Evaluation of the Effect of Pomegranate Seed Oil on Healing in a Rat Wound Model With Antioxidant, Vascular, and Histopathological Parameters

The study aimed to evaluate the efficiency of pomegranate (Punica granatum) seed oil in wound healing in excised rats. Sixteen female young Wistar Albino Rats weighing approximately 300 to 320 g were randomly divided into 2 groups as the treatment (=pomegranate seed oil group) and control groups in this experiment. Six different wounds 1 cm apart from the midline and each other were formed with a 6 mm punch biopsy instrument. Three wounds were left open (open wound group) whereas 3 wounds were sutured with 4/0 vicryl (closed wound group). Punica granatum seed oil treatment was administered topically to the treatment group, both to open and closed wounds, once a day for 14 days. Parameters for healing were evaluated. Histopathologic examination was performed for the investigation of inflammation, neovascularization, granulation, and fibroblast generation in addition to serologic (enzyme-linked immunosorbent assay) evaluation of rat malondialchehyche, rat glutathione peroxidase, and rat superoxide dismutase. PeriScan PIM 3 System Laser Doppler Blood Perfusion Imager was used for the calculation of blood perfusion. There was a statistically significant difference between inflammation and neovascularization levels and group type on the 14th day in open wounds(P < .05). On the 21st day, the granulation tissue level in the closed wound group was found to be higher in the pomegranate group (P = 0.000).The results showed that PSE oil is partially effective, although it is not effective in every parameter examined, in the treatment of excised wounds in rats and may be suitable for clinical treatment in humans but large controlled studies are needed.

Effect of Sodium Hypochlorite 0.05% on MMP-9 Extracellular Release in Chronic Wounds

BACKGROUND

In chronic wounds, high concentrations of matrix metalloproteinases (MMPs) can cause excessive proteolysis and slow wound healing. Consequently, restoring a proper MMP balance can help reduce the risk of a chronic wound. An antiseptic solution containing 0.05% sodium hypochlorite (Amukine Med 0.05%, Angelini S.p.A.; hereafter termed NaClO solution) is available on the market. The NaClO solution was proven effective and safe in managing infected skin wounds. To further characterize its activity, this study evaluated the in vitro activity of the NaClO solution on the monocyte release of MMPs.

METHODS

Human monocytic THP-1 (ATCC^® TIB-202™) cell lines were differentiated into macrophages and treated with different concentrations of NaClO (from 0.05% to 5 × 10^-7%). In addition, the THP-1 cell line was stimulated with wound fluid (WF) from patients with active venous leg ulcers in the inflammatory phase. The effect of NaClO (0.025-0.0062%) was also evaluated on healthy human peripheral blood serum samples. The effects of treatments on the gelatinolytic activity of MMP-9 were evaluated by gelatin zymography. The effects on MMPs release were evaluated through the Pro™ Human MMP 9-plex Assay. An exploratory scratch wound healing assay was also performed.

RESULTS

The NaClO solution reduced the gelatinolytic activity of MMP-9 and its activated form. The downregulation of MMP-9 gelatinolytic activity was also observed in peripheral blood serum. The MMPs profile showed a reduction in MMP-1 release (p < 0.05) and a slight reduction of the release of MMP-9 and MMP-12 after the treatment with LPS and the NaClO solution. A slight improvement in wound healing was observed after macrophage activation and treatment with the NaClO solution.

CONCLUSIONS

The results obtained suggest a possible ability of the NaClO solution to modulate the proteolytic pathways in the wound microenvironment, further characterizing its activity and use in clinical practice during wound care.

