Clinical Benefit and Safety of Microneedle Patches Composed of Magnesium: A Pilot Study in Acne Patients

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Introduction
In the biomedical realm, metallic materials such as stainless steel, cobalt, and titanium have traditionally been used as implants.In addition, biodegradable metal implants are in development.Magnesium (Mg), iron, and zinc are the new generation of biodegradable materials and have been actively evaluated [1].Mg and Mg-based alloys are widely used materials in the medical feld especially in orthopedic and cardiovascular departments [2,3].Using Mg as a biomaterial has several advantages.First, Mg naturally corrodes in the physiological environment.Second, intermediate corrosion products in the Mg corrosion process, such as Mg 2+ ions, H 2 gas, and OH − , are absorbable or physiologically present in the human body.Terefore, no toxicity has been reported.
As Mg is a highly reactive metal, it dissolves in water with the following reaction: (1) During this corrosion process, Mg generates hydrogen [4,5].Molecular hydrogen has been known to function as an antioxidant and anti-infammatory agent.Previous studies delivering hydrogen by inhalation, intravenous injection, or water supplement have reported a therapeutic efect of hydrogen in the wound healing process [6].A study on a hydrogen-generating patch made of aluminum and calcium hydroxide demonstrated that hydrogen improved the viability of skin cells, promoted cellular migration, and enhanced collagen expression level [7].
Moreover, Mg is thought to have an antibacterial property.Robinson et al. [8] demonstrated in an in vitro study that Mg metal inhibited the growth of E. coli, P. aeruginosa, and S. aureus.In 2018, a halo test of a magnesium microcarrier against Cutibacterium acnes (C.acnes) was performed by the Korea Testing and Research Institute, and the results revealed that the magnesium microcarrier also has an antibacterial efect against C. acnes, which plays an important role in infammatory acne lesions [8,9].
Acne vulgaris is a common concern in patients in their 20 s and 30 s [9,10].Te frst-line treatment for mild to moderate acne patients includes application of topical retinoid, antibiotic, benzoyl peroxide, and azelaic acid [9].Tese topical agents may cause irritation, scaling, and erythema, which can be a drawback for persistent use.Longterm application of topical antibiotics may carry another worrisome issue-that of antibiotic resistance.Terefore, other alternative treatment modalities have been studied and one of them, microneedling, has been introduced in the clinical feld [9][10][11][12].
A microneedle (MN) is a minimally invasive appliance that shows efects through skin microinjuries and micropuncturing [11][12][13][14].It has been efectively used in various skin diseases such as scars, acne, melasma, and skin rejuvenation.Te efects of MN on skin may vary depending on material and needle characteristics and the active medicinal agent transmitted by transepidermal delivery.Based on the length and thickness of the needles, MNs can be used as noninvasive home skin care devices.Te MN used in cosmetic procedures conducted by doctors in the clinic are between 0.5 and 3 mm in length, with a diameter between 0.1 and 0.25 mm, which can penetrate the papillary dermis down to the mid-dermis based on the average skin thickness of adults [11][12][13].As a home device, an MN less than 0.5 mm in length cannot reach into the dermis; in general, it does not result in hemorrhages or severe skin injuries.
Various materials including metal, silicon, and polymer are used to create MN patches [11,15].Conventional MNs used in acne and acne scars are mostly composed of stainless steel as a physician-applied device.Stainless steel is not suitable for a home-based device or as a form of patch because of irritation and possible allergic reaction [16].Other MN patches for individual uses at home are made of bioabsorbable needles that accelerate topical delivery of active agents only and cannot mimic the role of microneedling itself [10].
MN patches composed of microneedles made of Mg metal with a needle length of 0.25 mm in a hydrocolloid band were newly developed considering the biomedical efects of Mg and MN itself.Tey are expected to improve infammatory acne lesions and prevent acne scarring when applied as a home-based device.Benefcial efects on widened pores, which are a common accompanying issue for acne patients, can also be expected due to their needling efect and the Mg-induced wound healing process.However, there have been no clinical studies about the efcacy and safety of Mg MN patches in patients with mild to moderate acne.Terefore, this pilot study was designed to investigate the safety and efectiveness of Mg MN patches as home use devices for infammatory acne lesions and widened pores.

Materials and Methods
Tis clinical trial was approved by the Institutional Review Board of Samsung Medical Center, Sungkyunkwan University School of Medicine in Seoul, Korea (IRB approval no.SMC 2020-12-020).Tis study has been registered in Clinical Research Information Service (https://cris.nih.go.kr,KCT0007663).Te study was conducted according to the protocols of the Declaration of Helsinki.

Patients.
Patients with mild to moderate acne and between the ages of 20 and 40 years were recruited prospectively.Written informed consent was obtained before the study began.Te severity of acne vulgaris was determined with the Korean Acne Grading System (KAGS) [17].Te exclusion criteria were as follows: patients who were taking any oral medication for acne treatment; women who were pregnant or lactating; patients who had been treated with botulinum toxin, ultrasound, or laser within six months; patients who had been treated with hyaluronic acid fller within one year; and patients who were using other drugs that might impact the efect of magnesium.Patient recruitment and allocation in the study is described in Figure 1(a).

