Non-degraded Conditions Research Articles

Influences of cognitive load on sensorimotor contributions to working memory: An EEG investigation of mu rhythm activity during speech discrimination.

Sensorimotor activity during speech perception is highly variable and is thought to be related to the underlying cognitive processes recruited to meet task demands. The purpose of the current study was to evaluate the impact of cognitive load on sensorimotor-based attention and working memory processes during speech perception. Manipulations of set size and signal clarity were employed to alter cognitive load. Raw EEG data recorded from 42 subjects during accurate discrimination of CV syllable pairs were decomposed by Independent component analysis; identifying sensorimotor mu components from 37 subjects. Time-frequency analyses revealed event related desynchronization (ERD) across alpha and beta frequency bands during and following stimulus presentation in all conditions, reflecting working memory maintenance through covert articulatory rehearsal. No early attentional activity was observed, suggesting adaptation to tasks. However, modulation of late working memory activity was observed between degraded and non-degraded conditions. Weak and delayed alpha and beta ERD in degraded conditions were interpreted as evidence of delayed implementation of covert rehearsal due to the prolonged time necessary to extract a phonological representation from the auditory signal. Findings are interpreted within Analysis by Synthesis to characterize the multi-faceted and temporally distinct contributions of anterior sensorimotor regions to working memory in support of speech discrimination.

Degradation of Non-Photosynthetic Vegetation in a Semi-Arid Rangeland

Land degradation in drylands is the process in which undesirable conditions emerge due to human and natural causes. Despite the particularly deleterious effects of degradation, and it’s potentially irreversible nature, regional assessments have provided conflicting extents, rates, and severities of degradation, both globally and regionally. Current monitoring of degradation relies upon the detection of green, photosynthetically active parts of vegetation (e.g., leaves). Less is known, however, about the effect of degradation on the non-photosynthetic components of vegetation (e.g., wood, stems, leaf litter) and the relationship between photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV), and bare soil under degraded conditions (BS). The major objective of the study was to evaluate regional patterns of fractional cover (i.e., PV, NPV, BS) under degraded and non-degraded NPP conditions in a managed rangeland in north Queensland, Australia. Homogenous environmental conditions were identified and each of NPP, PV, NPV, and BS were scaled according to their potential, reference values. We found a strong spatial and temporal correlation between scaled NPP with both scaled PV and scaled BS. Drastic differences were also found for PV and BS between degraded and non-degraded conditions. NPV displayed similarity to both PV and BS, however no clear relationship was found for NPV in all areas, irrespective of degradation conditions.

The evolution of podzolized and regraded chernozems in Eastern Upland Wooded Steppe of Ukraine and the ways of their development

It is indicated that podzolized and regarded chernozems in moderately humid and arid zones of Left-bank Wooded steppe with HTC 1,2–1,0 (within the valleys of the Sula and Oskil rivers) occur in high watersheds along right bedrock banks of the valleys, adjoining or being included into wooded refugiums. Being formed by the grove biogeocenosis, they have high rates of fertility. The morphological research of natural podzolized chernozems profiles showed, that the upper humus slightly-eluviated horizon, densely interweaved by roots, has coarse agronomically valuable structure, loose composition, dark-grey colour, that indicates high content of humus. It is mostly favoured by the biologically active, rich in calcium ground litter and the pristinity of soil texture. The general capacity of the humus profile is not less than 100 cm. While brining natural soils into tillage some changes of soil development conditions arise. They are: hydrothermic conditions, secondary carbonate enrichment (regradation), loosening of illuvial horizon. Under mechanical tillage the granular structure changes into a pulverescent and cloddy one, the topsoil becomes lighter because of humus loss, though the humus profile becomes 10–20 cm deeper. The analytical results indicate the sufficient differences in physicochemical and agrochemical characteristics between forest podzolized chernozems and their regradated analogs in tillage. Natural soils contain 5,7–6,5 % of humus in upper 0–35 cm layer, and up to 10,0 % in 0–15 cm layer. They also have considerable resources of hydrolyzable nitrogen. In agrogenic soils the humus content is up to 3,6 %. The humus is of a humate type both in podzolized and regarded soils. The smallest proportion of Сh.a./Сf.a is in the lower layer of humus eluviated horizon of forest soils. The level of humus loss by agrogenic soils in humus slightly-eluviated layer fluctuates from 37 % to 44 %. Dark-grey and grey forest soils lose more than half of humus content, typical chernozems – nearly 30 %, ordinary chernozems – 20 %. Regraded analogs are inferior according to the hydrolyzable nitrogen content. Positive evolutional changes in tillage, such as acidity reduction, bases saturation growth, illuvium destruction, didn’t yield expected results – resistance to degradation processes. For the development of agrogenic soils it is necessary to implement flexible complex systems of husbandry with minimal intensity of tillage, adapted to the landscape, bringing the culture of husbandry closer to natural conditions. Promising is the implementation of soil protection technologies with the maximum use of freak produce of plant growing. The integrity of soil composition and biologically active layer of mulch create the conditions, close to virgin ones, that lead to the transition of soil to natural non-degradation conditions without losing its productive functions.