FBN2 Silencing Recapitulates Hypoxic Conditions and Induces Elastic Fiber Impairment in Human Dermal Fibroblasts

Most chronic wounds are characterized by varying degrees of hypoxia and low partial pressures of O2 that may favor the development of the wound and/or delay healing. However, most studies regarding extracellular matrix remodeling in wound healing are conducted under normoxic conditions. Here, we investigated the consequences of hypoxia on elastic network formation, both in a mouse model of pressure-induced hypoxic ulcer and in human primary fibroblasts cultured under hypoxic conditions. In vitro, hypoxia inhibited elastic fiber synthesis with a reduction in fibrillin-2 expression at the mRNA and protein levels. Lysyl oxidase maturation was reduced, concomitant with lower enzymatic activity. Fibrillin-2 and lysyl oxidase could interact directly, whereas the downregulation of fibrillin-2 was associated with deficient lysyl oxidase maturation. Elastic fibers were not synthesized in the hypoxic inflammatory tissues resulting from in vivo pressure-induced ulcer. Tropoelastin and fibrillin-2 were expressed sparsely in hypoxic tissues stained with carbonic anhydrase IX. Different hypoxic conditions in culture resulted in the arrest of elastic fiber synthesis. The present study demonstrated the involvement of FBN2 in regulating elastin deposition in adult skin models and described the specific impact of hypoxia on the elastin network without consequences on collagen and fibronectin networks.

Oxygen, pH, Lactate, and Metabolism-How Old Knowledge and New Insights Might Be Combined for New Wound Treatment

Over time, we have come to recognize a very complex network of physiological changes enabling wound healing. An immunological process enables the body to distinguish damaged cells and begin a cleaning mechanism by separating damaged proteins and cells with matrix metalloproteinases, a complement reaction, and free radicals. A wide variety of cell functions help to rebuild new tissue, dependent on energy provision and oxygen supply. Like in an optimized “bio-reactor,” disturbance can lead to prolonged healing. One of the earliest investigated local factors is the pH of wounds, studied in close relation to the local perfusion, oxygen tension, and lactate concentration. Granulation tissue with the wrong pH can hinder fibroblast and keratinocyte division and proliferation, as well as skin graft takes. Methods for influencing the pH have been tested, such as occlusion and acidification by the topical application of acidic media. In most trials, this has not changed the wound’s pH to an acidic one, but it has reduced the strong alkalinity of deeper or chronic wounds. Energy provision is essential for all repair processes. New insights into the metabolism of cells have changed the definition of lactate from a waste product to an indispensable energy provider in normoxic and hypoxic conditions. Neovascularization depends on oxygen provision and lactate, signaling hypoxic conditions even under normoxic conditions. An appropriate pH is necessary for successful skin grafting; hypoxia can change the pH of wounds. This review describes the close interconnections between the local lactate levels, metabolism, healing mechanisms, and pH. Furthermore, it analyzes and evaluates the different possible ways to support metabolism, such as lactate enhancement and pH adjustment. The aim of wound treatment must be the optimization of all these components. Therefore, the role of lactate and its influence on wound healing in acute and chronic wounds will be assessed.

Local and Systemic Expression Pattern of MMP-2 and MMP-9 in Complex Regional Pain Syndrome

Matrix metalloproteinases (MMP)-2 and MMP-9 play important roles in inflammation as well as in pain processes. For this reason, we compared the concentrations of these enzymes in skin and serum of patients with complex regional pain syndrome (CRPS), other pain diseases and healthy subjects. We analyzed ipsi- and contralateral skin biopsies of 18 CRPS patients, as well as in 10 pain controls and 9 healthy subjects. Serum samples were analyzed from 20 CRPS, 17 pain controls and 17 healthy subjects. All samples were analyzed with ELISA. Concentrations were then compared to clinical data as well as to quantitative sensory testing data.MMP-2 was increased in both ipsi- and contralateral skin biopsies of CRPS patients compared to healthy subjects. While low ipsilateral MMP-2 was associated with trophic changes, contralateral MMP-2 inversely correlated with the CRPS severity. MMP-9 was also locally increased in ipsilateral CRPS skin, and higher ipsi- and contralateral MMP-9 levels correlated with CRPS severity. We conclude that MMP-2 and MMP-9 are differently expressed depending on the clinical phenotype in CRPS. PERSPECTIVE: This article describes an upregulation of MMPs in CRPS and pain controls and shows different expression of MMP-2 and -9 depending on clinical phenotype in CRPS. These results provide evidence that MMP-2 and -9 play a key role in CRPS pathophysiology.

