interface to establish a wireless sensor module. A mobile data receiving application was developed and the monitoring values of the wireless sensor module exposed to the air were read through the Bluetooth function on the smart phone. (2) The temperature of a 35-42 ℃ hot water bag was measured by the wireless sensor module and an infrared thermometer at the same time, and 30 pairs of data were compared with correlation analysis performed. (3) The vacuum sealing drainage material was pasted on the arm of the second author, and the wireless sensor module was placed in the condition of negative pressure. The negative pressure values measured by the wireless sensor module and the negative pressure meter values were recorded at the same time, and 14 pairs of data were compared with correlation analysis performed. (4) The corresponding material extract was prepared by adding 1 mL normal saline per 3 square centimeters surface area of the pressure sensor or flexible cable with temperature and humidity sensor welded respectively. Twenty 6-8 week-old female C57BL/6 mice were weighed before experiment and divided into pressure sensor extract group, flexible cable extract group, mixed extract group, and normal saline group according to the random number table (
n=5). The abnormal toxic reactions of mice were observed after intraperitoneal injection of pressure sensor extract, flexible cable with temperature and humidity sensor welded extract, 1∶1 mixed extract of pressure sensor extract and flexible cable with temperature and humidity sensor welded extract, and normal saline for 50 mL/kg in corresponding groups. The body mass of mice was weighed at 24, 48, and 72 hours after injection, and the toxicity of the materials was evaluated comprehensively. (5) Four Japanese big ear white rabbits aged 3-6 months were selected, and there was no limit between male and female. Two regions on the left side of the spine were applied with aseptic gauze as aseptic gauze group, and two areas on the right side of the spine were applied with wireless sensor module as wireless sensor module group. The skin status of each region was evaluated at 1, 12, 24, 48 hours after application, and the score according to the skin irritation score standard was recorded. (6) The corresponding material extract was prepared by adding 1 mL serum-free Dulbecco′s modification of Eagle′s medium (DMEM) per 1 square centimeter surface area of the pressure sensor or flexible cable with temperature and humidity sensor welded respectively. L-929 fibroblasts were divided into pressure sensor extract group, flexible cable extract group, phenol control group, and medium control group. The corresponding extract was added in the first two groups, the phenol control group was added with 64 g/L phenol, and the medium control group was cultured with serum-free DMEM. The total volumes of the above four groups were all 100 μL. The absorbance values on the 2nd, 4th, 7th day of culture were detected by methyl thiazolyl tetrazolium method to calculate the cell proliferation rate (
n=6 at each time point) and to grade the cytotoxicity. Data were statistically analyzed with paired samples
t test, Wilcoxon signed rank test, Pearson correlation analysis, Spearman correlation analysis, Mann-Whitney
U test, analysis of variance for repeated measurement, analysis of variance for factorial design, one-way analysis of variance, and Bonferroni correction.
Results (1) The smart phone successfully received the air temperature, humidity, and pressure information detected by the wireless sensor module through the Bluetooth function. (2) The temperature of the hot water bag measured by the wireless sensor module was (37.7±1.7) ℃, which was close to (37.7±1.7) ℃ of the infrared thermometer (
t=-0.112,
P>0.05), and there was a significant positive correlation between them (
r=0.996,
P<0.01). (3) The negative pressure of arm under negative pressure material measured by the wireless sensor module was -36.7 (-38.8, -27.4) kPa, which was significantly lower than -22.7 (-32.7, -12.5) kPa of negative pressure meter (
Z=-3.235,
P<0.01), but there was a significant positive correlation between their absolute values (
ρ=1.000,
P<0.01). (4) There was no abnormal toxic reaction in all groups of rats, and there was no statistically significant difference in body mass among the four groups of mice (
F=3.132,
P>0.05). (5) The scores of skin irritation in application region of rats in the two groups were similar at 1, 12, 24, 48 hours after application (
Z=-1.000, <0.001, -0.620, <0.001,
P>0.05). (6) At each time point of culture, compared with that of medium control group, the cell proliferation rate increased significantly in pressure sensor extract group and flexible cable extract group (
P<0.01) but decreased significantly in phenol control group (
P<0.01). On the 2nd, 4th, 7th day of culture, the cytotoxicity grade of phenol control group was 1, 1, and 2 respectively, and the cytotoxicity grade of each extract group was 0.
Conclusions The wireless sensor module integrates temperature, humidity, and pressure sensors, which can monitor local temperature and pressure and realize the visualization of parameters on the mobile application program. The measurement of temperature is accurate and the pressure measurement results are consistent with the values of the negative pressure meter with good biosafety. It possesses a big value in clinical application and prospects for development.
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