BANGOR — Nine years ago, Dimitri Maxim’s mother, Lefki Michael-Maxim, had a kidney transplant. Since the operation, she has had four biopsies to determine whether her body was rejecting the new kidney, she said. Each time, a piece of the organ was removed.

Dimitri, 16, of Carlisle, Mass., didn’t like seeing his mother suffer, so when he was in eighth grade he set out to, “develop a simple, rapid and noninvasive test in patients such as my mother.”

A year and a half later, Dimitri’s invention won him first place at the Maine State Science Fair at Bangor High School.

The invention, which the Gould Academy sophomore said he has submitted for a patent, tests the level of protein in a patient’s blood by inducing a reaction between the blood and other chemicals in a tiny test tube. The color of the liquid in the tube after the reaction indicates whether there is an abnormal level of protein in the blood, a sign that the patient could be rejecting a transplant or have another disease. Other similar mechanisms exist, but Dimitri said his works faster and is cheaper to make.

Michael-Maxim said her son’s genes come from his great-great-grandfather, Hiram Maxim, a Mainer who invented the first portable, automatic machine gun.

Dimitri was one of 150 students from 12 Maine high schools to participate in the science fair on Saturday. The fair was sponsored and organized by the Jackson Laboratory and judged by scientists from that facility, Husson University, the University of Maine and other institutions.

“It’s an amazing opportunity to do an independent research project,” said Joyce Peterson, public information manager at the Jackson Laboratory. “That is the kind of thing that will eventually get you a job at the Jackson Lab.”

Peterson said that nurturing science, math and engineering ability in students is vital to the future of Maine’s economy.

“Jackson Lab has more than 40 positions open,” she said. “We are in great need of young people who want to make their career in science, and we want them to come from Maine.”

Coming in second place were Roger Van Peski, Abby Harvey and Andrew Reilley from the Maine School of Science and Mathematics, and finishing in third place was Dan O’Brien from Bangor High School.

The top three finishers are invited to participate in the Intel International Science and Engineering Fair in May in Los Angeles.

Other projects included a robot on wheels that could sense and navigate around obstacles in its path from Ben Schade and Justin Hamilton of the Maine School of Science and Math and an exploration into using invasive plants to make paper from Bangor High School freshman Willa Thompson.