Targeting MMP-9 in Diabetic Foot Ulcers

Diabetic foot ulcers (DFUs) are significant complications of diabetes and an unmet medical need. Matrix metalloproteinases (MMPs) play important roles in the pathology of wounds and in the wound healing process. However, because of the challenge in distinguishing active MMPs from the two catalytically inactive forms of MMPs and the clinical failure of broad-spectrum MMP inhibitors in cancer, MMPs have not been a target for treatment of DFUs until recently. This review covers the discovery of active MMP-9 as the biochemical culprit in the recalcitrance of diabetic wounds to healing and targeting this proteinase as a novel approach for the treatment of DFUs. Active MMP-8 and MMP-9 were observed in mouse and human diabetic wounds using a batimastat affinity resin and proteomics. MMP-9 was shown to play a detrimental role in diabetic wound healing, whereas MMP-8 was beneficial. A new class of selective MMP-9 inhibitors shows clinical promise for the treatment of DFUs.

Protease activity as a prognostic factor for wound healing in venous leg ulcers

BACKGROUND

Venous leg ulcers (VLUs) are a common type of complex wound that have a negative impact on people's lives and incur high costs for health services and society. It has been suggested that prolonged high levels of protease activity in the later stages of the healing of chronic wounds may be associated with delayed healing. Protease modulating treatments have been developed which seek to modulate protease activity and thereby promote healing in chronic wounds.

OBJECTIVES

To determine whether protease activity is an independent prognostic factor for the healing of venous leg ulcers.

SEARCH METHODS

In February 2018, we searched the following databases: Cochrane Central Register of Controlled Trials (CENTRAL), Ovid MEDLINE, Ovid Embase and CINAHL.

SELECTION CRITERIA

We included prospective and retrospective longitudinal studies with any follow-up period that recruited people with VLUs and investigated whether protease activity in wound fluid was associated with future healing of VLUs. We included randomised controlled trials (RCTs) analysed as cohort studies, provided interventions were taken into account in the analysis, and case-control studies if there were no available cohort studies. We also included prediction model studies provided they reported separately associations of individual prognostic factors (protease activity) with healing. Studies of any type of protease or combination of proteases were eligible, including proteases from bacteria, and the prognostic factor could be examined as a continuous or categorical variable; any cut-off point was permitted. The primary outcomes were time to healing (survival analysis) and the proportion of people with ulcers completely healed; the secondary outcome was change in ulcer size/rate of wound closure. We extracted unadjusted (simple) and adjusted (multivariable) associations between the prognostic factor and healing.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for inclusion at each stage, and undertook data extraction, assessment of risk of bias and GRADE assessment. We collected association statistics where available. No study reported adjusted analyses: instead we collected unadjusted results or calculated association measures from raw data. We calculated risk ratios when both outcome and prognostic factor were dichotomous variables. When the prognostic factor was reported as continuous data and healing outcomes were dichotomous, we either performed regression analysis or analysed the impact of healing on protease levels, analysing as the standardised mean difference. When both prognostic factor and outcome were continuous data, we reported correlation coefficients or calculated them from individual participant data.We displayed all results on forest plots to give an overall visual representation. We planned to conduct meta-analyses where this was appropriate, otherwise we summarised narratively.

MAIN RESULTS

We included 19 studies comprising 21 cohorts involving 646 participants. Only 11 studies (13 cohorts, 522 participants) had data available for analysis. Of these, five were prospective cohort studies, four were RCTs and two had a type of case-control design. Follow-up time ranged from four to 36 weeks. Studies covered 10 different matrix metalloproteases (MMPs) and two serine proteases (human neutrophil elastase and urokinase-type plasminogen activators). Two studies recorded complete healing as an outcome; other studies recorded partial healing measures. There was clinical and methodological heterogeneity across studies; for example, in the definition of healing, the type of protease and its measurement, the distribution of active and bound protease species, the types of treatment and the reporting of results. Therefore, meta-analysis was not performed. No study had conducted multivariable analyses and all included evidence was of very low certainty because of the lack of adjustment for confounders, the high risk of bias for all studies except one, imprecision around the measures of association and inconsistency in the direction of association. Collectively the research indicated complete uncertainty as to the association between protease activity and VLU healing.

