本研究以一具有 pH 敏感及溫度敏感特性之聚胺基酸水膠 mPEG-p(Ala)-p(Lys)(methoxy-poly(ethylene glycol)-poly(L-alanine)-poly(L-lysine)) 作為口服藥物奧曲肽載體，探討其成膠性質及其在藥物投遞應用上之潛力。將 methoxy-poly(ethylene glycol)(mPEG)末端的-OH 改質為-NH2 後與 NCA-alanine 進 行開環聚合形成 mPEG-p(Ala)，接著與不同比例之 L-lysine(Z)進行第二次開環聚 合，並切除保護基，形成具 pH 敏感特性的 mPEG-p(Ala)-p(Lys)，欲探討不同長 度的 p(Lys)鏈段對藥物釋放的效果差異。
此材料經由 NMR、GPC 及 FTIR 鑑定證實合成成功，其高分子水溶液可形成 微胞，臨界微胞濃度介於 0.03~0.068 wt%，微胞粒徑大小約為 60~90 nm。以倒置 法測試材料之成膠性質，結果顯示依不同 p(Lys)鏈段長度，約在 14~15 wt%可在 20~25°C下成膠。材料表面結構呈現三維網狀結構，具有足夠大小與空間提供藥 物包覆及水份通透性。Zeta potential 結果顯示隨環境 pH 值下降，p(Lys)質子化程 度較高因此有較高的表面電位。水膠含水率及膨潤率則隨 p(Lys)鏈段長度的增加 及環境 pH 值的下降而增加。水膠降解測試則表明具較長 p(Lys)鏈段之水膠較易 降解產生重量損失，進而影響藥物釋放結果。此材料包覆奧曲肽之包覆率可達 97% 以上，可將投入之藥物完整包覆在水膠材料當中。體外釋放結果顯示 L10 因降解 快速可在兩天內釋放 98%的藥物總量，較 L2 的 74%來得多，但其在體外生物毒 性測試有較低的生物相容性，因此在應用上 L2 水膠會是較佳的選擇。綜合以上 結果表明 mPAL 水膠材料在作為口服藥物載體應用及藥物控釋上具一定潛力。

In this study, a pH/thermo-sensitive polypeptide hydrogel methoxy-poly(ethylene glycol)-poly(L-alanine)-poly(L-lysine)(mPEG-p(Ala)-p(Lys)) with different length of poly(L-lysine) was synthesized and used as a drug carrier of the octapeptide drug, octreotide. The -OH group on methoxy-poly(ethylene glycol)(mPEG) was first modified to -NH2, and NCA-Ala was co-polymerized with mPEG at the N-terminal end by ring-opening polymerization to form mPEG-p(Ala). Afterwards, mPEG-p(Ala) was co-polymerized with NCA-Lysine and the protecting groups were removed to form mPEG-p(Ala)-p(Lys). The effect of different p(Lys) segments on drug release behavior was investigated.
The structure and molecular weight of the polymer were analyzed by NMR, FTIR and GPC. The polymer with different length of p(Lys), L2 and L10, could form gel at a concentration of 14~15 wt% at 22~24°C. The three-dimensional network structure of the hydrogel was observed by SEM, providing drug encapsulation space and water permeability. The zeta potential of mPAL increased as the pH decreased due to different protonation degree of the p(Lys) segment. The water content and swelling ratio were higher when the p(Lys) segment was longer and the pH value was lower. Hydrogel with longer p(Lys) segment also had higher degradation rate, influencing the drug release properties. The drug encapsulation efficiency could approach 97~99% for both L2 and L10. The results of in vitro release showed that L10 could release most of the encapsulated octreotide in 2 days due to its fast degradation, but L2 could only release 74%. Though L10 had better controlled release behavior in gastrointestinal digestive system but it had lower cell compatibility than L2. Thus, L2 might be a better choice for delivering oral Octreotide. Based on aforehand results, mPAL hydrogel shown to have a good potential in oral drug delivery and controlled release.

1. Kowalski, P. S., Bhattacharya C., Afewerki S., Langer R. Smart biomaterials: recent advances and future directions. ACS Biomater. Sci. Eng. (2018), 4, 3809−3817.
