What is the ruling on researching the prolongation of human biological life, and is one who wishes to live a long life in a healthy body sinful?

There is no objection to permissible medical research aimed at combating diseases of old age and legitimate treatment, for caring for one's health is a Shari objective, and there is no harm in desiring a long life coupled with good deeds. As for research related to "rejuvenation," it is not science, for Allah created man in stages of weakness, then strength, then weakness and old age, and this is a cosmic law that does not change. Senescence is the destiny of one whom no disease has destroyed.