AUTHORS' CONCLUSIONS

This review identified very low validity evidence regarding any association between protease activity and VLU healing and there is complete uncertainty regarding the relationship. The review offers information for both future research and systematic review methodology.

Matrix metalloproteinases: The sculptors of chronic cutaneous wounds

Cutaneous wound healing is a complex mechanism with multiple processes orchestrating harmoniously for structural and functional restoration of the damaged tissue. Chronic non-healing wounds plagued with infection create a major healthcare burden and is one of the most frustrating clinical problems. Chronic wounds are manifested by prolonged inflammation, defective re-epithelialization and haphazard remodeling. Matrix metalloproteinases (MMPs) are zinc dependent enzymes that play cardinal functions in wound healing. Understanding the pathological events mediated by MMPs during wound healing may pave way in identifying novel drug targets for chronic wounds. Here, we discuss the functions and skewed regulation of different MMPs during infection and chronic tissue repair. This review also points out the potential of MMPs and their inhibitors as therapeutic agents in treating chronic wounds during distinct phases of the wound healing. This article is part of a Special Issue entitled: Proteolysis as a Regulatory Event in Pathophysiology edited by Stefan Rose-John.

Differential regulation of skin fibroblasts for their TGF-β1-dependent wound healing activities by biomimetic nanofibers

Nanofibers with different compositions differentially regulate fibroblast phenotypes in a TGF-β1 rich milieu through the integrin-mediated TGF-β1/Smad signaling pathway.

In vitro glycation of an endothelialized and innervated tissue-engineered skin to screen anti-AGE molecules

Glycation is one of the major processes responsible for skin aging through induction of the detrimental formation of advanced glycation end-products (AGEs). We developed an innovative tissue-engineered skin combining both a capillary-like and a nerve networks and designed a protocol to induce continuous AGEs formation by a treatment with glyoxal. We determined the optimal concentration of glyoxal to induce AGEs formation identified by carboxymethyl-lysin expression while keeping their toxic effects low. We showed that our tissue-engineered skin cultured for 44 days and treated with 200 μm glyoxal for 31 days displayed high carboxymethyl-lysine expression, which induced a progressively increased alteration of its capillary and nerve networks between 28 and 44 days. Moreover, it produced an epidermal differentiation defect evidenced by the lack of loricrin and filaggrin expression in the epidermis. These effects were almost completely prevented by addition of aminoguanidine 1.5 mm, an anti-glycation compound, and only slightly decreased by alagebrium 500 μm, an AGE-breaker molecule. This tissue-engineered skin model is the first one to combine a capillary and nerve network and to enable a continuous glycation over a long-term culture period. It is a unique tool to investigate the effects of glycation on skin and to screen new molecules that could prevent AGEs formation.

Wound samples: moving towards a standardised method of collection and analysis

Chronic wounds, including diabetic foot ulcers, pressure ulcers and venous leg ulcers, impact the lives of millions of people worldwide. These types of wounds represent a significant physical, social and financial burden to both patients and health care systems. Wound care has made great progress in recent years as a result of the critical research performed in academic, clinical and industrial settings. However, there has been relatively little translation of basic research discoveries into novel and effective treatments. One underlying reason for this paucity may be inconsistency in the methods of wound analysis and sample collection, resulting in the inability of researchers to accurately characterise the healing process and compare results from different studies. This review examines the various types of analytical methods being used in wound research today with emphasis on sampling techniques, processing and storage, and the findings call forth the wound care research community to standardise its approach to wound analysis in order to yield more robust and comparable data sets.

