Filmogenic Cs solutions were prepared by mixing acetic acid (AC) with Cs for 1 h at room temperature. These solutions were labeled according to the amount of Cs used (wt%), follows by the molarity of each AC solution (Table 1). Each one of these solutions were poured into plastic petri dishes (10 mL), and placed in an oven and dried for 30 h at 50 °C (0.60 atm) until a constant weight was obtained.

Table 1

Label	Cs (wt%)	Acetic acid Solution		Cs/AC Solution pH
		Molarity	pH
1.17 Cs	1	0.17	3.05	4.59
1.30 Cs	1	0.30	2.89	4.63
3.17 Cs	3	0.17	3.05	4.9
3.30 Cs	3	0.30	2.89	4.69
7.17 Cs	7	0.17	3.05	6.51
7.30 Cs	7	0.30	2.89	5.58

CanBn and CorBn specimens were obtained from the hip of a healthy cow (3 years of age, 275 kg). These specimens were subjected to a mechanical treatment to remove the organic tissue. Then, the bare bones were cut into small pieces (1.0 × 0.5 × 0.30 cm³), which were coated using programmed equipment, with dip-coating speed of 20 mm/s with a residence time of 5 sec and 4 cycles of repetition. After that, the coating pieces were dried in a vacuum oven at 50 °C (0.60 atm) for 30 h.

Fourier transform infrared (FTIR) spectra were obtained under standard ambient conditions (25 °C, 0.987 atm) in a Bruker Tensor 27 FTIR, with a wave number range of 400 - 4000 cm^-1 by ATR. The deacetylation percent of Cs was calculated using the equation Brugnrott [12].

The surface morphology was analyzed by scanning electron microscopy (SEM) in a JEOL JSM-5300 electron microscope under a resolution of 100 nm. Previous to the SEM analysis, the samples were coated with graphite.

Microhardness measurements were carried out by means of a LEITZ WETZLAR tester (7756 model). The pre treatment consisted in dipping the sample into commercial resin, after curing a mirror-polishing process was applied. The tests were carried out under standard ambient conditions. The microindentation was held for 5sec with an applied load (P) at 0.025 Kgf. On each sample, 7 microindentation tests were performed.

Diffraction patterns of the samples were observed by diffraction X-ray (DRX) using an X-ray diffractometer Bruker D8 Advance with primary Göbel mirror optics and scintillation detector. The wavelength was 1.5406 Å of Cu Κ_ɑ1 with 40 kV and 40 mA. Database Powder Diffraction File (PDF-2) International Center of Diffraction Data (ICDD) was used to identify the present phases.

Figure 1 shows the FTIR spectra of all Cs dry films. Inset A and B show the zoomed view around 3120 and 1600 cm^-1 respectively, which correspond to absorptions of OH and NH groups. In both cases, the highest and lowest intensity corresponded to the 1.17Cs and 3.17Cs films, respectively.

Figure 1

The film 1.17Cs exhibited the largest number of free polar groups and the film 3.17Cs presented the lowest number of these groups (with highest intramolecular interactions).

In order to relate the mechanical behavior with the Cs/bone interaction response the 3.17Cs and 3.30Cs films were selected. Based on FTIR data, the degree of deacetylation of Cs was confirmed about 81.77 %.

According to Figure 2, signals were related to the hydroxyapatite phase. The band at 1022 cm^-1 was assigned to PO₄ ^-3, where the highest intensity was shown for CorBn; so due to collagen, signals at 1550 and 1240 cm^-1 showed the presence of organic phase derived of existence of primary and tertiary amides respectively [13,14].

Figure 2

Figures 3 and 4 show the FTIR results of Cs/CanBn and Cs/CorBn respectively. In both cases, the 1022 cm^-1 signal (assigned to PO₄ ^-3) decreased by the Cs addition, where samples such as 3.30Cs/CanBn and 3.17Cs/CorBn exhibited the lowest intensities.

Figure

Figure 4

Figure 5 shows the SEM analysis of Cs films, where some agglomerations were due to high Cs concentration.

Figure 5

The thickness as function of Cs and AC concentration are presented in Figure 6 and Table 2. The highest and lowest values of Cs were obtained at 7 and 1 wt% of Cs respectively. As consequence of the high AC concentration (0.30 M) the values of thickness decreased. This was because the Cs molecules were arranged closely due to an excess of AC.

Table 2

Cs film	Average thicknesses (µm)	Thckness change (%)*
1.17Cs	7.20	----
3.17Cs	16.0	222.22
7.17Cs	28.0	388.00
1.30Cs	18.0	--
3.30Cs	20.0	111.11
7.30Cs	24.0	133.33

^*

Regarding the first filmogenic solution.

Microindentation hardness testing was performed on Cs/CanBn and Cs/CorBn samples (Table 3). For the CanBn, the sample 3.17Cs/CanBn showed the highest hardness. It was 25.76 % harder than the uncoated bone. After this value, the hardness decreased as effect of an increment in Cs concentration.

Table 3

Coating Bone	Microhardness(GPa)		Percent difference of micro-hardness (%)
	Bone Uncoated	Bone Coated
1.17Cs/CanBn	28.34	29.84	5.29
1.30Cs/CanBn	28.34	34.44	21.521
3.17Cs/CanBn	28.34	35.64	25.76
3.30Cs/CanBn	28.34	22.05	-22.19
7.17Cs/CanBn	28.34	18.3	-35.43
7.30Cs/CanBn	28.34	19.5166	-31.13
3.17Cs/CorBn	35.65	34.67	-2.75
3.30Cs/CorBn	35.65	41.56	16.58

The sample 3.30Cs/CorBn showed the highest hardness, which was 16.58 % harder than the uncoated bone, from 35.65 to 41.56 GPa. This increase in hardness indicates the associations of Cs molecules, as well as the association of Cs molecules with bone. Thus, penetration resistance was the result of a tight arrangement between Cs chains.

XRD patterns of Cs/bone samples are shown in Figure 7. The existence of Cs in the sample was clearly reveled for signal at 20 °. This crystalline signal was more notorious for the 3. 17Cs/CanBn and 7.30Cs/CanBn samples. However, for the sample 1.30Cs/CanBn did not exist a detectable signal, indicating the absence of crystalline phases. The other signals were characteristics of the compact hexagonal crystal structure of hidroxiapatite [15, 16]. Additionally, strong signals of crystallinity are presented in 1.17Cs/CanBn, 3.17Cs/CanBn, 3.30Cs/CanBn, 7.17Cs/CanBn and 7.30Cs/CanBn samples. Thus, the crystallinity was increased as consequence of an increase in the AC concentration. Figure 8 shows the XRD patterns of CorBn 3.17Cs/CorBn and 3.30Cs/CorBn. These results gave evidence of the presence of Cs, indicating that Cs has been embedded into the bone matrix. Moreover, it was observed that crystallinity was increased because of AC concentration. Thus, the 3.30Cs /CorBn exhibited the higher crystallinity.

Figure 7

Figure 8