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Figure 2. Biological metabolic pathways and sensing strategy selection. (A and B) Metabolic processes in the human body; (A) Schematic illustration of major target organs associated with key biomarkers: (1) liver, (2) muscle, and (3) kidney; (B) Metabolic flow map of glucose, creatine, and lactate. These pathways illustrate the dynamic interactions between organ-specific metabolism and systemic physiological environments; (C) Relationship between biomarker molecular mass, PK dynamics, physiological turnover, and the resulting need for continuous monitoring; (D) Decision-making framework for selecting optimal sensing strategies based on the physicochemical and physiological profiles of target biomarkers. PK: Pharmacokinetic; NAD+: nicotinamide adenine dinucleotide (oxidized form); NADH: nicotinamide adenine dinucleotide (reduced form); LDH: lactate dehydrogenase; SAH: S-adenosyl-L-homocysteine; SAM: S-adenosyl-L-methionine; GAA: guanidinoacetate; GAMT: guanidinoacetate N-methyltransferase; AGAT: arginine: glycine amidino transferase.