Methotrexate

Indomethacin, diclofenac (acid) and indomethacin ethyl ester showed low solubility in water, with log D values higher than 2. The formulations were then prepared using drug concentrations higher than their saturation concentration in the aqueous phase. The log D value for indomethacin was similar to that determined for methotrexate ethyl ester, but IndOH-LNC¹ and MTX(OEt)₂-LNC^0.5 were classified as having different types of distribution. On the other hand, the water solubilities of these drugs are slightly different (higher for methotrexate diethyl ester), while those of diclofenac (acid) and methotrexate diethyl ester are similar. Therefore, neither the log D nor the water solubility values can be used exclusively to explain the results. The difference between the distribution of methotrexate diethyl ester and those of indomethacin and diclofenac lies in the chemical nature of the functional groups, which are amines (ammonium) in the former and carboxylic (carboxylate) for the latter two cases. Thus, the results suggested that the drug interacts with PCL by hydrogen bonding, the O–H/O (indomethacin and diclofenac with PCL) interaction being stronger than N–H/O (methotrexate diethyl ester with PCL).

Therefore, in an effort to reduce non-tumor cell toxicity, chemotherapeutic agents better able to localize to tumors, either intrinsically or via attachment to tumor-directing carriers, are being developed. The latter species, often referred to as conjugates, show particular promise and have been shown to increase efficacy or decrease toxicity to non-tumor tissues in several cases. In this work we report the synthesis of conjugates of motexafin gadolinium, an experimental drug demonstrating significant tumor targeting, with methotrexate, a DNA synthesis inhibitor. The resulting conjugates, containing either ester or amide linkers, were tested in vitro for anti-proliferative activity using A549 lung cancer cells. Under conditions involving limited drug exposure times, the ester conjugate exhibited greater activity than the corresponding amide conjugate or methotrexate alone.

High-resolution crystal structures of the enzyme–inhibitor complex have also been elucidated. In particular, the inhibitor methotrexate (MTX) has been studied extensively over the last half century . Methotrexate upon binding to DHFR inhabits the same hydrophobic binding site as folate. Demonstrating a higher binding affinity for DHFR than folate, methotrexate acts as a competitive inhibitor of DHFR. When bound, methotrexate adopts an inverse orientation comparedto that of folate, but retains the same hydrogen bonding geometry as the enzyme–substrate complex. The binding site is configured of the αB helix connecting the αC helix (43–48,lc) to the βC sheet (58–62,lc), and a 9 to 23,lc residue loop (connecting the βA sheet and the αB helix).

In this study, a mixed vesicle of AEPCDA stabilized by vesicleforming surfactant, dimethyldioctadecylammonium chloride (DODAC) was fabricated as a model chromatic polydiacetylene layer, and methotrexate was used as a target material.We employed two types of detecting system in this study. One of the systems involved a simple detection of methotrexate on the exterior by the vesicle solution, whereas the other system involved detection of methotrexate inside the vesicle solution. In the second method, when methotrexate from the interior permeates out of the vesicle, the color of the vesicle can be changed. Fig. 1 shows a schematic color shift of the mixed vesicle during the permeation of methotrexate. This color shift of polydiacetylene layer can be used for the detection of the target material by both adsorption from the outside and permeation from the inside of the vesicle.