Search Results (173)

Poly(l-lactic acid) or poly(l-lactide) (PLLA) is an optically active polymer derived from renewable sources and fully biodegradable. It is known that PLLA assumes a left-handed helix in the solid state and also in solution it still keeps a certain degree of helical structure. Here, we examine the Optical Rotatory Dispersion (ORD) behavior of two grades of PLLA (medium molecular weight and hexadecyl-terminated or high molecular weight for 3D printing) in 13 different solvents and analyze the experimental ORD data through the Moffitt–Yang equation. Furthermore, the ORD data of PLLA in additional 6 solvents were taken from the literature and analyzed with the Moffitt-Yang approach. The results suggest that, also in solution, PLLA maintains the left-handed helix, and the most structurizing and helicogenic solvents for PLLA are ethyl acetate, acetonitrile, and certain chlorinated solvents. The equilibrium association constant (K) and other thermodynamic parameters (ΔG°, ΔH° and ΔS°) between PLLA and polyphenylacetylene (PPA, another helical polymer in the solid state and in solution) were determined in trichloromethane, dichloromethane, and tetrahydrofuran. The K values found suggest a strong helix-helix interaction between the two polymers. The ORD analysis of the PLLA-PPA solutions shows evidence of the extrinsic Cotton effect and confirms the chiral helicity induction between the two polymers with 1:1 complex formation. Full article

Background: With the increasing demand for non-surgical facial rejuvenation, injectable collagen biostimulators such as poly-L-lactic acid (PLLA), calcium hydroxyapatite (CaHA), polycaprolactone (PCL), poly-D,L-lactic acid (PDLLA) and powdered polydioxanone (PPDO) have become widely used by facial aesthetic practitioners. These agents stimulate neocollagenesis, providing gradual improvement in skin firmness, elasticity and facial contour with long-lasting results. While manufacturers emphasize the efficacy and favorable safety profile of these products, adverse events such as nodules, edema, inflammatory reactions and, in rare cases, granulomas have been reported. To date, no comprehensive systematic review has evaluated the proportion and nature of adverse effects associated with all major collagen biostimulators in facial aesthetic procedures. This study aims to synthesize current evidence on the proportion of adverse events linked to injectable collagen biostimulators. Methods: The systematic review will include clinical studies involving adults undergoing facial aesthetic procedures with PLLA, PDLLA, CaHA, PCL and PPDO that report adverse events during or after treatment. The search will be conducted in six main databases: CENTRAL, EMBASE, LILACS, PubMed, SCOPUS and Web of Science. No restrictions will be applied regarding language or publication date. The screening process will occur in two phases: first, two independent reviewers will assess titles and abstracts against the eligibility criteria; second, the same reviewers will conduct full-text evaluations. Data will be synthesized narratively, with a meta-analysis of proportions performed if appropriate. Additionally, sample characteristics, treatment protocols, study design and main findings will be reported. The risk of bias will be assessed independently by two reviewers using appropriate tools, based on the study design, with the support of artificial intelligence. PROSPERO registration number: CRD420251062785. Full article

Forward osmosis (FO) membranes face challenges in balancing high water permeability, low reverse salt flux (RSF), and mechanical durability. Although nanopores in graphene have great theoretical potential, the existing methods make it difficult to independently optimize the nanopores of the graphene layer and the microstructure of the substrate without damaging each other. Here, we propose a defect engineering strategy based on oxygen plasma etching to address this collaborative optimization challenge. Monolayer porous graphene (PG) was integrated with polysulfone (Psf) substrates, followed by oxygen plasma etching to introduce nanopores and oxygen-containing functional groups (e.g., carboxyl, hydroxyl). By controlling the etching time to 10 s, the resulting membrane (S-PG10) exhibited a water flux of 0.24 LMH in 0.5 M NaCl, representing an order-of-magnitude increase compared to the pristine graphene membrane (S-G). Remarkably, S-PG10 maintained a high salt rejection (>96%) and a low J_s/J_w (<0.35 g·L⁻¹). Substrate modification via short-term plasma etching (5 min) further doubled the water flux of S*5-PG10 (0.47 LMH in 0.5 M NaCl) by increasing porosity (81.8%→85.6%) and hydrophilicity. However, prolonged etching (>15 min) degraded mechanical strength and increased RSF due to pore structure disruption. To enhance robustness, Poly(D,L-lactic acid) (PDLLA)-doped substrates (S^#-PG) were engineered, with 0.1 wt.% PDLLA optimizing mechanical properties while maintaining low RSF and high flux. Excessive PDLLA (10 wt.%) induced hydrophobicity and crystalline structures, reducing permeability. The study demonstrates that synergistic optimization of plasma etching duration on the graphene selective layer (5~10 s) and substrates (5 min) as well as PDLLA doping (0.1 wt.%) balances pore architecture, surface chemistry, and substrate integrity, achieving FO membranes with superior water-salt selectivity and mechanical stability. These findings provide critical insights into designing high-performance graphene-based membranes for sustainable desalination and water purification. Full article

