Rod-shaped gels

During the course of experiments to reveal an electric field effect on the behavior on the photogenerated mobile ions, we found a peculiar phenomenon, reversible bending motion of the rod-shaped gels. The result will also be briefly described. 

Figure 4 shows the size and shape changes of the gel before and after photoirradiation. When the whole gel was irradiated with ultraviolet light, both the gel length and diameter expanded by as much as two times(Figure 4B). When the irradiation beam was localized to one side of the rod shaped gel, the gel showed bending motion (Figure 4D).

Figure 4. Photostimulated size and shape changes of polyacrylamide gels having triphenylmethane leucocyanide groups (3.1 mole %) (A) before photoirradiation, (B) the whole gel being irradiated with ultraviolet light, (C)before photoirradiation, (D) upper side of the rod shaped gel being irradiated.

Reversible Bending of Rod-Shaped Gels in an Electric Field - Macro... 

X 19 X 15 mm) with two parallel platinum electrodes(26). The rod-shaped gel was placed parallel to the electrodes to avoid the contact of the gels with the electrodes. The acrylamide gels containing triphenylmethane leucocyanide groups(25 mm in length and 2 mm in section diameter) were prepared in capillary tubes by the same method as described in the previous section. 

In order to determine quantitatively the response time of the motion, one end of the rod-shaped gel was fixed to the wall and the moving distance of the other free end, 1, from the initial position was measured as a function of irradiation time. Figure 7 shows the photostimulated bending motion of the gel(26 mm in length and 2 mm in section diameter) in an electric fielddO V/cm). The free end moved toward the positive electrode with a initial speed of 0.40 mm/ sec. By changing the polarity of the electric field, the end moved to another direction. Upon switching off the electric field, the bent gel returned to the initial position with a speed of 0.075 mm/ sec,... 

On the contrary to rod shaped gels, slab gels can be dried on a paper sheet after staining and destaining and stored in this rather conventional form. Commercial instruments for slab gel electrophoresis and the destaining accessories can be obtained from e.g., Pharmacia Fine Chemicals, Uppsala, Sweden Desaga, Heidelberg, FRG or Bio-Rad Laboratories, Richmond, CA, USA. 

A collagen-based therapeutic implantable gel technology has recently been developed, in which the dmg moiety (a chemotherapeutic agent) is incorporated within the meshwork of rod-shaped collagen molecules. The collagen matrix is then converted to an injectable gel by a chemical modifier. Changes in the composition and structure of the gel can adjust its solubility, strength and resorption properties. 

The polyacrylamide gel described abobe is the first example showing a reversible deformation of more than 100%. The effect is purely photochemical and reversible. However, this gel has a serious disadvatage in that the response time is slow. To improve this point the effect of electric field on the gel deformation was examined [44]. A rod-shaped polyacrylamide gel containing triphenylmethane leucocyanide groups (25 mm in length and 2 mm in section diameter) was prepared in a capillary tube. The gel rod was inserted between two parallel platinum electrodes in a small... 

Fig. 20. Photostimulated vibrational motion of a rod shaped polyacrylamide gel having 3.1 mol% triphenylmethane leucocyanide groups under an alternating electric field ( + 0.8 v/cm, 0.5 Hz) in water in the preseiK of4x lO MNaCl...

An erodible insert developed as a potential ocular drug delivery system is marketed as a prescription drug for the lubricant properties of the polymer base. Lacrisert is a sterile ophthalmic insert that is used in the treatment of moderate-to-severe dry eye syndrome and is usually recommended for patients unable to obtain symptomatic relief with artificial tear solutions. The insert is composed of 5 mg of hydroxypropylceUulose in a rod-shaped form, about 1.27 mm in diameter and about 3.5 mm long. No preservative is used, since it is essentially anhydrous. The quite rigid cellulose rod is placed in the lower conjunctival sac and first imbibes water from the tears, and after several hours, forms a gel-like mass, which gradually erodes as the polymer dissolves. This action thickens the tear film and provides increased lubrication, which can provide symptomatic relief for dry eye states. It is usually used once or twice daily. 

Figure 6. Photostimulated bending motion of a rod shaped acrylamide gel (25 mm in length and 2 mm in section diameter) having 3.1 mole% triphenylmethane leucocyanide groups in an electric field (10 V/cm) in water (A) before photoirradiation, (B)under ultraviolet irradiation, (C) under ultraviolet irradiation, polarity of the electric field being opposite to that in (B).

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