Hyaluronic Acid Solution Research Articles

Biocompatible hyaluronic acid-divinyl sulfone injectable hydrogels for sustained drug release with enhanced antibacterial properties against Staphylococcus aureus

Hyaluronic acid (HA) solutions were crosslinked with divinyl sulfone (DVS) and subsequently loaded with antibiotic molecules to obtain biocompatible and antibacterial injectable hydrogels. The crosslinking degree of the hydrogels was modulated by varying the reaction time and the HA:DVS weight ratio. Synthesized HA-DVS hydrogels were characterized by their rheological properties, pore size, swelling capacity and hydrolytic and thermal degradation. Biocompatibility was assessed by measuring pH, osmolality and by in vitro cytotoxic assay. Acetyl salicylic (AAS) loaded hydrogels display anti-inflammatory properties in vitro, whereas cefuroxime (CFX), tetracycline (TCN) and amoxicillin (AMX) loaded hydrogels show in vitro antibacterial activity against Staphylococcus aureus. The combine use of antibiotics and AAS produces a synergic effect that reduces the S. aureus population up to a log10 reduction (R) of 5.55. Overall results show that antibiotic/AAS loaded HA-DVS hydrogels could be effectively used to combat S. aureus infections and to increase the antibacterial activity of antibiotics commonly used against S. aureus.

<i>In vitro</i> induction of regenerative and osteogenic activity of PDLSC cells

The restoration of damaged tissues in periodontal diseases is not only a medical problem, but also a social one. Periodontal diseases often entail the loss of a large number of teeth (more than with any other disease of the dentition), as a result, a violation of the act of chewing and speech, a negative effect on the general condition of the body and, as a result, a decrease in the quality of human life. Purpose of the study: to study the regenerative activity of a lyophilized extract of a chicken embryo of various concentrations in the composition of hyaluronic acid in relation to the culture of PDLSC cells in an in vitro experiment. Comparison groups: A solution of 1% unmodified hyaluronic acid containing lyophilized chicken embryo extract in three concentrations: 300 μg/ml, 150 μg/ml, 75 μg/ml. As a control, 1% solution of unmodified hyaluronic acid. Hyaluronic acid is a natural substance that is an important component of the extracellular matrix as a mineralized and non-mineralized tissue. Its use attracts the attention of specialists as an object capable of acquiring new properties with its various modifications. In our laboratory studies, stem cells from a culture of human periodontal disease were used. Periodontitis stem cells (PDLSC periodontal ligament) were discovered in 2004. Cell adhesion and tissue penetration were investigated by impedimetry. Analysis to assess cell viability was carried out using a solution containing a water-soluble tetrazolium salt. Differentiation of osteogenic direction without induction was measured three weeks after dilution of stem cells in traditional culture medium. Staining was carried out according to the Koss method. To assess mineralization, cells were stained with alizarin red, followed by assessment of calcium deposition in them. It was found that the resulting PDLSC cell population during the experiment was heterogeneous and showed healthy fibroblast morphology in all three study groups. Lyophilized extract of chicken embryo as part of a preparation based on hyaluronic acid does not significantly affect the survival and proliferation of PDLSC cells, however, at high concentrations (150 μg/ml and 300 μg/ml) it induces osteogenic activity of cells, increases mineralization without causing calcium deposition, which indicates regenerative activity. Osteogenic transdifferentiation is an attractive way to create cells of osteogenic cellular origin. The results of our study show that they can be used to model bone diseases.

Lubricant Effects on Articular Cartilage Sliding Biomechanics Under Physiological Fluid Load Support