In vivo assessment of protease dynamics in cutaneous wound healing by degradomics analysis of porcine wound exudates

Proteases control complex tissue responses by modulating inflammation, cell proliferation and migration, and matrix remodeling. All these processes are orchestrated in cutaneous wound healing to restore the skin's barrier function upon injury. Altered protease activity has been implicated in the pathogenesis of healing impairments, and proteases are important targets in diagnosis and therapy of this pathology. Global assessment of proteolysis at critical turning points after injury will define crucial events in acute healing that might be disturbed in healing disorders. As optimal biospecimens, wound exudates contain an ideal proteome to detect extracellular proteolytic events, are noninvasively accessible, and can be collected at multiple time points along the healing process from the same wound in the clinics. In this study, we applied multiplexed Terminal Amine Isotopic Labeling of Substrates (TAILS) to globally assess proteolysis in early phases of cutaneous wound healing. By quantitative analysis of proteins and protein N termini in wound fluids from a clinically relevant pig wound model, we identified more than 650 proteins and discerned major healing phases through distinctive abundance clustering of markers of inflammation, granulation tissue formation, and re-epithelialization. TAILS revealed a high degree of proteolysis at all time points after injury by detecting almost 1300 N-terminal peptides in ∼450 proteins. Quantitative positional proteomics mapped pivotal interdependent processing events in the blood coagulation and complement cascades, temporally discerned clotting and fibrinolysis during the healing process, and detected processing of complement C3 at distinct time points after wounding and by different proteases. Exploiting data on primary cleavage specificities, we related candidate proteases to cleavage events and revealed processing of the integrin adapter protein kindlin-3 by caspase-3, generating new hypotheses for protease-substrate relations in the healing skin wound in vivo. The data have been deposited to the ProteomeXchange Consortium with identifier PXD001198.

High matrix metalloproteinase levels are associated with dermal graft failure in diabetic foot ulcers

The aim of our study is to analyze factors, including matrix metalloproteinase (MMP) levels, that could influence the integration of dermal grafts in diabetic foot ulcers. From September 2012 to September 2013, 35 diabetic patients with IIA lesion (Texas Wound Classification) and an extensive foot tissue loss were considered suitable for dermal graft. Before the enrollment we ensured the best local conditions: adequate blood supply, control of infection, and offloading. The MMP level of each lesion was evaluated blindly before the application of dermal substitutes. At 1-month follow-up, we analyzed the correlation between clinical patient characteristics, local wound features including MMP levels, dermal substitute applied, and the outcome expressed in terms of dermal graft integration. We observed dermal graft integration in 28/35 patients (80% of our population). In multivariate analysis high MMP level was the only negative predictor for dermal graft integration (P < .0007). In addition, we divided the patients into 2 groups according to MMP levels: group 1 with low protease activity (24 patients) and group 2 with elevated protease activity (11 patients). The integration of the dermal graft was 100% in group 1 (n = 24 patients) and 36.4% in group 2 (n = 4patients), P < .0001. According to our data, the evaluation of MMP levels may be useful to choose the right strategy to get the best results in terms of clinical success and cost saving. However, further studies are necessary to confirm these findings.

Back to basics: histological, microbiological and biochemical sampling in wound care

Despite the advances in our understanding of normal and abnormal wound healing over the past decade, a specific biomarker which can be used clinically to identify 'hard-to-heal' wounds still remains elusive. Tissue and exudate samples extracted from the site of the wound are traditionally analysed using histological, microbiological and biochemical laboratory techniques. The aim of this paper is to review the advantages of these techniques, their limitations and the rapid developments in the fields of microbiology and proteomics, which are offering new insights into the differences between healing and non-healing wounds.