Age-related differences in associative memory: the role of sensory decline.

Numerous studies show age-related decline in episodic memory. One of the explanations for this decline points to older adults' deficit in associative memory, reflecting the difficulties they have in binding features of episodes into cohesive entities and retrieving these bindings. Here, we evaluate the degree to which this deficit may be mediated by sensory loss associated with increased age. In 2 experiments, young adults studied word pairs that were degraded at encoding either visually (Experiment 1) or auditorily (Experiment 2). We then tested their memory for both the component words and the associations with recognition tests. For both experiments, young adults under nondegraded conditions showed an advantage in associative over item memory, relative to a group of older adults. In contrast, under perceptually degraded conditions younger adults performed similarly to the older adults who were tested under nondegraded conditions. More specifically, under perceptual degradation, young adults' associative memory declined and their component memory improved somewhat, resulting in an associative deficit, similar to that shown by older adults. This evidence is consistent with a sensory acuity decline in old age being one mediator in the associative deficit of older adults. These results broaden our understanding of age-related memory changes and how sensory and cognitive processes interact to shape these changes. The theoretical implications of these results are discussed with respect to mechanisms underlying age-related changes in episodic memory and resource tradeoffs in the encoding of component and associative memory.

Degraded conditions: Confounds in the study of decision making

I raise a consideration complementary to those raised in the target article. Many of the most widely cited studies on decision making involve introspection in degraded conditions, namely, conditions in which agents have no reason for the decisions they reach. But the fact that confabulation occurs in degraded conditions does not impugn the reliability of introspection in non-degraded conditions, that is, in cases in which a subject actually does make a choice for a reason.

Photoacoustic spectroscopy as an approach to assess chemical modifications in edible oils

Photoacoustic spectroscopy was used to obtain optical properties of edible soybean, canola and olive oils as well to evaluate the oil modifications induced by thermal treatment. The normalized photoacoustic signal intensity and its phase were independently measured as a function of wavelength of the radiation source. The oil samples were heated up to the smoke point and then for additional 30 min in order to degrade them. After, the oil samples were cooled down and photoacoustic measurements were conducted in order to obtain the absorption spectra of samples at both degraded and non-degraded conditions. Comparisons between the two conditions indicate that the degraded oil samples exhibited widening of the absorption bands in ultraviolet region of the spectra, relative to the respective non-degraded sample. Also, the peaks of those absorption bands presented a red shift.

Photoacoustic Spectroscopy as an Approach to Assess Chemical Modifications in Edible Oils

Photoacoustic spectroscopy was used to obtain optical properties of edible soybean, canola and olive oils as well to evaluate the oil modifications induced by thermal treatment. The normalized photoacoustic signal intensity and its phase were independently measured as a function of wavelength of the radiation source. The oil samples were heated up to the smoke point and then for additional 30 min in order to degrade them. After, the oil samples were cooled down and photoacoustic measurements were conducted in order to obtain the absorption spectra of samples at both degraded and non-degraded conditions. Comparisons between the two conditions indicate that the degraded oil samples exhibited widening of the absorption bands in ultraviolet region of the spectra, relative to the respective non-degraded sample. Also, the peaks of those absorption bands presented a red shift.

