Biodegradable Porous Microneedles for an Electric Skin Patch

Abstract

An array of porous microneedles (PMNs) made of biodegradable poly(lactic-co-glycolic acid) (PLGA) is fabricated by a combination of molding and freeze-drying methods. The optimized mixture of PLGA and 1,4-dioxane is poured into a mold of a microneedle array, followed by the freezing and sublimation of the frozen particles of 1,4-dioxane, a procedure that left an interconnecting porous structure in the PLGA with a porosity around 50%. The mechanical strength of the PMN made of PLGA (PLGA-PMN) is reinforced by modification with carboxymethylcellulose (CMC), resulting in sufficient strength enough for insertion into an excised porcine skin. The transdermal resistance is significantly decreased by the CMC-modified PLGA-PMN, which would improve the efficiency and safety of DC current-based transdermal techniques, including the electrical monitoring of the skin condition and iontophoresis for drug delivery and medical diagnosis.

Porous Microneedles for Therapy and Diagnosis: Fabrication and Challenges

“…61 By successfully preparing PLGA-pMNs using this method (Figure 8B), PLGA-pMNs modified with carboxymethyl cellulose (CMC) can be inserted into the skin to form transdermal ionic connections, enabling electrical monitoring of skin conditions as well as medical diagnosis and drug delivery via transdermal iontophoresis. 16 Pore size and porosity are impacted by freeze-drying process variables like freezing temperature and solute content. In large part, the freezing temperature determines the pore diameter.…”

“…Another study 60 discovered that plasma treatment enhanced the extraction speed of pMNs. However, in some experiments, 16 the plasma treatment did not produce satisfactory results, and deformation of the MNs was observed when the researchers overtreated with oxygen plasma. Because of these issues with plasma treatment, it has been proposed to improve the hydrophilicity of material surfaces by coating them with biocompatible surfactants or grafting them with hydrophilic polymers.…”

“…The way to reduce the overall porosity of the MNs or only introduce pores into a specific part of the needle body is to improve the mechanical properties of the pMNs by adjusting the porosity in the MNs. ,, However, these two ways will lead to a reduction in the drug load, which is not expected for drugs that require high doses to function. The coating ,− can improve the mechanical strength of the MNs without decreasing porosity, and it can also act as a drug carrier to improve the drug loading of the MNs. It should be noted that the coating must select the appropriate coating formula and coating process to avoid the coating’s impact on the sharpness of the MNs and the piercing effect.…”

Advances of Microneedles in Biomedical Applications

“…Polymers are highly viscous, not prone to fracture, and are mostly biocompatible and suitable for low-cost mass production [49], which has been extensively used to fabricate microneedles for biomedical applications. Several biocompatible materials have been developed for microneedle fabrication, such as carboxymethyl cellulose (CMC) [50], PVA, polyvinylpyrrolidone (PVP), poly (lactic-co-glycolic acid) (PLGA) [51], hyaluronic acid (HA), methacrylated hyaluronic acid (MeHA) [52] and so on. Mao et al loaded poorly water-soluble rapamycin into PVP MN, as PVP can help rapamycin dissolve quickly in the body.…”

Anti-SARS-CoV-2 IgM/IgG antibodies detection using a patch sensor containing porous microneedles and a paper-based immunoassay

“…Porous MNs have been developed within a decade for collecting the dermal ISF whereas various biocompatible and biodegradable polymers have been successfully used to fabricate of porous structures 42 . The ISF extraction can be realized by capillary action owing to micron-sized porous structures and moreover, lab-on-chips biosensing device can be directly affixed to the porous MNs for subsequent analysis and disease diagnosis 31 , 43 . Therefore, an immunoassay biosensor can be designed and integrated with porous MNs for simple and rapid detection of IgM and IgG antibodies against SARS-CoV-2 in the ISF.…”