Background: Nerve conduits are used to bridge peripheral nerve defects caused by trauma, iatrogenic injury, or oncologic disruption. Three-dimensional (3D) biomimetic scaffolds for peripheral nerve regeneration have advanced significantly in recent years, driven by improvements in printing technology and neuronal seeding techniques. We report on published designer conduits that can recreate the epineurium, a critical yet challenging-to-manufacture feature of nerve tissue. Methods: A medical librarian conducted a literature search for our systematic review on EMBASE, Web of Science, and PUBMED, following PRISMA guidelines, for articles from January 2010 to January 2026 for the systematic review. Descriptive statistical analysis was performed using Microsoft 365 Suite software. The literature review was conducted using keywords and search terms describing the history and development of 3DP nerve guidance conduits published prior to January 2026. Results: Our search yielded 273 titles, of which 8 were included after full-text review; these studies used 3D printing to generate nerve conduits for preclinical models. Manual data extraction identified studies reporting successful epineurial recreation. The included scaffold materials were polycaprolactone, poly(l-lactide-co-ε-caprolactone), poly(lactic-co-glycolic acid), acrylate resin, and gelatin methacryloyl. In animal model studies, various terms were used to describe the epineurium outer sheath. Despite this variability in nomenclature, many of these reports indicated successful sciatic functional index (SFI) recovery, favorable g-ratios, good durability, high cell viability, and significant neurite elongation at the time of sacrifice. Conclusions: 3DP nerve conduits targeting the epineurium are promising approaches for treating peripheral nerve defects. The constructs promote oriented growth and myelination. Future research on incorporating the epineurium into nerve scaffolds may consider encapsulating NGF to promote more efficient nerve regeneration, standardizing the definition of epineurial recreation, designing mechanical and permeability reporting benchmarks, and evaluating cell strategies using comparable functional and histologic endpoints. Full article

Hair aging, a complex physiological process involving progressive hair thinning and loss of luster, is primarily driven by functional decline of hair follicle components and sebaceous glands due to cumulative oxidative stress. This decline manifests as dermal papilla cell (DPC) senescence, with reduced insulin-like growth factor-1 (IGF-1) secretion, impaired hair matrix keratinocyte proliferation, and decreased keratin synthesis. We investigated the restorative potential of poly-D,L-lactic acid (PDLLA) filler, a biostimulatory polymer with antioxidant properties, against these age-related changes. PDLLA filler treatment significantly reduced oxidative stress—as indicated by decreased 8-hydroxy-2′-deoxyguanosine (8-OHdG) levels—in hydrogen peroxide-induced senescent human DPCs, alleviated cell-cycle arrest, and significantly upregulated IGF-1 secretion. Conditioned medium from PDLLA filler-treated DPCs stimulated proliferation and pan-keratin expression in senescent hair follicular keratinocytes (HFKs). Intradermal PDLLA filler injection in aged mice significantly reduced 8-OHdG levels, restored DPC proliferative capacity (indicated by proliferating cell nuclear antigen [PCNA] positivity), increased IGF-1 expression within the dermal papilla, and enhanced HFK proliferation in the hair matrix. Consequently, PDLLA filler treatment robustly upregulated hair cortex keratins (K35, K85) and inner root sheath markers (AE15, K25, K71), leading to improved cuticle integrity and the attenuation of follicular miniaturization. Senescence within sebaceous glands was also mitigated, as evidenced by increased PCNA and peroxisome proliferator-activated receptor gamma (PPAR-γ) expression, accompanied by enhanced hair shaft reflectivity and shine. Overall, PDLLA filler ameliorated senescence-associated phenotypes and restored senescence-associated functional decline, supporting its potential as an intervention for age-related hair thinning and quality deterioration. Full article