Articular cartilage maintains phenomenally low friction and strains in intact joints during articulation, yet after a century of study, the mechanisms underpinning cartilage’s in vivo functions remain uncertain. We recently re-introduced a unique benchtop testing system, the convergent stationary contact area (cSCA), to investigate frictions and strains in cartilage explants; the cSCA differs from other benchtop testing configurations by enabling sliding-induced hydrodynamic-driven fluid flows to influence interstitial hydration and lubrication during sliding. This study aimed to elucidate several points regarding cartilage tribomechanics and joint lubrication, including the following: (i) if the presence of putative lubricants alters the ability of sliding to drive tribological rehydration (i.e., sliding-driven compression recovery under loading); (ii) how lubricant presence influences the frictional behavior of articular cartilage when tested under physiologically representative sliding conditions (e.g., moderate-to-high hydration and fluid load support, low-to-moderate tissue strains, and fast sliding speeds); and (iii) interpreting these behaviors with respect to lubricant rheology at shear rates reflecting those found in cSCA tests and intact joints (> 104 s−1). We found that synovial fluid and hyaluronic acid solutions (i) were at most 3–10 × the viscosity of saline lubricants at physiological shear rates, (ii) substantially enhanced the rates of fluid and lubrication recovery during sliding, and (iii) minimized the amount of time the explants experienced detrimental ‘pathophysiological’ frictions by fostering tissue hydration recovery. Additionally, we show that when non-lubricating solutions and high sliding speeds are utilized, the cSCA can facilely replicate ‘semi-physiological’ strains and frictions, while the use of lubricant-containing baths fosters ‘physiologically consistent’ tribomechanical behaviors, improving the physiological relevance of long-term benchtop sliding tests.

Engineered synthetic cell penetrating peptide with intracellular anti-inflammatory bioactivity: An in vitro and in vivo study.

Various biomaterials have been used for bone and cartilage regeneration, and inflammation associated with biomaterial implantation is also increased. A 15-mer synthetic anti-inflammatory peptide (SAP15) was designed from human β-defensin 3 to penetrate cells and induce intracellular downregulation of inflammation. The downregulation of inflammation was achieved by the binding of SAP15 to intracellular histone deacetylase (HDAC5). SAP15-mediated inhibition of inflammation was examined in vitro and in vivo using murine macrophages, human articular chondrocytes, and a collagen-induced arthritis (CIA) rat model. Surface plasmon resonance and immunoprecipitation assays indicated that SAP15 binds to HDAC5. SAP15 inhibited the lipopolysaccharide (LPS)-induced phosphorylation of intracellular HDAC5 and NF-κB p65 in murine macrophages. SAP15 treatment increased aggrecan and type II collagen expression and decreased osteocalcin expression in LPS-induced chondrocytes. Subcutaneous injection of SAP15-loaded sodium hyaluronic acid (HA) solution significantly decreased hind paw swelling, joint inflammation, and serum cytokine levels in CIA rats compared with the effects of sodium HA solution alone. The SAP15-loaded HA group exhibited preservation of cartilage and bone structure in CIA rat joints. Moreover, a more robust anti-inflammatory effect of the SAP15 loaded HA was observed than that of etanercept (an anti-tumor necrosis factor-alpha [TNF-α] antibody)-loaded HA. These findings suggest that SAP15 has an anti-inflammatory effect that is not controlled by sodium HA and is mediated by inhibiting HDAC5, unlike the anti-inflammatory mechanism of etanercept. These results demonstrate that SAP15 is useful as an inflammatory regulator of biomaterials and can be developed as a therapeutic for the treatment of inflammation.

Layer-by-layer coated silicone-based soft contact lens hydrogel for diclofenac sustained release

Introduction Soft contact lenses (SCLs) constitute a promising vehicle for ocular drug delivery due to their biocompatibility, prolonged contact with the eye and general acceptance. Soaking in the drug solution is the simplest method to load the drug into the SCLs. However, it usually does not ensure a controlled drug release, compatible with the therapeutic needs. Thus, additional approaches, such as the application of coatings on the SCLs that constitute a barrier to the drug release, have been tried to achieve that purpose [1]. The main goal of this work is to investigate the possibility of using a layer-by-layer (LbL) coating strategy, with alginate, chitosan and hyaluronic acid (ALG/CHI/HA) to get a controlled release of diclofenac from silicon based hydrogels. Materials and methods A lab-made silicon-based hydrogel intended for SCLs was loaded by soaking with the anti-inflammatory (diclofenac, DCF) and coated layer-by-layer (LbL) by immersion in solutions of alginate, chitosan and hyaluronic acid. Material properties such as transmittance, wettability, ionic permeability and swelling were studied. Drug release experiments were carried out under sink conditions (3 mL NaCl aqueous solution 130 mM, 36 °C, 180 rpm stirring). The coating stability and lysozyme-coating interaction was evaluated by quartz crystal microbalance with dissipation (QCM-D). A mathematical model was applied to predict the in vivo efficacy of the coated lenses. Chorioallantoic membrane (HET-CAM) tests were carried out to predict potential ocular irritation. Results The coating did not impair the studied physico-chemical properties, relevant for the application of the material in SCLs. HET-CAM tests did not suggest any potential for ocular irritation of both uncoated and coated samples. QCM-D data revealed the stability of the deposited layers and no adsorption of the protein. DCF release kinetics was controlled by the presence of the coating. The DCF concentration profile in the tear fluid estimated from the mathematical model predicts values above the half maximal inhibitory concentrations (IC50) for cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) during more than 2 weeks, for the coated hydrogels, while for the uncoated such levels are only expected in the first day of release. Discussion and conclusions ALG/CHI/HA LBL coated silicon hydrogels present adequate properties to be used in DCF releasing SCLs. They reveal an antifouling behaviour against lysozyme, one of the most abundant protein in lacrimal fluid. In vitro studies suggest that such system has potential to be used in the production of efficient therapeutic SCLs.