Devices.
Te patch used in this study was a spot patch with Mg MNs on the hydrocolloid band for infammatory acne lesions, and the patch was modifed for the nose and pores of both cheeks; the patches are market-available and in use.Te patch has multiple Mg microneedles of 0.25 mm in length (Figure 2).

Study Protocols.
Patients were instructed to apply Mg MN spot patches once a day for papules, pustules, and nodules after washing in the evening.After eight hours of use, the patches were removed.Te Mg MN spot patches were applied every night until the lesions improved.Patients were also advised to apply Mg MN pore patches to the nose and both cheeks every other night for two hours during the study period.Patients were followed for 12 weeks after starting the use of Mg MN patches.During the study period, patients were not allowed to change their daily cosmetics, including facial washes, or to use topical antiacne medication.

Clinical Assessments.
At the baseline visit and on days three and seven, clinical photographs of patients were obtained to evaluate the efect of Mg MN patches on infammatory acnes.Papules, pustules, and nodules were counted separately by an independent investigator.In this study, a discretionally calculated acne score was used to evaluate the changes in lesions over time.Two points each 2 Dermatologic Terapy were assigned for papules, four points each for pustules, and six points each for nodules, and one point was deducted when the size of the lesion decreased or improved; for example, from pustule to papule or papule to fat erythema.New lesions occurring after the initial evaluation at baseline were excluded from the count because the evaluation focused on the clinical course of infammatory acne when using Mg MN patches on the lesions.Te pore sizes and sebum and porphyrin levels of volunteers were evaluated by using a face analyzer (Mark-Vu; PSI PLUS, Daejeon, Korea) at weeks zero, four, and twelve.Researchers checked patient compliance by individual phone calls once a week, giving an explanation of instruction and asking if they are following it well.Te study design of this clinical trial is described in Figure 1(b).
To assess safety, questionnaires about subjective adverse reactions such as pruritus, burning, tingling, and pain and objective adverse reactions such as redness, edema, papules, scales, and pigmentation were obtained at each visit.

Statistical Analysis.
Te researchers used generalized estimating equations to determine changes over time compared to baseline.Statistical signifcance was defned as p value <0.05.All statistical analyses were conducted by two biostatistics specialists (SW Kim and JS Shim).Dermatologic Terapy 3

Demographics.
Patients with mild to moderate acne vulgaris with a Korean Acne Grading System (KAGS) [17] score less than 3 were included in the study (Table 1).A total of 19 patients were enrolled, and the mean age of patients was 31.5 years (age range: 23-38 years).Four patients were male, and 15 patients were female.

Efcacy on Infammatory Acne Lesions.
Te average number of acne lesions during the study continuously decreased from 3.06 at baseline to 1.11 after three days and 0.61 after seven days (p value <0.001).Furthermore, the average acne score calculated in this study decreased from 8.22 at baseline to 2.5 on day three and 1.5 on day seven (p value <0.001).Te detailed scores of every subject decreased compared to baseline scores, except for Subject 1 and Subject 19 (Table 2).A GEE analysis was performed to observe the changes over time and showed that the number of infammatory acne lesions and acne scores decreased over seven days (Table 3, Figures 3 and 4).

Efcacy on Pore Sizes, Sebum Secretion, and Porphyrin
Counts.Te mean size of pores on the nose and measured by using a facial analyzer was 43.95 at baseline, 44.79 after four weeks, and 46.47 after 12 weeks of every other night use (Table 4).Tis increase in size was statistically signifcant.
Te mean size of pores on cheeks was 94.79 at baseline, 94.00 after four weeks, and 93.12 after 12 weeks, which showed no signifcant diference (Figure 5(a)).Te mean sebum secretion of the nose, measured by using the facial analyzer, was 17.26 at baseline, 17.47 at week four, and 17.82 at week 12, with no signifcant diference (p value � 0.77).Te mean sebum secretion of both cheeks showed a decrease after using a Mg MN patch (23.00 at baseline, 20.74 at week four, and 19.47 at week 12, but no signifcant diference (p value � 0.16) (Figure 5(b)).
Te mean porphyrin levels of the nose and cheeks showed a tendency to decrease over time (nose: 40.47 at week zero, 36.63 at week four, and 34.41 at week 12; both cheeks 43.16 at week zero, 35.89 at week four, and 39.12 at week 12, respectively) A statistically signifcant decrease was noticed in both cheeks at week four compared with baseline (p value � 0.002) (Figure 5(c)).

Adverse Efects.
No noticeable side efects such as redness, edema, papules, scales, and pigmentation were observed during the study period.No subjects reported any subjective adverse reactions like pruritus, burning, tingling   Dermatologic Terapy sensation, and pain.Interestingly, no patients reported any acne scarring on the lesions where Mg MN patches were applied.

