Water absorbing and quick degradable PLLA/PEG multiblock copolymers reduce the encapsulation and inflammatory cytokine production

Cross-linked Sodium Hyaluronate Gel with PLLA-b-PEG Microsphere for Facial Contouring in Chinese: A Retrospective Study

BACKGROUND

In Asia, the demand for cosmetic facial treatments has surged due to technological advancements, increased social acceptability, and affordability. Poly-L-lactic acid (PLLA) fillers, known for their biocompatibility and biodegradability, have emerged as a popular choice for facial contouring, yet studies specifically addressing their use in Asian populations are scarce.

METHODS

This retrospective study examined 30 Chinese patients who underwent facial contouring with PLLA fillers, focusing on product composition, injection techniques, and safety measures. A comprehensive clinical evaluation was performed, including the Global Aesthetic Improvement Scale (GAIS) and Global Impression of Change Scale (GICS) for effectiveness and patient satisfaction, respectively.

RESULTS

No significant difference in GAIS scores was observed between injectors and blinded evaluators over a 12-month period, indicating consistent effectiveness. Patient satisfaction remained high, with GICS scores reflecting positive outcomes. The safety profile was favorable, with no serious adverse events reported. The study highlighted the importance of anatomical knowledge to avoid complications, particularly in areas prone to blindness.

CONCLUSIONS

PLLA fillers offer a safe, effective option for facial contour correction in the Asian population, achieving high patient satisfaction and maintaining results over time. The study underscores the need for tailored approaches in cosmetic procedures for Asians, considering their unique facial structures and aesthetic goals. Further research with larger, multicenter cohorts is recommended to validate these findings and explore long-term effects.

LEVEL OF EVIDENCE III

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Initial immune response to a FRET-based MMP sensor-immobilized silk fibroin hydrogel in vivo

To investigate the initial immune response to biodegradable silk fibroin (SF) hydrogels in vivo, a Förster/fluorescence resonance energy transfer (FRET)-based sensor was developed to detect matrix metalloproteinase (MMP) activity (FRET-MMPS) and immobilized to SF hydrogel. FRET-MMPS immobilized to SF hydrogel in vitro displayed intra-molecular FRET more than inter-molecular FRET, and MMP activity was detected through a decrease in FRET signal intensity. Then, the SF hydrogel modified with FRET-MMPS was implanted into mice subcutaneously, and it was observed that the FRET signal intensity decreased significantly soon (< 3 h) after implantation. Although the intensity exhibited a sharp decrease toward 24 h post-implantation, histological evaluation proved that bulk-level hydrogel degradation, such as breakdown, was mainly caused by macrophages and foreign body giant cells on a timescale of weeks. These results indicated that, immediately upon implantation, active MMPs reached the SF hydrogel and began cleaving SF networks, which might result in the loosening of the networks and then enabled immune cells, such as macrophages, to start the bulk-level hydrogel degradation. The sensor clarified the initial immune response to SF hydrogels and will provide clues for designing the biodegradation behaviors of scaffolds for regenerative medicine. STATEMENT OF SIGNIFICANCE: Silk fibroin (SF) materials are degraded gradually by the immune response. Immune cells, such as macrophages, break down implanted SF materials on a timescale of weeks or months, but the initial (< 24 h) immune response to SF materials remains unclear. In this study, SF hydrogels modified with Förster/fluorescence resonance energy transfer (FRET)-based matrix metalloproteinase (MMP) sensors were implanted in mice and within 3 h post-implantation, the SF hydrogels were degraded by MMPs. Although this molecular-level biodegradation was not correlated with the hydrogel breakdown, the MMPs were likely to loosen the SF networks to enable immune cells to infiltrate and degrade the hydrogel. This is the first study to unveil the initial stage of immune response to biomaterials.

Effect of Thermoresponsive Poly(L-lactic acid)-poly(ethylene glycol) Gel Injection on Left Ventricular Remodeling in a Rat Myocardial Infarction Model

Some gel types have been reported to prevent left ventricular (LV) remodeling in myocardial infarction (MI) animal models. In this study, we tested biodegradable thermoresponsive gels. Poly(L-lactic acid)-poly(ethylene glycol) (PLLA-PEG) and poly(D-lactic acid)-poly(ethylene glycol) (PDLA-PEG) were synthesized by the polycondensation of l- and D-lactic acids in the presence of PEG and succinic acid. Each of these block copolymers was used to prepare particles dispersed in an aqueous medium and mixed together to obtain a PLLA-PEG/PDLA-PEG suspension, which was found to show a sol-to-gel transition around the body temperature by the stereocomplex formation of enantiomeric PLLA and PDLA sequences. In the present study, the G' of the PLLA-PEG/PDLA-PEG suspension in the rheological measurement remained as low as 1 Pa at 20 °C and increased 2 kPa at 37 °C. The sol-gel systems of PLLA-PEG/PDLA-PEG might be applicable to gel therapy. The effect of the PLLA-PEG/PDLA-PEG gel injection was compared with that of a calcium-crosslinked alginate gel and saline in a rat MI model. The percent fractional shortening improved in the PLLA-PEG/PDLA-PEG (20.8 ± 4.1%) and alginate gel (21.1 ± 4.8%) compared with the saline (14.2 ± 2.8%) with regard to the echocardiograph 4 weeks after the injection (p < 0.05). There were reduced infarct sizes in both PLLA-PEG/PDLA-PEG gel and alginate gel compared with the saline injection (p < 0.05). Moreover, a greater reduction in LV cavity area was observed with the PLLA-PEG/PDLA-PEG gel than with the alginate gel (p = 0.06). These results suggest that the PLLA-PEG/PDLA-PEG gel should have high therapeutic potential in gel therapy for LV remodeling after MI.