Triborheological Study under Physiological Conditions of PVA Hydrogel/HA Lubricant as Synthetic System for Soft Tissue Replacement.

In soft tissue replacement, hydrophilic, flexible, and biocompatible materials are used to reduce wear and coefficient of friction. This study aims to develop and evaluate a solid/liquid triborheological system, polyvinyl alcohol (PVA)/hyaluronic acid (HA), to mimic conditions in human synovial joints. Hydrogel specimens prepared via the freeze–thawing technique from a 10% (w/v) PVA aqueous solution were cut into disc shapes (5 ± 0.5 mm thickness). Compression tests of PVA hydrogels presented a Young’s modulus of 2.26 ± 0.52 MPa. Friction tests were performed on a Discovery Hybrid Rheometer DHR-3 under physiological conditions using 4 mg/mL HA solution as lubricant at 37 °C. Contact force was applied between 1 and 20 N, highlighting a coefficient of friction change of 0.11 to 0.31 between lubricated and dry states at 3 N load (angular velocity: 40 rad/s). Thermal behavior was evaluated by differential scanning calorimetry (DSC) in the range of 25–250 °C (5 °C/min rate), showing an endothermic behavior with a melting temperature (Tm) around 231.15 °C. Scanning Electron Microscopy (SEM) tests showed a microporous network that enhanced water content absorption to 82.99 ± 1.5%. Hydrogel achieved solid/liquid lubrication, exhibiting a trapped lubricant pool that supported loads, keeping low coefficient of friction during lubricated tests. In dry tests, interstitial water evaporates continuously without countering sliding movement friction.

Polymer effects on viscoelastic fluid flows in a planar constriction microchannel

A comprehensive understanding of the flow of viscoelastic polymer solutions in a contraction and/or an expansion geometry concerns numerous applications. The effects of polymer type, molecular weight, and concentration are investigated through controlled experiments with polyethylene oxide (PEO), polyvinylpyrrolidone (PVP) and hyaluronic acid (HA) solutions in a planar constriction microchannel in a wide range of Reynolds (Re) and Weissenberg (Wi) numbers. The polymer structure renders drastic differences amongst the contraction flows of 3000 ppm PEO, PVP, and HA solutions despite having similar molecular weights. The expansion flow vortices of these solutions remain analogous to those in the inertial flow of water. Increasing the molecular weight or concentration of PEO polymer promotes the elastic instabilities in both the contraction and expansion flows. It, however, suppresses (and even blocks) the inertial vortices in the expansion flow and makes them start from the salient corners, in contrast to the lips of the expansion walls in water. Interestingly, a sudden decrease in the size of inertial vortices is observed in the expansion flow of 500 ppm, 1 megadalton PEO solution when the elastic disturbances start appearing in the contraction flow. The observed flow regimes and vortex development in the polymer solutions are summarized in the same dimensionless Re−Wi and Re−χL parameter spaces, where χL is the normalized vortex length. The elasticity number, El=Wi/Re, is found to determine and distinguish the contraction and expansion flows.

Fibrin glue: Novel submucosal injection agent for endoscopic submucosal dissection.

