KR-1-2

Bacterial infections remain a leading cause of failure in biomedical implants. To mitigate this, surface modification strategies have been developed, commonly relying on bactericidal agents such as antibiotics to eliminate attached bacteria. However, the rise of antibiotic resistance has significantly reduced the long-term success of these approaches. Antimicrobial peptides (AMPs), such as KR-12, have emerged as promising alternatives due to their strong bactericidal activity and low risk of inducing resistance. This study presents a surface engineering strategy that combines the antimicrobial action of KR-12 with the antifouling properties of polyethylene glycol (PEG) linkers. Low-pressure plasma treatment was used to generate primary amine groups on titanium surfaces. These amine groups not only enable sequential covalent attachment of PEG and AMPs but also enhance surface energy and wettability, which promote favourable protein adsorption and cell behaviour without altering surface topography. Plasma parameters were optimised to maximise amine group formation, achieving up to 9.18 % nitrogen atoms associated with primary amines, confirmed by X-ray photoelectron spectroscopy (XPS). Functionalisation was verified using atomic force microscopy (AFM), water contact angle (WCA) measurements, and Fourier Transform Infrared Spectroscopy (FTIR). Antimicrobial testing against four pathogenic strains showed over 90 % inhibition of bacterial adhesion and biofilm formation, attributed to the combined effects of KR-12 and PEG. Moreover, cell viability assays and scanning electron microscopy (SEM) confirmed excellent biocompatibility and cell adhesion. Using a simple N₂/H₂ gas mixture, this plasma-based method enables efficient surface functionalisation with reduced chemical usage and processing time. This work introduces a promising strategy for engineering implant surfaces that are both infection-resistant and supportive of tissue integration.

Cathelicidin LL-37, an antimicrobial peptide (AMP) of the innate immune system, wards off bacterial infections. Recent research has identified plenty of biological functions of AMPs beyond their antimicrobial activity, including antioxidant, self-renewal, and procollagen properties, making them valuable for antiaging products. In this study, we assessed the antiphotoaging potential of cathelicidin LL-37 fragments and KR-12 analogs using human immortalized keratinocytes (HaCaT) and human dermal fibroblasts (HDF). Our results reveal that these peptides can modulate ultraviolet-radiation-induced photodamage, exhibiting anti-inflammatory and antioxidant properties. Notably, we proved the immune modulation effects of LL-23. Additionally, these peptides promote cell migration and collagen synthesis, inhibit glycation, and suppress melanin production. We propose that the antiphotoaging effects exhibited by LL-37 fragments and KR-12 analogs are related to the alleviation of inflammation, and we attempt to elucidate the possible underlying mechanisms. These findings support their efficacy as antiaging agents in dermatological applications.