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Peptides are short chains of amino acids that can interact very specifically with biological targets. Their precision is attractive to researchers, but delivering fragile peptide molecules to the right place, at the right concentration, for the right amount of time is the hard part. Below is a high-level tour of delivery strategies scientists use and why they matter. Nature
Why delivery is a big deal
Unmodified peptides are often rapidly broken down by enzymes and don’t cross biological barriers well (like the gut lining or skin). Contemporary research focuses on formulation and chemical design (e.g., cyclization, lipidation) to improve stability and exposure. Recent reviews summarize the landscape across approved and investigational peptide medicines and vaccines. Nature+1
Injections: the workhorse
Most peptide therapeutics in clinical use are given by subcutaneous or intramuscular injection, which bypasses the gastrointestinal tract and avoids first-pass degradation. Long experience, predictable exposure, and dose flexibility keep injections central even as new routes emerge. State-of-the-field reviews cover barriers (enzymes, clearance) and design tactics that complement parenteral routes. ScienceDirect
Long-acting depots (weeks to months)
To reduce dosing frequency, scientists encapsulate peptides in biodegradable polymers (commonly PLGA) that slowly release drug after injection. This approach underpins several long-acting products and a large research pipeline; current work tunes polymer chemistry, particle size, and fabrication to control release and minimize burst effects. PMC+2MDPI+2
Oral delivery: the SNAC playbook
Oral peptides face two big hurdles—enzymatic degradation and poor permeability. A notable breakthrough is oral semaglutide, which pairs the peptide with SNAC (sodium N-[8-(2-hydroxybenzoyl) amino] caprylate). SNAC locally raises gastric pH and promotes transcellular uptake in the stomach, enabling systemic exposure in humans; mechanistic and clinical reviews detail how this enhancer works. New modeling suggests permeation enhancers can transiently create membrane defects that help polar peptides cross cell layers. PMC+2ScienceDirect+2
Transdermal and microneedles
Standard patches rarely deliver intact peptides, but microneedle arrays (including dissolving microneedles) can painlessly breach the outer skin and release payloads into viable tissue. Recent surveys track advances and remaining translation challenges (robust manufacturing, dose limits, and skin variability). Frontiers+1
Intranasal and other mucosal routes
Intranasal delivery aims to leverage the vascular nasal mucosa (and, for some research programs, nose-to-brain pathways). Success depends on formulation (particle size, mucoadhesives) and avoiding ciliary damage; reviews in peptide/protein delivery discuss both upside and hurdles. ScienceDirect
Antimicrobial peptide (AMP) delivery
AMPS—host-defense peptides that can disrupt microbial membranes—are being paired with nanoparticles and hydrogels to protect them from proteolysis and concentrate activity at infection sites. While much of this work is preclinical, delivery tech is central to unlocking efficacy and safety. BioMed Central+1
Key takeaways
- Delivery often determines whether a peptide concept succeeds; formulation science and chemical tailoring go hand-in-hand. ScienceDirect
- Proven platforms today include injections and long-acting depots; oral, microneedle, and intranasal routes are active areas of innovation. Frontiers+3PMC+3MDPI+3
- For any specific peptide, performance depends on sequence, dose, route, and formulation—not on the term “peptide” itself. Nature