To construct a high-performance avermectin (Avm) carrier system, this study utilized the advantages of stereocomplex (SC) crystal formation between poly (L-lactic acid) (PLLA) and poly (D-lactic acid) (PDLA) to prepare Avm-loaded stereocomplex polylactic acid (SC-PLA) nanoformulations via the emulsion solvent evaporation method. The results showed the successful formation of SC-PLA after introducing PDLA into the PLLA matrix, and the influence of SC-PLA crystallinity enabled the fabrication of tunable Avm@SC-PLA nanospheres with a regular spherical morphology. Avm@SC-PLA exhibited controlled release characteristics and possessed pH-responsive properties with specific release behaviors under pH 5.5, 7.4, and 8.0 conditions. The Avm@SC-PLA sustained-release nano system had a series of advantages, including controllable particle size, efficient drug loading, excellent sustained-release performance, good UV-shielding ability, high stability, favorable spreadability, and strong affinity for different leaves. In conclusion, the Avm@SC-PLA nanoformulation not only achieves effective loading and stable encapsulation of Avm but also possesses good structural stability and environmental responsiveness. It provides a novel PLA-based carrier strategy for the efficient delivery of Avm and holds potential application value in the pesticide and pharmaceutical fields. Full article

Introduction: Polylactic acid can be classified into poly(L-lactic acid) (PLLA) and poly(D,L-lactic acid) (PDLLA) according to their stereoisomeric structures, and both are widely used as dermal fillers for soft tissue augmentation. Although the clinical efficacy of commercially available PLLA- and PDLLA-based fillers has been well established, variations in their physicochemical properties may lead to differences in handling characteristics and clinical performance. A systematic comparison of these properties among different PLA-based fillers remains limited. Materials and Methods: In this study, the physicochemical characteristics of three PDLLA-based fillers (AestheFill, NeoFilera, and Juvelook) and one PLLA-based filler (Sculptra) were evaluated. The analyses included functional group identification, particle morphology and size distribution observation, reconstitution time measurement, osmotic pressure determination, and viscosity assessment. Results: AestheFill and NeoFilera exhibited similar profiles in terms of functional groups, size distribution, osmotic pressure, and viscosity, while NeoFilera and Juvelook showed comparable particle morphologies. Sculptra displayed distinct particle morphology and viscosity, likely attributable to its PLLA composition, yet showed similarities with Juvelook in functional group identification and osmotic pressure. Additionally, the reconstitution times of Sculptra, NeoFilera, and Juvelook were significantly shorter than that of AestheFill. Conclusions: Although the direct correlation between physicochemical characteristics and clinical outcomes warrants further investigation, this comparative analysis provides clinicians with a clearer understanding of the material properties of PLA-based dermal fillers and may assist in the informed selection of appropriate products for individual patients. Full article

Introduction: In this study, we aimed to optimize the microfluidizer-based preparation of poly(lactic-co-glycolic acid) nano-micelles (PLGANM), increasingly used for parenteral delivery of poorly water-soluble drugs but typically exhibiting poor physical stability when produced by conventional methods. Method: By systematically tuning microfluidization (MFZ) parameters, we demonstrate an efficient strategy to enhance PLGANM stability and ensure robust, scalable manufacturing, relevant for long-term storage and clinical translation applications. The influence of several key factors designed by Central Composite Design (CCD), including the amount of PLGA and Tween 80, homogenization pressure, and number of passes of MFZ on the size, polydispersity (measured by DLS), and hence stability of the PLGANM, was analyzed for 60 days. 60 PLGANMs produced by the MFZ method (PMFZ) were compared with the PLGANM consisting of equivalent amounts of PLGA and T80 produced using the traditional oil-in-water method (POW). Desired limits were set to minimize standard deviations for Z-average, Zeta Potential, and PDI. Results: Coded variables for optimized PMFZ (OPMFZ) were found to be 82.96 mg PLGA, 6.78 mL 5% T80, 11,000 psi pressure, and 1 pass. Conclusions: This study demonstrates that microfluidization, when guided by a QbD framework, offers precise control over particle attributes and enables reproducible production of stable PLGANM. Full article