Role of matrix metalloproteinases in non-healing venous ulcers

Chronic venous ulceration (CVU) of the lower limbs is a common condition affecting 1% of the adult population in Western countries, which is burdened with a high complication rate and a marked reduction in the quality of life often due to prolonged healing time. Several metalloproteinases (MMPs) such as MMP-9 together with neutrophil gelatinase-associated lipocalin (NGAL) appear to be involved in the onset and healing phases of venous ulcer, but it is still unclear how many biochemical components are responsible for prolonged healing time in those ulcers. In this study, we evaluate the role of MMP-1 and MMP-8 in long lasting and refractory venous ulcers. In a 2-year period we enroled 45 patients (28 female and 17 male, median age 65) with CVU. The enroled population was divided into two groups: group I were patients with non-healing ulcers (ulcers that had failed to heal for more than 2 months despite appropriate treatments) and group II were patients with healing ulcers (ulcers in healing phases). MMP-1 and MMP-8 were measured in fluids and tissues of healing and non-healing ulcers by means of enzyme-linked immunosorbent assay (ELISA) and Western blot analysis, respectively. In particular the patterns of the collagenases MMP-1 and MMP-8 in healing wounds were distinct, with MMP-8 appearing in significantly greater amounts especially in the non-healing group. Our findings suggest that MMP-1, and MMP-8 are overexpressed in long lasting CVU. Therefore, this dysregulation may represent the main cause of the pathogenesis of non-healing CVU.

A pre-clinical functional assessment of an acellular scaffold intended for the treatment of hard-to-heal wounds

The majority of the population experience successful wound-healing outcomes; however, 1-3% of those aged over 65 years experience delayed wound healing and wound perpetuation. These hard-to-heal wounds contain degraded and dysfunctional extracellular matrix (ECM); yet, the integrity of this structure is critical in the processes of normal wound healing. Here, we evaluated a novel synthetic matrix protein for its ability to act as an acellular scaffold that could replace dysfunctional ECM. In this regard, the synthetic protein was subjected to adsorption and diffusion assays using collagen and human dermal tissues; evaluated for its ability to influence keratinocyte and fibroblast attachment, migration and proliferation and assessed for its ability to influence in vivo wound healing in a porcine model. Critically, these experiments demonstrate that the matrix protein adsorbed to collagen and human dermal tissue but did not diffuse through human dermal tissue within a 24-hour observation period, and facilitated cell attachment, migration and proliferation. In a porcine wound-healing model, significantly smaller wound areas were observed in the test group compared with the control group following the third treatment. These data provide evidence that the synthetic matrix protein has the ability to function as an acellular scaffold for wound-healing purposes.

Ovine forestomach matrix biomaterial is a broad spectrum inhibitor of matrix metalloproteinases and neutrophil elastase

Proteases play a critical role in the ordered remodelling of extracellular matrix (ECM) components during wound healing and tissue regeneration. However, the usually ordered proteolysis is compromised in chronic wounds due to over-expression and high concentrations of matrix metalloproteinase's (MMPs) and neutrophil elastase (NE). Ovine forestomach matrix (OFM) is a decellularised extracellular matrix-based biomaterial developed for tissue regeneration applications, including the treatment of chronic wounds, and is a heterogeneous mixture of ECM proteins and proteoglycans that retains the native structural and functional characteristics of tissue ECM. Given the diverse molecular species present in OFM, we hypothesised that OFM may contain components or fragments that inhibit MMP and NE activity. An extract of OFM was shown to be a potent inhibitor of a range of tissue MMPs (IC50 s = 23 ± 5 to 115 ± 14 µg/ml) and NE (IC50 = 157 ± 37 µg/ml), and was more potent than extracts prepared from a known protease modulating wound dressing. The broad spectrum activity of OFM against different classes of MMPs (i.e. collagenases, gelatinases and stromelysins) may provide a clinical advantage by more effectively addressing the protease imbalance seen in chronic wounds.