Background and study aims Adequate mucosal elevation by submucosal injection is crucial for patient safety and efficiency during endoscopic submucosal dissection (ESD). This study aimed to evaluate the efficacy of fibrin glue (FG) as a long-lasting submucosal injection agent and to evaluate the technical feasibility of FG injection for ESD. Materials and methods To compare the capabilities of different agents in maintaining submucosal evaluation, we injected FG, hyaluronic acid solution, and normal saline into the porcine gastric specimen that was incised into approximately 5 × 5 cm squares. Then, we measured the height of submucosal elevations over time. Moreover, three hypothetical lesions from the resected porcine stomach underwent ESD with FG injection. Thereafter, we conducted macroscopic and histopathologic analyses. Results FG maintained the greatest submucosal elevation among all the injection agents. Three ESD procedures were performed with en bloc resection. Both macroscopic and histopathologic findings showed a thick FG clot on the ulcers. Conclusions The FG solution can be potentially used as an ESD submucosal injection agent in an in vitro model.

Rheological Properties of Cartilage Glycosaminoglycans and Proteoglycans

Glycosaminoglycans (GAGs) are molecules that govern the load-bearing and frictional properties of cartilage and the lubricating properties of synovial fluid of joints. Most GAGs in the body form proteoglycans (PGs), and the dominant PG in cartilage is the bottlebrush-shaped aggrecan, comprised of a protein core decorated by GAG side chains consisting mainly of chondroitin sulfate (CS) and keratan sulfate. Additionally, hyaluronic acid (HA) induces aggrecan to self-assemble into complexes having up to 100 aggrecan molecules attached to each HA chain “backbone”. Here, we report the rheological properties of CS, HA, aggrecan, and aggrecan–HA complexes in water and salt solutions. We find that CS solutions are viscous liquids, while HA solutions exhibit viscoelasticity and shear thinning. Specifically, in the case of HA, the storage modulus G′ exceeds the loss modulus G″ at high frequencies (ω) while the reverse is true at low ω. Thus, the rheologies of CS and HA exhibit somewhat distinct viscoelastic properties. Aggrecan, on the other hand, shows a rheology consistent with an incipient “weak gel” in which G′ and G″ cross at a specific ω and follow a power-law scaling over a wide ω range. Moreover, aggrecan samples do not attain an observable plateau in the viscosity under steady shear and low shear rates. Finally, the complexation of aggrecan and HA over a period of 48 h results in a slow evolution (“aging”) in measured rheological properties, with G′ at low ω progressively increases in time, while G″ remains essentially unchanged. This suggests that aggrecan and HA gradually form a macroscopic network in which molecular complexes act as physical cross-links.

Different Effects of Albumin and Hydroxyethyl Starch on Low Molecular-Weight Solute Permeation through Sodium Hyaluronic Acid Solution.

Hyaluronic acid (HA), a high-molecular-weight linear polysaccharide, restricts solute transport through the interstitial space. Albumin and hydroxyethyl starch (HES) solutions are used to correct the decrease of blood volume during surgery, but may leak into the interstitial space under inflammation conditions. Given the possibility that the structure of HA may be affected by adjacent macromolecules, this study tested whether albumin and HES (Mw 130,000) exert different effects on solute permeation through sodium hyaluronic acid (NaHA: Mw 1.3 × 106) solution. To this end, permeation of Orange G, a synthetic azo dye (Mw 452), into NaHA solutions containing albumin or HES over time was assessed. The amount of time it took for the relative absorbance of Orange G to reach 0.3 (T0.3) was determined in each NaHA solution relative to the reference solution (i.e., colloid solution without NaHA). Relative T0.3 values of albumin were larger than those of HES for 0.1% NaHA solution (3.33 ± 0.69 vs. 1.16 ± 0.08, p = 0.006, n = 3) and 0.2% NaHA solution (1.95 ± 0.32 vs. 0.92 ± 0.27, p = 0.013, n = 3). This finding may help in the selection of an appropriate colloid solution to control drug delivery into the interstitial space of cancer tissue under inflammation conditions.

Aloe vera-based antibacterial porous sponges for wound dressing applications

The antibacterial sponges with high macroporosity, high interconnectivity and high biocompatibility is a significant concern for wound healing applications. In this work, novel Aloe vera (AV) based sponges were developed via subsequent lyophilization with further chemical crosslinking throughout the double network sponges. Single network was composed of gelatin-sodium alginate (G-SA) while the double network using gelatin-sodium alginate- sodium hyaluronate (G-SA-HA) was produced with the addition of hyaluronic acid solution into the gelatin-sodium alginate matrix. Lastly, Aloe vera as the bioactive agent was fabricated throughout the gelatin-sodium alginate-sodium hyaluronate matrix. The AV-based sponges demonstrated large pores with high interconnectivity. The swelling degree of the AV-based sponges were higher than that of G-SA and G-SA-HA sponges. The release of AV from the sponges reached an equilibrium value after 24 h showing a more controlled release at pH 5.5 than at pH 7.4. AV-based sponges showed antibacterial activity against Staphylococcus aureus, Enterococcus faecalis, Streptococcus pneumoniae and Bacillus cereus and displayed any cytotoxicity against Mesenchymal stem cells.

