A surgical instrument is a tool or device for performing specific actions or carrying out desired effects during a surgery or operation, such as modifying biological tissue, or to provide access for viewing it. Over time, many different kinds of surgical instruments and tools have been invented. Some surgical instruments are designed for general use in all sorts of surgeries, while others are designed for only certain specialties or specific procedures. Classification of surgical instruments helps surgeons to understand the functions and purposes of the instruments. With the goal of optimizing surgical results and performing more difficult operations, more instruments continue to be invented in the modern era. History
Many different kinds of surgical instruments and tools have been invented and some have been repurposed as medical knowledge and surgical practices have developed. As surgery practice diversified, some tools are advanced for higher accuracy and stability while some are invented with the completion of medical and scientific knowledge. Two waves in history contributed significantly to the development of surgical tools. In the 1900s, inventions of aseptic surgeries (maintenance of sterile conditions through good hygiene procedures) on the basis of existing antiseptic surgeries (sterilization of tools before, during, and after surgery) led to the manifestations of sale and use of instrument sterilizers, sterile gauze, and cotton. Most importantly,  instruments were advanced to be readily and effectively sterilized by replacing wooden and ivory handles with metals.
δ-Aminolevulinic acid (also dALA, δ-ALA, 5ALA or 5-aminolevulinic acid), an endogenous non-proteinogenic amino acid, is the first compound in the porphyrin synthesis pathway, the pathway that leads to heme in mammals, as well as chlorophyll in plants. 5ALA is used in photodynamic detection and surgery of cancer. Medical uses
As a precursor of a photosensitizer, 5ALA is also used as an add-on agent for photodynamic therapy. In contrast to larger photosensitizer molecules, it is predicted by computer simulations to be able to penetrate tumor cell membranes. Cancer diagnosis
Photodynamic detection is the use of photosensitive drugs with a light source of the right wavelength for the detection of cancer,  using fluorescence of the drug. 5ALA, or derivatives thereof, can be used to visualize bladder cancer by fluorescence imaging. Cancer treatment
Aminolevulinic acid is being studied for photodynamic therapy (PDT) in a number of types of cancer. It is not currently a first line treatment for Barretts esophagus. Its use in brain cancer is currently experimental. It has been studied in a number of gynecological cancers.Aminolevulinic acid is indicated in adults for visualization of malignant tissue during surgery for malignant glioma (World Health Organization grade III and IV). It is used to visualise tumorous tissue in neurosurgical procedures. Studies since 2006 have shown that the intraoperative use of this guiding method may reduce the tumour residual volume and prolong progression-free survival in people with malignant gliomas. The US FDA approved aminolevulinic acid hydrochloride (ALA HCL) for this use in 2017.