Lipoxin A₄ inhibits platelet-activating factor inflammatory response and stimulates corneal wound healing of injuries that compromise the stroma

Platelet-activating factor (PAF) is a bioactive lipid mediator with strong inflammatory properties. PAF induces the expression and activation of metalloproteinase-9 (MMP-9) in corneal epithelial cells and myofibroblasts, and delays epithelial wound healing in an organ culture system. Lipoxin A(4) (LXA(4)) is a lipid mediator involved in resolution of inflammation and cornea epithelial wound healing. We developed an in vivo mouse model of injury to the anterior stroma that is sustained by PAF and evaluated the action of LXA(4). In this model mice were treated with vehicle, PAF alone and in combination with PAF receptor antagonist LAU-0901 or LXA(4). Mice were euthanized 1, 2 and 7 days after injury and corneas were processed for histology (H&E staining) and immunofluorescence with antibodies for MMP-9, α-smooth muscle actin (α-SMA), fibronectin (FN) and neutrophil. Interleukin 1-α (IL-1α) and keratinocyte-derived chemokine (KC/CXCL1) were assayed by ELISA. Myeloperoxidase (MPO) activity was performed in corneal homogenates. In this in vivo model PAF inhibited epithelial wound healing that was blocked by the PAF receptor antagonist LAU-0901. Treatment with LXA(4) significantly reduced the injured area compared to PAF at 1 and 2 days of treatment. The strong stromal cell infiltration and MPO activity stimulated by PAF was also decreased with LXA(4) treatment. PAF increased MMP-9 and decreased FN expression compared to vehicle treatment and less α-SMA positive cells migrated to the wounded area. The PAF actions were reverted by LXA(4) treatment. The results demonstrated a powerful action of LXA(4) in protecting corneas with injuries that compromise the stroma by decreasing inflammation and increasing wound healing.

Online electrospray ionization mass spectrometric monitoring of protease-catalyzed reactions in real time

Although there are a lot of well established methods for monitoring enzyme-catalyzed reactions, most of them are based on changes in spectroscopic properties during the conversion of substrates to products. However, reactions without optical changes are common, which are inapplicable to these spectroscopic methods. As an alternative technique for enzymologic research, mass spectrometry (MS) is favored due to its specificity, sensitivity, and the ability to obtain stoichiometric information. In this work, probe electrospray ionization (PESI) source coupled with a time of flight mass spectrometer was employed to monitor some typical protease-catalyzed reactions, including pepsinolysis and trypsinolysis of cytochrome c in real time. Due to the high electrical conductivity of each reaction system, corona discharges are likely to occur, which would decrease intensities of mass spectrometric signals. An ultra-fine sampling probe and an auxiliary vapor spray were adopted to prevent corona discharges. Experimental results from peptic and tryptic digestions of cytochrome c showed different and characteristic catalytic pathways. With the data presented in this study, PESI-MS can be considered as a potential tool for real-time monitoring of enzymatic reactions because of its simplicity in instrumental configuration, wide applicability under harsh conditions, and flexibility in combination with other techniques.

Doxycycline hydrogels with reversible disulfide crosslinks for dermal wound healing of mustard injuries

Doxycycline hydrogels containing reversible disulfide crosslinks were investigated for a dermal wound healing application. Nitrogen mustard (NM) was used as a surrogate to mimic the vesicant effects of the chemical warfare agent sulfur mustard. An 8-arm-poly(ethylene glycol) (PEG) polymer containing multiple thiol (-SH) groups was crosslinked using hydrogen peroxide (H(2)O(2) hydrogel) or 8-arm-S-thiopyridyl (S-TP hydrogel) to form a hydrogel in situ. Formulation additives (glycerin, PVP and PEG 600) were found to promote dermal hydrogel retention for up to 24 h. Hydrogels demonstrated high mechanical strength and a low degree of swelling (< 1.5%). Doxycycline release from the hydrogels was biphasic and sustained for up to 10-days in vitro. Doxycycline (8.5 mg/cm(3)) permeability through NM-exposed skin was elevated as compared to non vesicant-treated controls at 24, 72 and 168 h post-exposure with peak permeability at 72 h. The decrease in doxycycline permeability at 168 h correlates to epidermal re-epithelialization and wound healing. Histology studies of skin showed that doxycycline loaded (0.25% w/v) hydrogels provided improved wound healing response on NM-exposed skin as compared to untreated skin and skin treated with placebo hydrogels in an SKH-1 mouse model. In conclusion, PEG-based doxycycline hydrogels are promising for dermal wound healing application of mustard injuries.