Aesculus hippocastanum L. as a Stabilizer in Hemp Seed Oil Nanoemulsions for Potential Biomedical and Food Applications.

Nanoemulsion systems receive a significant amount of interest nowadays due to their promising potential in biomedicine and food technology. Using a two-step process, we produced a series of nanoemulsion systems with different concentrations of hemp seed oil (HSO) stabilized with Aesculus hippocastanum L. extract (AHE). Water and commercially-available low-concentrated hyaluronic acid (HA) were used as the liquid phase. Stability tests, including an emulsifying index (EI), and droplet size distribution tests performed by dynamic light scattering (DLS) proved the beneficial impact of AHE on the emulsion’s stability. After 7 days of storage, the EI for the water-based system was found to be around 100%, unlike the HA systems. The highest stability was achieved by an emulsion containing 5% HSO and 2 g/L AHE in water, as well as the HA solution. In order to obtain the detailed characteristics of the emulsions, UV-Vis and FTIR spectra were recorded, and the viscosity of the samples was determined. Finally, a visible microscopic analysis was used for the homogeneity evaluation of the samples, and was compared with the DLS results of the water system emulsion, which showed a desirable stability. The presented results demonstrate the possible use of oil emulsions based on a plant extract rich in saponins, such as AHE. Furthermore, it was found that the anti-inflammatory properties of AHE provide opportunities for the development of new emulsion formulations with health benefits.

Assessment of Non-cultured Autologous Epidermal Cell Grafting Resuspended in Hyaluronic Acid for Repigmenting Vitiligo and Piebaldism Lesions: A Randomized Clinical Trial.

The aim of this study was to assess the efficacy of non-cultured autologous epidermal cell grafting resuspended in hyaluronic acid, performed using a ready-to-use kit, compared with hyaluronic acid alone (neutral comparator) for repigmenting vitiligo and piebaldism lesions at 6 months. Two identified paired lesions per patient were randomized to be treated by either device. Devices with a ready-to-use kit were prepared by separate health professionals, to maintain blinding. A skin biopsy was digested using trypsin, and cells resuspended in hyaluronic acid solution. Among 38 patients screened, 36 (94.7%) patients, corresponding to 72 lesions, were analysed. For difficult-to-treat lesions, defined as those located on the wrist, elbow, and hands (n = 30), no repigmentation ≥50% was observed. For all other locations (n = 42), the success rate was significantly higher (p = 0.021) in the ready-to-use kit group (47.6% vs 9.5%) at 6 months and was maintained until 12 months. In conclusion, a single application of non-cultured epidermal cellular grafting using a ready-to-use kit was efficient at 6 months and at 1-year follow-up.

Production of Nanofiber Materials Based on Macromolecular Hyaluronic Acid by Electrospinning

Hyaluronic acid-based nanofiber scaffolds imitating the natural extracellular matrix, which is promising for use in tissue engineering, have been prepared by electrospinning. Hyaluronic acid is part of many organs and tissues; it is a biologically active component capable of being involved in cell proliferation and migration. The high viscosity of solutions of the macromolecular biopolymer significantly complicates the preparation of nanofiber scaffolds based on it. Rheological studies have made it possible to determine the solvent composition that contributes to a decrease in the viscosity of the spinning solution. The highest Newtonian viscosity of a 1% hyaluronic acid solution in water is 25 Pa s; in the case of using a mixture of ammonia hydrate (10%) and dimethylformamide at a ratio of 2 : 1, this parameter decreases to 1.147 Pa s. The use of a special spinning cell with a small-diameter nozzle and a high pressure (up to 10 atm) has provided the formation of hyaluronic acid-based nanofibers with a diameter of 100–300 nm.