2. Wichterle, O., Lím, D. Hydrophilic gels for biological use. Nature (1960), 185, 117–118.
3. Lim F, Sun AM. Microencapsulated islets as bioartificial endocrine pancreas. Science. (1980), 210(4472):908-10.
4. Yannas IV, Lee E, Orgill DP, Skrabut EM, Murphy GF. Synthesis and characterization of a model extracellular matrix that induces partial regeneration of adult mammalian skin. Proc Natl Acad Sci USA. (1989), 86(3), 933-937.
5. Samson S. L. et al. Maintenance of acromegaly control in patients switching from injectable somatostatin receptor ligands to oral octreotide, J. Clin. Endocrinol. Metab, (2020), 105(10), 526.
6. Ghobril C., Grinstaff M. W. The chemistry and engineering of polymeric hydrogel adhesives for wound closure: a tutorial. Chem. Soc. Rev. (2015), 44, 1820-1835.
7. Yu L., Chang G., Zhang H., Ding J., Temperature-induced spontaneous sol-gel transitions of poly(D,L-lactic acid-co-glycolic acid)-b-poly (ethylene glycol)-b-poly(D,L-lactic acid-co-glycolic acid) triblock copolymers and their end-capped derivatives in water. J. Polym. Sci. A Polym. Chem. (2007), 45(6), 1122-33.
8. Goonoo N., Bhaw-Luximon A., Ujoodha R., Jhugroo A., Hulse G.K., Jhurry D. Naltrexone: a review of existing sustained drug delivery systems and emerging nano-based systems. J Control Release. (2014), 183, 154-66.
9. Atul R. K., Nikolaos A. P., Swelling/deswelling of anionic copolymer gels. Biomaterials. (1995), 16, 559-567.
10. Rizwan M., Yahya R., Hassan A., Yar M., Azzahari A.D., Selvanathan V., Sonsudin F., Abouloula C.N., pH sensitive hydrogels in drug delivery: brief history, properties, swelling, and release mechanism, material selection and applications. Polymers. (2017), 9(4), 137.
11. Jessica C. G., Allan S. H., Patrick S. S., Injectable pH- and temperature-responsive poly(n-isopropylacrylamide-co-propylacrylic acid) copolymers for delivery of angiogenic growth factors. Biomacromolecules. (2010), 11 (7), 1833-1839.
12. Bolla P. K., Rodriguez V. A., Kalhapure R. S., Kolli C. S., Andrews S., Renukuntla J. A review on pH and temperature responsive gels and other less explored drug delivery systems. J. Drug. Deliv. Sci. Tec. (2018), 46, 416–435.
13. Ward, M.A.; Georgiou, T.K. Thermoresponsive Polymers for Biomedical Applications. Polymers. (2011), 3, 1215-1242.
14. Lin CC, Metters AT. Hydrogels in controlled release formulations: network design and mathematical modeling. Adv Drug Deliv Rev. (2006), 58(12-13), 1379-408.
15. Amsden B. Solute diffusion within hydrogels. Mechanisms and models. Macromolecules. (1998), 31(23), 8382-8395.
16. Siepmann, J. Modeling of drug release from delivery systems based on hydroxypropyl methylcellulose (HPMC). Adv Drug Deliv Rev. (2001), 48, 139-157.
17. Fosgerau K., Hoffmann T. Peptide therapeutics: current status and future directions. Drug Discov Today. (2005), 20(1), 122-128.
18. Li Y., Duan Z., Tian Y., Liu Z., Wang Q.. A novel perspective and approach to intestinal octreotide absorption: sinomenine-mediated reversible tight junction opening and its molecular mechanism. Int. J. Mol. Sci. (2013), 14(6), 12873-12892.
19. Drucker, D.J. Advances in oral peptide therapeutics. Nat. Rev. Drug. Discov. (2020), 19, 277–289.
20. Shaji J, Patole V. Protein and Peptide drug delivery: oral approaches. Indian J Pharm Sci. (2008), 70(3), 269-277.
21. Choonara B. F. et al. A review of advanced oral drug delivery technologies facilitating the protection and absorption of protein and peptide molecules. Biotechnol. (2014), 32(7), 1269-1282.
