Background/Objectives: Acne vulgaris is a chronic skin infection characterized by high sebum secretion, keratosis around hair follicles, inflammation, and imbalance in androgen levels. Acne vulgaris causes permanent scars or skin pigmentation in cases of improper treatment. Oral or topical isotretinoin, contraceptives, and antibiotics are used to treat acne. Minocycline is one of the widely used tetracyclines for this purpose; it inhibits the synthesis of proteins in bacterial ribosomes. Commonly, minocycline is prescribed daily for several months for acne vulgaris. Systemic minocycline is highly distributed into body fluids, and it is associated with several side effects and antibiotic resistance. Additionally, minocycline is highly metabolized in the liver, leading to reduced bioavailability upon systemic delivery. This study aims to develop and characterize minocycline nanocrystals for targeted skin delivery and evaluate their antimicrobial efficacy in treating acne vulgaris. Methods: Minocycline nanocrystals were synthesized using milling or solvent evaporation techniques. Nanocrystals were characterized in terms of particle size, particle distribution index (PDI), zeta potential, and morphology. The antibacterial efficacy against Propionibacterium acne, Staphylococcus aureus, and Staphylococcus epidermidis was evaluated using a minimum inhibitory concentration assay (MIC) and agar well diffusion test in comparison to coarse minocycline. Results: Minocycline nanocrystals had a particle size of 147.4 ± 7.8 nm and 0.27 ± 0.017 of PDI. The nanocrystals exhibited a loading efficiency of 86.19 ± 16.7%. Antimicrobial testing showed no significant difference in activity between minocycline and its nanoparticle formulation. In terms of skin deposition, the nanocrystals were able to deliver minocycline topically to rat skin significantly more than free minocycline. The nanocrystal solution deposited 554.56 ± 24.13 μg of minocycline into rat skin, whereas free minocycline solution deposited 373.99 ± 23.32 μg. Conclusions: Minocycline nanocrystals represent a promising strategy for targeted skin delivery in the treatment of acne vulgaris, potentially reducing systemic side effects and antibiotic resistance and improving patient outcomes.

Acne is a multifactorial skin condition characterized by an infection in the pilosebaceous units in the skin. Patients with acne suffer from comedones, papules, pustules and nodules or cysts in severe cases. These clinical features might cause disfigurmentation, depression, anxiety and significantly impact the quality of life of patients. Systemic and continuous exposure of antibiotics put patients at risk of developing systemic toxicity, bacterial resistance and gut dysbiosis. Microneedles offer an innovative approach of providing targeted topical delivery of minocycline while insuring efficient permeation through skin layers. Methods: minocycline microneedles were formulated using casting method and characterized for insertion ability, mechanical strength, drug content, antibacterial activities, deposition and dissolution behavior using ex vivo full-thickness rat skin. Results: Insertion tests confirmed effective skin penetration and mechanical integrity with only 9.5% height reduction. Drug content was 673.06 ± 5.34 µg/array. Dissolution occurred within 2 min in skin, indicating user-friendly wear time. Ex vivo Franz diffusion studies showed 26% of the drug deposited into the skin, significantly higher (p = 0.0068) than the 18.3% that permeated through it. Antibacterial testing revealed strong activity against S. aureus, S. epidermidis, and C. acnes, with MIC values < 0.146 µg/mL and MBC values ranging from 9.375–18.75 µg/mL. Conclusions: The result of this research demonstrate that minocycline microneedles effectively deliver minocycline into the skin highlighting their potential as a safer and more efficient alternative for acne therapy.

Acne is a multifactorial skin condition characterized by an infection in the pilosebaceous units in the skin. Patients with acne suffer from comedones, papules, pustules and nodules or cysts in severe cases. These clinical features might cause disfigurmentation, depression, anxiety and significantly impact the quality of life of patients. Systemic and continuous exposure of antibiotics put patients at risk of developing systemic toxicity, bacterial resistance and gut dysbiosis. Microneedles offer an innovative approach of providing targeted topical delivery of minocycline while insuring efficient permeation through skin layers. Methods: minocycline microneedles were formulated using casting method and characterized for insertion ability, mechanical strength, drug content, antibacterial activities, deposition and dissolution behavior using ex vivo full-thickness rat skin. Results: Insertion tests confirmed effective skin penetration and mechanical integrity with only 9.5% height reduction. Drug content was 673.06 ± 5.34 µg/array. Dissolution occurred within 2 minutes in skin, indicating user-friendly wear time. Ex vivo Franz diffusion studies showed 26% of the drug deposited into the skin, significantly higher (p = 0.0068) than the 18.3% that permeated through it. Antibacterial testing revealed strong activity against S. aureus, S. epidermidis, and C. acnes, with MIC values <0.146 µg/mL and MBC values ranging from 9.375–18.75 µg/mL. Conclusion: The result of this research demonstrate that minocycline microneedles effectively deliver minocycline into the skin highlighting their potential as a safer and more efficient alternative for acne therapy.