Dynamic permeability of fluids in rectangular and square microchannels: Shift and coupling of viscoelastic bidimensional resonances

Pulsatile dynamics of Newtonian and Maxwellian fluids is exactly solved by theoretical analytical means when confined within rectangular microchannels subject to oscillatory driving forces. The analytical solution exhibits a complex behavior caused by the fluid dynamics along the smallest and the secondary confinement dimensions. For Newtonian fluids, the maximum and average flow velocities within the microchannel differ considerably from the ones predicted by simplified one-dimensional models when fluids are subject to moderate and high driving force frequencies. This is caused by the stagnation of flow velocity in the vicinity of the channel walls at the secondary confinement dimension. For Maxwellian fluids, the secondary confinement incorporates flow resonances that are coupled to the ones caused by the smallest confinement, leading to a shift of the main resonance and the arising of resonances when bidimensional vibration modes are excited. These effects depend on the aspect ratio between channel width and height and on the magnitude of the driving force frequency, compared to the characteristic viscous frequency of the microchannel. The theoretical results are compared with recent experimental results in the literature in pulsatile microfluidics for hyaluronic acid solutions with viscoelastic properties, as well as for water. In both cases, an agreement is found between theoretical and experimental results.

Electrosprayed Nanoparticles Based on Hyaluronic Acid: Preparation and Characterization

Modern drug delivery systems demand the development of targeted polymer-carriers with the set of obligatory requirements. Thus, such capsules must have total biocompatibility, biodegradability, and possess non-allergenic, and non-tumorigenic properties. Hyaluronic acid (HA), as a natural linear polysaccharide that is included in the pericellular and extracellular matrixes, satisfies all these demands in the best possible way. In this study, the biopolymer nanoparticles with an average diameter of 300 nm were successfully obtained from aqueous HA solutions by electrospraying technique and characterized. Due to the presence of active functional groups in the structure of HA, such polymer particles can incorporate various pharmaceutical agents. This finding expands the investigation and subsequent application of drug-loaded nanoparticles based on HA as challenging and advanced targeted delivery systems.

The Effects of Subcutaneously Injected Novel Biphasic Cross-Linked Hyaluronic Acid Filler: In Vivo Study.

Biphasic hyaluronic acid (HA) fillers have been used extensively to improve facial skin. However, in some cases, the skin surface is irregular because of the premature loss of HA solution. We propose a new biphasic filler (G-filler) to overcome this problem by using small particles of HA hydrogel instead of HA solution, which can provide a smooth skin surface and good durability. We evaluated the rheologic properties of G-filler and its physiologic effects after subcutaneous injection in a mouse model by histologic analysis. The G-filler showed a similar elastic modulus (G') and complex viscosity (η*) as the conventional biphasic filler, but had a higher viscous modulus (G″) than the conventional monophasic filler. The highest material elasticity (tan δ) value and the lowest percentage elasticity value indicate the rheologic properties of G-filler are closer to those of liquids. After subcutaneous injection of G-filler, collagen content (~ 2-fold) and elastin fibers (~ 6.5-fold) were significantly increased at 12weeks compared to those of the saline group. Fibronectin (~ 2.6-fold) and the laminin-immunolabeled cell number (~ 6-fold) were also significantly increased at 12weeks. Significant increases in the CD31-immunoreactive cell numbers of the G-filler groups were observed at 2, 6, and 12weeks (~ 3.7-fold) compared to those of the saline groups. There were no significant differences between the G-filler and saline groups in patterns of skin thickness and inflammatory cell numbers around loading sites. These findings demonstrate that the injection of a new biphasic filler with improved rheologic properties can effectively stimulate extracellular matrix production and angiogenesis without safety concerns. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors - www.springer.com/00266 .

Initial Leuprolide Acetate Release from Poly(d,l-lactide-co-glycolide) in Situ Forming Implants as Studied by Ultraviolet-Visible Imaging.