Discussion
Tis study found that the Mg MN patch reduced acne lesions within a few days, even when patients did not take antiacne medications or apply topical antiacne agents.Tis rapid improvement of infammatory acne in days is a remarkable fnding considering the clinical evidence and previous reports that showed it takes weeks for topical application of retinoid and other agents to improve infammatory acne lesions [18].Changes in acne scores, which refect the time efect of Mg MN patches, implied that simple application of Mg MN patches on infammatory acnes for eight hours  Tis study has its own value through observation of courses of infammatory acne using Mg MN patches.It is difcult to provide patient follow-up in the clinical setting as frequently as in this study.Follow-up was performed at baseline, three days, and seven days after using Mg MN patches, and the changes in infammatory acne lesions were evaluated.As the results showed, the infammatory improved days after application of the Mg MN patch without any serious adverse events.
Acne patients often complain of widened pores and excessive sebum production.Initial uses of MN were targeted to improve skin texture, wrinkles, and atrophic scars.Terefore, the safety and efcacy of Mg MN patches on pores and sebum production were also analyzed.Unexpectedly, the pore size and sebum secretion of the nose increased at follow-up visits.On the contrary, that of both cheeks tended to decrease at weeks four and twelve compared with baseline, although they failed to show statistically signifcant diferences.Two major causes could be considered for an unsatisfactory efect on pore size and sebum secretion.First, facial pores and sebum secretion are easily afected by exogenous factors.In some patients, the study was conducted in spring and summer, when the size of the pores might have been infuenced by environmental factors [9].To improve enlarged pores, it is essential that the dermis be sufciently stimulated by needling to induce collagenesis [11,15].Te length of the needles used in this study (0.25 mm) might be insufcient to show noticeable clinical efects on pore size.Adjusting the needle length, increasing use time, or using a combination of topical agents combined with MNs that can promote collagen synthesis might also be ways to increase the therapeutic efect on enlarged pores and sebum secretion.
For porphyrin level, a substantially signifcant reduction of both cheeks was observed.Te porphyrin level of the nose also showed a tendency to decrease during the study period.Tis result also supported the inhibitory efect of Mg MNs against C. acnes, which produces porphyrin as a metabolite [19].
A limitation of this study was that there was no control group, as it was conducted as an exploratory study for evaluation of the safety and efcacy of newly developed Mg MN patches as a home care device.However, to the best of the authors' knowledge, this is the frst research to explore the efcacy and safety of Mg MNs on infammatory acne lesions and to observe changes occurring over days using Mg MN patches.Study fndings showed defnite improvement of infammatory acne lesions after using Mg MN patches over days, and this study may provide a basis for further studies about dermatologic uses of Mg MNs.

Conclusion
In conclusion, Mg MN patches with multiple needles 0.25 mm in length can improve acne lesions within a few days and are demonstrated to be safe to use as a home care device for at least 12 weeks.To be efective in reducing pore size and sebum secretion with Mg MN patches 0.25 mm in length, changes in the formulation, method of application, or combination of topical agents for transdermal delivery could be contemplated.MNs with longer needles may provide more beneft for reduction of pores.Further randomized controlled studies with a larger number of patients and a longer follow-up period are required.

Data Availability
Datasets for this research are available on request from the corresponding author.Due to privacy and ethical concerns, details of the data are not publicly available.

Disclosure
Tis research has been provided as a preprint in the Research Square and Europe PMC in the following links: https://www.researchsquare.com/article/rs-1866277/v1and https:// europepmc.org/article/ppr/ppr547393.

Figure 3 :Figure 4 :
Figure 3: (a) Changes in total number of acne lesions over time and (b) changes in acne scores over time (p values less than 0.05 shown as * less than 0.01 shown as * * and less than 0.001 shown as * * * ); visit 1: day zero, visit 2: day three, visit 3: day seven.

Figure 4 :
Figure 4: Clinical photographs: (a) patient 6 at baseline, (b) patient 6 at day three, (c) patient 6 at day seven, (d) patient 8 at baseline, (e) patient 8 at day three, and (f ) patient 8 at day seven.

Figure 5 :
Figure 5: (a) Changes in pore sizes of the nose and both cheeks over time, (b) changes in sebum secretion of the nose and both cheeks over time, and (c) changes in porphyrin level of the nose and both cheeks over time (p values less than 0.05 shown as * less than 0.01 shown as * * and less than 0.001 shown as * * * ); visit 1: week zero, visit 4: week four, visit 5: week twelve.

Table 2 :
Detailed scores of acne lesions of subjects.All subjects except 1 and 19 showed a decrease in acne scores.Of the 19 volunteers, 18 were analyzed because the clinical photos of one subject (subject 15) were not sufcient.

Table 3 :
Changes in the number of acne lesions and acne scores over time.Te total number of acne lesions and acne scores decreased signifcantly.p value is corrected by Bonferroni correction.

Table 4 :
Changes in pore sizes, sebum secretion, and porphyrin level of the nose and both cheeks over time.Te mean size of pores of the nose increased signifcantly and the mean size of pores of both cheeks showed no diference over the course of the study.Sebum secretion did not show any diference over time, but the porphyrin level of both cheeks signifcantly decreased.p value is corrected by Bonferroni correction. *