Degradation, intra-articular retention and biocompatibility of monospheres composed of [PDLLA-PEG-PDLLA]-b-PLLA multi-block copolymers

In this study, we investigated the use of microspheres with a narrow particle size distribution ('monospheres') composed of biodegradable poly(DL-lactide)-PEG-poly(DL-lactide)-b-poly(L-lactide) multiblock copolymers that are potentially suitable for local sustained drug release in articular joints. Monospheres with sizes of 5, 15 and 30μm and a narrow particle size distribution were prepared by a micro-sieve membrane emulsification process. During in vitro degradation, less crystallinity, higher swelling and accelerated mass loss during was observed with increasing the PEG content of the polymer. The monospheres were tested in both a small (mice/rat) and large animal model (horse). In vivo imaging after injection with fluorescent dye loaded microspheres in mice knees showed that monospheres of all sizes retained within the joint for at least 90days, while the same dose of free dye redistributed to the whole body within the first day after intra-articular injection. Administration of monospheres in equine carpal joints caused a mild transient inflammatory response without any clinical signs and without degradation of the cartilage, as evidenced by the absence of degradation products of sulfated glycosaminoglycans or collagen type 2 in the synovial fluid. The excellent intra-articular biocompatibility was confirmed in rat knees, where μCT-imaging and histology showed neither changes in cartilage quality nor quantity. Given the good intra-articular retention and the excellent biocompatibility, these novel poly(DL-lactide)-PEG-poly(DL-lactide)-b-poly(L-lactide)-based monospheres can be considered a suitable platform for intra-articular drug delivery.

STATEMENT OF SIGNIFICANCE

This paper demonstrates the great potential in intra-articular drug delivery of monodisperse biodegradable microspheres which were prepared using a new class of biodegradable multi-block copolymers and a unique membrane emulsification process allowing the preparation of microspheres with a narrow particle size distribution (monospheres) leading to multiple advantages like better injectability, enhanced reproducibility and predictability of the in vivo release kinetics. We report not only on the synthesis and preparation, but also in vitro characterization, followed by in vivo testing of intra-articular biocompatibility of the monospheres in both a small and a large animal model. The favourable intra-articular biocompatibility combined with the prolonged intra-articular retention (>90days) makes these monospheres an interesting drug delivery platform. What should also be highlighted is the use of horses; a very accurate translational model for the human situation, making the results not only relevant for equine healthcare, but also for the development of novel human OA therapies.

Macrophage reaction against biomaterials in the mouse model - Phenotypes, functions and markers

The foreign body reaction (FBR) is a response of the host tissue against more or less degradation-resistant foreign macromolecular material. The reaction is divided into five different phases which involve most aspects of the innate and the adaptive immune system: protein adsorption, acute and chronic inflammation, foreign body giant cell formation and fibrosis. It is long known, that macrophages play a central role in all of these phases except for protein adsorption. Initially it was believed that the macrophage driven FBR has a complete negative effect on biocompatibility. Recent progress in biomaterial and macrophage research however describe macrophages as more than pure antigen phagocytosing and presenting cells and thus pro-inflammatory cells involved in biomaterial encapsulation and failure. Quite contrary, both, pro-inflammatory M1 macrophages, the diverse regulatory M2 macrophage subtypes and even foreign body giant cells (FBGC) are after necessary for integration of non-degradable biomaterials and degradation and replacement of degradable biomaterials. This review gives a comprehensive overview on the taxonomy of the currently known macrophage subtypes. Their diverging functions, metabolism and markers are summarized and the relevance of this more diverse macrophage picture for the design of biomaterials is shortly discussed.

STATEMENT OF SIGNIFICANCE

The view on role of macrophages in the foreign body reaction against biomaterials is rapidly changing. Despite the initial idea that macrophage are mainly involved in undesired degradation and biomaterial rejection it becomes now clear that they are nevertheless necessary for proper integration of non-degradable biomaterials and degradation of placeholder, degradable biomaterials. As a pathologist I experienced a lack on a good summary on the current taxonomy, functions and phenotypes of macrophages in my recent projects on the biocompatibility of biomaterials in the mouse model. The submitted review therefore intends to gives a comprehensive overview on the taxonomy of the currently known macrophage subtypes. Their diverging functions, metabolism and markers are summarized and the relevance of this more diverse macrophage picture for the design of biomaterials is shortly discussed.