22. Lamberts, S.W.J., Van Der Lely A. J., De Herder W. W., Hofland L. J. Octreotide. N Engl J Med. (1996), 334, 246-254.
23. Bauer W. et al. A very potent and selective octapeptide analogue of somatostatin with prolonged action. Life Sci. (1982), 31(11), 1133-40.
24. Giustina A, Karamouzis I, Patelli I, Mazziotti G. Octreotide for acromegaly treatment: a reappraisal. Expert Opin Pharmacother. (2013), 14(17), 2433-47.
25. Newman C.B. et al. Octreotide as primary therapy for acromegaly. J Clin Endocrinol Metab. (1998), 83(9), 3034-40.
26. Battershill P.E., Clissold S.P., Octreotide. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in conditions associated with excessive peptide secretion. Drugs. (1989), 38(5), 658-702.
27. Maria S. et al. Synthesis and characterization of pre-activated thiolated chitosan nanoparticles for oral delivery of octreotide. J. Drug. Deliv. Sci. Tec. (2020), 58, 101807.
28. Ghassemi A.H. et al. Controlled release of octreotide and assessment of peptide acylation from poly(D,L-lactide-co-hydroxymethyl glycolide) compared to PLGA microspheres. Pharm Res. (2012), 29(1), 110-20.
29. Beschiaschvili G., Seelig J., Peptide binding to lipid membranes. Spectroscopic studies on the insertion of a cyclic somatostatin analog into phospholipid bilayers. Biochim Biophys Acta Biomembr. (1991), 1061, 78-84.
30. Fricker G, Drewe J, Vonderscher J, Kissel T, Beglinger C. Enteral absorption of octreotide. Br J Pharmacol. (1992), 105(4), 783-786.
31. Melmed S. et al., Safety and efficacy of oral octreotide in acromegaly: results of a multicenter phase III trial. J Clin Endocrinol Metab. (2015), 100(4), 1699-708.
32. Maggio E.T., Grasso P. Oral delivery of octreotide acetate in Intravail® improves uptake, half-life, and bioavailability over subcutaneous administration in male Swiss webster mice. Regul Pept. (2011), 167(2-3), 233-8.
33. Ljubimov A. V., Boulton M. E., Caballero S., Grant M. B., Antagonism of the Growth Hormone Axis as a Therapeutic Strategy for Diabetic Retinopathy, Diabetic Retinopathy (2008), 449-463.
34. Sidéris L., Dubé P., Rinke A. Antitumor effects of somatostatin analogs in neuroendocrine tumors. Oncologist. (2012), 17(6), 747-55.
35. Abdel-Rahman O., Lamarca1 A., Valle J. W., Hub R. A. Somatostatin receptor expressionin hepatocellular carcinoma: prognostic and therapeutic considerations. Endocr.-Relat. Cancer. (2014), 21, 485-493.
36. Byeongmoon J., You H. B., Sung W. K., thermoreversible gelation of PEG-PLGA-PEG triblock copolymer aqueous solutions. Macromolecules (1999), 32, 7064-7069.
37. Alica K., Krzysztof S., Agnieszka C., Joanna B., Monika B., In vitro toxicity studies of biodegradable, polyelectrolyte nanocapsules. Int. J. Nanomedicine (2018), 13, 5159-5172.
38. Janeesh P. A., Haider S., Dhanya C. R., Sri S., Annie A., Immunocompatibility and toxicity studies of Poly-L-Lysine nanocapsules in Sprague–Dawley rats for drug-delivery applications. Chem Biol Drug Des. (2014), 84, 292-299
39. Khuloud T. Al-Jamal, Wafa’ T. Al-Jamal, Julie T.-W. Wang, Noelia R., Joanna B., David G., Mire Z., Kostas K., Cationic poly-l-lysine dendrimer complexes doxorubicin and delays tumor growth in Vitro and in Vivo. ACS Nano, (2013), 7 (3), 1905-1917.
40. Khuloud T. Al-Jamal, Wafa’ T. Al-Jamal, Simon A., Jennifer E. Podesta, Açelya Y., John A. Turton, Alberto B., Neil V., Chryso K., Alexander T. Florence, Gillian M. Tozer, Kostas K., Systemic antiangiogenic activity of cationic poly-L-lysine dendrimer delays tumor growth. PNAS., (2010), 107(9), 3966-3971.