Age-associated hair loss is primarily driven by decreased function and proliferation of hair follicle stem cells (HFSCs), often exacerbated by increased inhibitory signaling and changes in the stem cell niche. Macrophage polarization to the anti-inflammatory M2 phenotype is known to increase stem cell proliferation. We investigated the effects of poly-D,L-lactic acid (PDLLA) on hair growth in middle-aged skin, focusing on its role in modulating macrophage polarization and HFSC activity. Senescent macrophages were analyzed for Piezo1 activity, macrophage polarization, and secretion of hepatocyte growth factor (HGF) and insulin-like growth factor-1 (IGF-1) after PDLLA treatment. Downstream effects on HFSC proliferation, stemness, and Wnt signaling were assessed, including inhibition experiments using the Piezo1 blocker GsMTx4. In vivo analyses assessed hair follicle number, diameter, length, anagen duration, and hair coverage following PDLLA administration in middle-aged mice. PDLLA increased Piezo1 expression and activity in senescent macrophages, enhancing M2 polarization and secretion of HGF and IGF-1. This activated the RAS/ERK signaling pathway, promoting HFSC proliferation and stemness. Furthermore, PDLLA upregulated Wnt signaling molecules (Wnt3a, Wnt10b, and β-catenin) and anagen phase-related factor (Axin2, LEF1, and Lgr5), which were decreased by GsMTX4. In middle-aged animal skin, PDLLA administration led to increased hair follicle number, diameter, and length, as well as prolonged anagen and greater hair coverage. Collectively, these findings suggest that PDLLA rejuvenates the middle-aged skin microenvironment, at least in part through Piezo1-associated M2 macrophage polarization and enhanced HFSC function, offering a promising therapeutic strategy for age-related hair loss targeting both the immune and the stem cell compartments. Full article

Fused filament fabrication (FFF) is a widely used material extrusion-based 3D printing process known for its cost-effectiveness, versatility, and ability to produce intricate components. However, the strength of interlayer bonding is significantly influenced by printing parameters, material characteristics, and the chosen printing paths. The present study employs a custom response surface design derived from an L9 orthogonal array to strictly investigate the impact of three distinct infill patterns under varying printing temperatures and printing speeds on the responses of flexural strength, σ_b, and elasticity modulus, E (MPa). Flat-oriented poly-lactic acid (PLA) specimens were subjected to three-point bending tests to evaluate flexural strength for 100% infill rates and a 0.2 mm layer height. Besides the experimental investigation and the statistical analysis, failure modes of the fractured samples were observed to correlate the independent printing parameters with the aforementioned response. The desirability function was employed to identify the set of optimal parameters for maximizing the flexural strength and elasticity modulus for the particular PLA material brand examined. The results indicated that infill pattern and printing speed have significant impact on both responses. The optimal parameters were identified as “centroid” for infill style, 203.03 °C for printing temperature and 25 mm/s for printing speed. Full article

