Requirements: 1. Maintain the original format and structure. 2. The translation should be accurate, fluent, and natural. 3. Maintain professionalism and consistency. 4. Only return the translation result; do not add any explanations. Original text: In the field of anti-aging, AKG (alpha-ketoglutaric acid) and AKG-Ca (calcium alpha-ketoglutarate) are becoming the new favorites. They can activate cellular energy cycles, improve metabolic efficiency, and extend healthy lifespan. However, their challenges are also evident: poor molecular stability, easy inactivation in the acidic stomach environment, and the need for long-acting sustained release to maintain blood drug concentrations. At this point, three delivery technologies—microspheres, microcapsules, and nanosystems—have quietly sparked a “revolution in in-body drug delivery,” helping AKG evolve from a “bare” substance to a more sophisticated form. How do these technologies protect and enhance the effectiveness of AKG? **Microspheres:** Defined as spherical entities with a diameter of less than 2.5 mm, made by processes such as extrusion and spheronization or centrifugal granulation, microspheres ensure a uniform distribution of the active ingredient. Features: Each microsphere acts as an independent release unit, increasing bioavailability by 30%. They can also be designed for sustained-release, providing stable, controllable, and efficient drug delivery. Applications: Suitable for tablet manufacturing, hard capsules, soft capsules, and solid beverages. For example, AKG microspheres disintegrate quickly in the stomach, releasing their peak dose within 30 minutes, making them ideal for rapid energy replenishment after exercise. When combined with B vitamins and electrolytes, they can significantly enhance anti-fatigue effects. **Microspheres (long-acting energy banks):** AKG is evenly dispersed within a degradable polymer matrix (such as PLGA), forming nano- or microscale spheres. Characteristics: Despite their small size, they have a large surface area. AKG is released slowly as the material degrades, similar to raisins embedded in bread. Applications: Widely used in long-acting sustained-release injections. For instance, PLGA microspheres can regulate the degradation rate, allowing for continuous AKG release over 14–30 days, eliminating the need for daily oral doses. **Microcapsules:** Liquid or solid AKG is encapsulated in a polymer membrane (such as gelatin or chitosan), creating a core-shell structure with particle sizes ranging from 1 to 1000 μm. Features: The outer shell protects the AKG from light, oxygen, and stomach acid, preserving its activity. The release site can be controlled by the thickness and material of the membrane (e.g., for enteric release). Applications: Utilized in high-end skincare products due to their high transdermal absorption and UV protection. **Core differences in delivery technologies:** - **Structure and release logic:** - **Microspheres:** Homogeneous entities that disintegrate and release the active ingredient quickly (0.5–2.5 mm in diameter). - **Microspheres (degradable type):** The active ingredient is combined with a matrix, and the entire structure degrades to release the drug over time (1–250 μm in diameter). - **Microcapsules:** The active ingredient is separated from the shell, with the shell controlling the release site (e.g., through membrane permeability, for enteric release, 1–1000 μm in diameter). **Which “delivery courier” does your body need?** - For quick energy replenishment after exercise or post-meal metabolism? Choose microspheres. - For long-term anti-aging effects or chronic disease management? Choose microspheres. - For transdermal delivery or for those sensitive to stomach acid? Choose microcapsules. **Options:** - Microspheres - Microspheres - Microcapsules