Biodegradable polymeric insulin microneedles – a design and materials perspective review

Abstract

Microneedle (MN) delivery devices are more accepted by people than regular traditional needle injections (e.g. vaccination) due to their simplicity and adaptability. Thus, patients of chronic diseases like diabetes look for alternative pain-free treatment regimens circumventing regular subcutaneous injections. Insulin microneedles (INS-MNs) are a thoughtfully researched topic (1) to overcome needle phobia in patients, (2) for controlled delivery of the peptide, (3) decreasing the frequency of drug administration, (4) to ease the drug administration procedure, and (5) thus increasing patient adherence to the treatment dosage regimes. MNs physically disrupt the hard outer skin layer to create minuscule pores for insulin (INS) to pass through the dermal capillaries into the systemic circulation. Biodegradable polymeric MNs are of greater significance for INS and vaccine delivery than silicon, metal, glass, or non-biodegradable polymeric MNs due to their ease of fabrication, mass production, cost-effectiveness, and bioerodability. In recent years, INS-MNs have been researched to deliver INS through the transdermal implants, buccal mucosa, stomach wall, intestinal mucosal layers, and colonic mucosa apart from the usual transdermal delivery. This review focuses on the design characteristics and the applications of biodegradable/dissolvable polymeric INS-MNs in transdermal, intra-oral, gastrointestinal (GI), and implantable delivery. The prospective approaches to formulate safe, controlled-release INS-MNs were highlighted. Biodegradable/dissolvable polymers, their significance, their impact on MN morphology, and INS release characteristics were outlined. The developments in biodegradable polymeric INS-MN technology were briefly discussed. Bio-erodible polymer selection, MN fabrication and evaluation factors, and other design aspects were elaborated.

Graphical Abstract

Keywords:

• Diabetes
• transdermal insulin delivery
• oral insulin microneedles
• biopolymeric insulin microneedles
• implantable insulin microneedles
• non-parenteral insulin delivery

Acknowledgements

Figures were created with BioRender.com and Canva. The authors would like to thank the UCSI University and INTI International University – Library facilities, Malaysia for their electronic data support for this review article.

Author contributions

M.S.C.: conceptualized, designed the outline, and drafted the original draft of the review article; S.M. and Z.M.S.: conceptualized, supervision, critiqued, reviewed, and edited; A.K.J.: conceptualized, critiqued, funding acquisition, reviewed, and edited; R.S. and C.S.K.: critiqued, reviewed, and edited; C.W.H.: funding acquisition, reviewed, and edited; H.N.A. and A.R.H.: provided intellectual input during the reviewing and editing; N.M.H.: supervision, reviewed, and edited. All authors have read and agreed on the finalized version.

Disclosure statement

None of the authors have any conflicts of interest to disclose.

Data availability statement

Data sharing is not applicable to this article as no new data were created or analyzed in this review.

Additional information

Funding

The authors thank the Ministry of Education, Malaysia, for providing the Fundamental Research Grant Scheme (FRGS) Grant Number: FRGS/1/2021/SKK0/UM/02/7, and Universiti Malaya for the support.