Tendon injuries present significant clinical challenges due to limited intrinsic healing and complex pathological mechanisms. Here, we developed a novel 3D bioprinted methacrylated type I collagen (ColMA) scaffold integrated with Growth Differentiation Factor-5 (GDF-5)-loaded Poly (lactic-co-glycolic acid) (PLGA) nanoparticles and dynamically cultured it under perfusion to establish a tenogenic microenvironment in vitro. Pathological human Tendon Stem/Progenitor Cells (hTSPCs) derived from tendinopathic surgical explants were encapsulated to investigate their impaired extracellular matrix (ECM) deposition and associated pro-inflammatory signaling. GDF-5-loaded nanoparticles (average diameter 140 ± 40 nm) were fabricated via microfluidic-assisted nanoprecipitation and homogeneously incorporated within the ColMA synthetic ECM to enable sustained growth factor release. Continuous perfusion culture (1 mL/min) ensured efficient mass transfer and supported cell viability above 70% over 21 days. Pathological hTSPCs exhibited impaired ECM remodeling, characterized by the absence of type I collagen and a 2.56-fold increase in type III collagen at day 7, indicative of a fibrotic-like phenotype. Western blot densitometry demonstrated a 5.31-fold elevation in secreted tenomodulin at day 14, while ECM analysis verified a type III to type I collagen ratio of 4.5. In addition, a markedly pro-inflammatory cytokine profile was observed, with elevated secretion of interleukin-6 (IL-6) and interleukin-8 (IL-8) from day 7 onward, consistent with the chronic inflammatory status of cells derived from pathological tendon tissues. This modular 3D platform represents a robust in vitro model for mechanistic studies and the advancement of personalized regenerative strategies targeting chronic tendon disorders. Full article

This study aimed to engineer nanofibrous scaffolds that prioritize architecture, rather than relying solely on the drug, to achieve reproducible, long-acting local therapies. Cotton-wool-like fiber, three-dimensional (3D) poly(L-lactic acid)/polyethene glycol (PLLA/PEG) blend scaffolds were fabricated using solution blow spinning (SBS) as a customizable encapsulation platform for controlled antibiotic release. Morphological and wettability analyses were performed by scanning electron microscopy (SEM) and pendant-drop contact angle measurements, respectively. Fiber diameters were quantified using ImageJ. The chemical composition and thermal behavior were investigated by Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). In vitro, assays were conducted to assess the antimicrobial activity of vancomycin-loaded scaffolds against Staphylococcus aureus (disk diffusion method), as well as their cytocompatibility (Live/Dead assay in Vero cells) and hemocompatibility (ASTM F756-17 hemolysis test). All biological data were statistically analyzed using ANOVA with Tukey’s post-test, Mann–Whitney, and paired t-tests, with significance set at p ≤ 0.05. Structural optimization identified PLLA/PEG 85:15 as the most stable composition, producing homogeneous mats with high porosity and rapid wettability. Incorporation of vancomycin (10 wt.%) reduced the fiber diameter (0.23 ± 0.11 µm) compared with unloaded scaffolds (0.32 ± 0.17 µm), indicating drug–polymer interactions that modulated jet elongation. FTIR, DSC, and TGA analyses confirmed polymer miscibility and stabilization of VMC within the fibrous matrix, with no signs of degradation. Drug release exhibited a biphasic profile, with an initial burst during the first 72 h. PLLA/PEG–VMC scaffolds produced larger inhibition zones against S. aureus (18.55 mm ± 1.2 to 6.63 mm ± 0.2 at 120 h) compared with free VMC (12.91 mm ± 3.8 to 4.07 mm ± 0.6291), while blank scaffolds were inactive. Hemolysis remained within the range 2% < PLLA/PEG–VMC < 5%, indicating acceptable hemocompatibility according to ASTM standards. Although VCM-loaded PLLA/PEG scaffolds slightly reduced Vero cell viability, no statistically significant differences were observed compared with the control group. These findings demonstrate that the architecture of nanofibers presents itself as a potential platform for antimicrobial therapy with topical vancomycin in potential applications such as wound dressings or implant coatings. Full article