The initial drug release from in situ forming implants is affected by factors such as the physicochemical properties of the active pharmaceutical ingredient, the type of the excipients utilized, and the surrounding environment. The feasibility of UV-vis imaging for characterization of the initial behavior of poly(d,l-lactide-co-glycolide) (PLGA)/1-methyl-2-pyrrolidinone (NMP) in situ forming implants was investigated. The in vitro release of leuprolide acetate (LA) and implant formation in real time were monitored using dual-wavelength imaging at 280 and 525 nm, respectively, in matrices based on agarose gel and hyaluronic acid (HA) solution emulating the subcutaneous matrix. Three hours upon injection of the pre-formulation, approximately 15% of the total amount of LA administered was found in the agarose gel, while 5% was released from the implant into the HA solution. Concurrently, more extensive swelling of the implants in the HA solution as compared to implants in the agarose gel was observed. Transport of both LA and the solvent NMP was investigated using UV-vis imaging in a small-scale cell where the geometry of the formulation was controlled, showing a linear correlation between drug release and solvent escape. Light microscopy showed that the microstructures of the resulting implants in agarose gel and HA solution were different, which may be attributed to the different solvent exchange rates. UV imaging was also used to examine the interaction of LA with the release medium by characterizing the diffusion of LA in agarose gel, HA solution, and phosphate buffered saline. The reduced LA diffusivity in HA solution as compared to agarose gel and the LA distribution coefficient in the agarose gel-HA system indicated the presence of interactions between LA and HA. Our findings show that the external environment affects the solvent exchange kinetics for in situ forming implants in vitro, resulting in different types of initial release behavior. UV-vis imaging in combination with biorelevant matrices may offer an interesting approach in the development of in situ forming implant delivery systems.

Understanding the Dual Dilemma of Dry Eye and Glaucoma: An International Review.

Glaucoma-related ocular surface disease (G-OSD) is a significant, yet often underdiagnosed, ocular co-morbidity affecting 40% to 59% of glaucoma patients worldwide. Although the use of topical glaucoma medications represents a proven strategy to control the untoward effects of high intraocular pressure, this treatment can profoundly disrupt the homeostasis of the tear film. The cumulative effect of medications, preservatives, and excipients alter underlying cellular structures which results in tear film abnormalities and instability of the ocular surface. Furthermore, these chronic inflammatory changes have been shown to impact efficacy of glaucoma treatment, patient compliance with therapy and overall quality of life. The pathogenesis of G-OSD is multifactorial and involves a vicious self-perpetuating cycle of inflammatory cytokines and proteins. The diagnosis of such disease is based on similar tests used in assessing traditional dry eye, taking into consideration findings specific to this patient population. The hallmark of treatment for these patients is to minimize the ocular surface inflammatory response by choosing glaucoma therapies that spare the ocular surface such as preservative free formulations and initiating dry eye treatment early in the course of care. In summary, glaucoma affects millions of patients around the world and chronic use of topical glaucoma medications may negatively impact the patient's ocular surface, symptoms, and vision. Understanding the pathogenesis of G-OSD, recognizing its risk factors and incorporating diagnostic and therapeutic strategies that restore and maintain ocular surface homeostasis will result in improved care for our patients.

Are Injections of Platelet-Rich Plasma Overused in Knee Osteoarthritis Despite Their Unproven Effectiveness?

Objective: To clarify whether intra-articular injections of platelet-rich plama (PRP) are really effective for pain management in knee osteoarthritis. Methods: In this article, we have performed a narrative review of recent literature (2018-2019) to clarify whether intra-articular injections of PRP are truly effective. Results: A study with an evidence level of 1 that compared the long-term (5 years) clinical results of intra-articular injections of PRP versus hyaluronic acid (HA) in knee osteoarthritis showed that both treatments were effective in improving the knee’s functional status. PRP did not provide superior clinical improvement over HA in terms of the duration of the effect or symptom-functional improvement at various points during the follow-up. The mean duration of the patient’s subjective perception of pain relief was 9 months with HA and 12 months with PRP (no significant difference). Another trial with an evidence level of 1 compared the efficacy of intra-articular injections of leukocyte-poor PRP, HA and normal saline solution (sham control group) in mild-moderate knee osteoarthritis. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score and the International Knee Documentation Committee (IKDC) subjective score were obtained at the start of the study and at 1, 2, 6 and 12 months after treatment. The 3 groups showed statistically significant improvements in the outcome measures at 1 month; however, only the PRP group maintained significant improvement in both the WOMAC score and the IKDC score at 12 months. Conclusions: Although promising initial results from the use of PRP have been published, most of the studies with an evidence level of 1 have had numerous problems, including small sample sizes, potentially inappropriate control cohorts and short follow-ups. Despite these limitations, there is still evidence to justify the use of PRP in treating knee osteoarthritis. However, further high-level human studies using standardized protocols are needed.