This study evaluates the tribological properties of poly-DL-lactic acid (PDLLA) nanosheets attached to shark-skin surfaces with varying textures. The main goal was to assess friction reduction in samples with different surface textures and investigate the influence of PDLLA nanosheets on tribological behaviors. Biomimetic shark skin was created using a polydimethylsiloxane (PDMS)-embedded stamping method (PEES) that replicates shark skin’s unique texture, which reduces friction and drag in aquatic environments. PDLLA nanosheets, with a controlled thickness of several tens of nanometers, were fabricated and attached to the PDMS surfaces. The morphological characteristics of the materials were analyzed before and after attaching the PDLLA nanosheets using scanning electron microscopy (SEM), revealing the uniformity and adherence of the nanosheets to the PDMS surfaces. Friction tests were conducted using force transducers to measure the friction coefficients of biomimetic shark skin, biological models, and flat PDMS and silicon substrates, allowing a comprehensive comparison of frictional properties. Additionally, sliding tests with human fingers were performed to assess friction coefficients between various fingerprint shapes and sample surfaces. This aspect of the study is critical for understanding how human skin interacts with biomimetic materials in real-world applications, such as wearable devices. These findings clarify the relationship between surface texture, nanosheets, and their tribological performance against human skin, thereby contributing to the development of materials with enhanced friction-reducing properties for applications such as surface coatings, substrates for wearable devices, and wound dressings. Full article

This study focuses on the synthesis and characterization of thermoresponsive hydrogels of poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG), PLA–PEG copolymers, aiming at the targeted and controlled release of deferoxamine (DFO), a clinically applied iron-chelating drug. Triblock (PLA-PEG-PLA) and diblock (mPEG-PLA) copolymers were synthesized using ring-opening polymerization (ROP) with five different PEGs with molecular weights of 1000, 1500, 2000, 4000, and 6000 g/mol and two types of lactide (L-lactide and D-lactide). Emulsions of the polymers in phosphate-buffered saline (PBS) were prepared at concentrations ranging from 10% to 50% w/w to study the sol–gel transition properties of the copolymers. Amongst the synthesized copolymers, only those that demonstrated thermoresponsive sol-to-gel transitions near physiological temperature (37 °C) were selected for further analysis. Structural and molecular confirmation was performed by Nuclear Magnetic Resonance (NMR) and Fourier-transform infrared spectroscopy (FTIR), while the molecular weights were determined via Gel Permeation Chromatography (GPC). The thermal transitions were studied by calorimetry (DSC) and crystallinity via X-ray diffraction (XRD) analysis. DFO-loaded hydrogels were prepared, and their drug release profiles were investigated under simulated physiological conditions (37 °C) for seven days using HPLC analysis. The thermoresponsive characteristics of these systems can offer a promising strategy for injectable drug delivery applications, where micelles serve as drug carriers and undergo in situ gelation, enabling controlled release. This alternative procedure may significantly improve the bioavailability of DFO and enhance patient compliance by addressing key limitations of conventional administration routes. Full article

Poly(L-lactic acid) (PLLA) and iron (Fe) are popular bioresorbable material candidates for biomedical implants. However, PLLA coronary stents are relatively too thick compared to metallic stents when providing the same mechanical strength, while iron degrades too slowly. Recent studies show that PLLA coatings can enhance iron’s corrosion rate, and iron has strong mechanical strength, making PLLA–Fe composites ideal for bioresorbable implants. Although PLLA coatings on iron samples have been studied, research on embedding iron wires in relatively thick PLLA matrices is limited. Moreover, no studies have yet explored 3D-printed metal wire-reinforced PLLA monofilaments for biomedical applications. To address these research gaps and investigate the in vitro degradation profile of PLLA/Fe wire monofilaments for bioresorbable stents, this study first developed a novel polymer filament–metal wire coextrusion 3D printer for printing PLLA/Fe wire monofilaments. In vitro degradation tests were then conducted on both PLLA/Fe and neat PLLA monofilaments at 50 °C. Thereafter, characterizations, including mass loss, pH, surface appearance and morphology, tensile tests, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC), were performed. Results indicated that the overall degradation rate of PLLA/Fe monofilaments was higher than that of PLLA counterparts, while the degradation rate of PLLA matrix was not affected by the embedded iron wire according to molecular weight analysis. Notably, the Young’s modulus and stiffness of PLLA monofilaments were significantly improved by the iron wires during the early stages of degradation, but the reinforcement in tensile strength was negative after immersion due to the poor embedding quality of the iron wires in the PLLA monofilaments. With future improvement of the embedding quality of iron wire, the 3D-printed PLLA/Fe wire composites can have great potential in the development of biomedical devices using the novel 3D printing method, including most types of stents and bone scaffolds. Full article