Impact of alpine meadow degradation on soil hydraulic properties over the Qinghai-Tibetan Plateau

Summary Alpine meadow soil is an important ecosystem component of the Qinghai-Tibetan Plateau. However, the alpine meadow soil is undergoing serious degradation mainly due to global climate change, overgrazing, human activities and rodents. In this paper, spatial sequencing was chosen over time succession sequencing to study the changes of soil hydraulic properties under different degrees of alpine meadow degradation. Soil saturated hydraulic conductivity (Ks) and Gardner α both at the surface and at 40–50 cm depth were investigated in the field using tension infiltrometers. Soil physical and chemical properties, together with the root index at 0–10 cm and 40–50 cm soil layer depths were also analyzed. Pearson correlations were adopted to study the relationships among the investigated factors and principal component analysis was performed to identify the dominant factor. Results show that with increasing degree of degradation, soil sand content increased while soil Ks and Gardner α as well as soil clay content, soil porosity decreased in the 0–10 cm soil layers, and organic matter and root gravimetric density decreased in both the 0–10 cm and 40–50 cm soil layers. However, soil moisture showed no significant changes with increasing degradation. With decreasing pressure head, soil unsaturated hydraulic conductivity reduced more slowly under degraded conditions than non-degraded conditions. Soil Ks and Gardner α were significantly correlated (P = 0.01) with bulk density, soil porosity, soil organic matter and root gravimetric density. Among these, soil porosity is the dominant factor explaining about 90% of the variability in total infiltration flow. Under non-degraded conditions, the infiltration flow principally depended on the presence of macropores. With increasing degree of degradation, soil macropores quickly changed to mesopores or micropores. The proportion of total infiltration flow through macropores and mesopores significantly decreased with the most substantial decrease observed for the macropores in the 0–10 cm soil layer. The substantial decrease of macropores caused a cut in soil moisture and hydraulic conductivity. This study improves the understanding and prediction of alpine meadow soil and ecosystem changes and provides guidelines for improving water flow modeling under the background of global climate change over the Qinghai-Tibetan Plateau and similar regions.

Deteriorating Environmental Resources and Primary School Educational Attainment in the Rural South Pare Highlands, Tanzania

We assess whether school attendance and progress of children in rural primary schools, with respect to their gender, is inversely affected by deteriorating environmental resources. We distinguished three types of areas, namely, severely-degraded, medium-degraded and non-degraded environmental conditions. Our findings, among others, show that there were other factors like school crowdedness, illness, bad weather, school absenteeism due to petty trading and/or informal casual labour, and poor quality of some primary schools that significantly affected the probability of school attainment for the schoolchildren apart from the environmental degradation situations. Environmental degradation, in all estimates except for the schoolgirls in severely-degraded environment, did not have a significant impact. The policy makers therefore, in their attempt to improve educational attainment and human capital formation at primary level should, as well, focus on these other relevant factors excluded from our model. Moreover, the non-government sector may also be enticed into investing in education through attractive fiscal incentives.

Sustained-release of flutamide from radiation-crosslinked poly(4-acryloyl morpholine-acrylic acid) hydrogels

The present work reports the effect of radiation cross-linking on aqueous solution of 4-acryloyl morpholine (ACMO)/acrylic acid (AA) in the presence of flutamide (FLT), an anticancer drug. Use of a γ-irradiation process within 5 kGy provided an insoluble hydrogel. Ultraviolet-visible absorption, fluorescence spectroscopy, and Fourier transform infrared spectroscopy were employed to study the complex formation of FLT with ACMO and AA. The ability of the prepared ACMO/AA-based hydrogels to be used as drug carriers for anticancer-specific drug delivery system was estimated using FLT as a model drug. In vitro drug release studies in a pH 7 buffer solution show that 20%–30% of the FLT was continuously released from the FLT-incorporated ACMO/AA hydrogel within 1 day, followed by a gradual release upon 7 days under in vitro non-degradation hydrogel conditions. The recognition affinity of the ACMO/AA/FLT hydrogel is increased when synthesized in a high-concentration template solution. Open image in new window

Drug eluting stents based on Poly(ethylene carbonate): Optimization of the stent coating process

First generation drug eluting stents (DES) show a fivefold higher risk of late stent thrombosis compared to bare metal stents. Therefore, new biodegradable and biocompatible polymers for stent coating are needed to reduce late stent thrombosis. In this study, a reproducible spray-coating process for stents coated with Poly(ethylene carbonate), PEC, and Paclitaxel was investigated. PEC is a biocompatible, thermoelastic polymer of high molecular weight. The surface degradation of PEC is triggered by superoxide anions produced by polymorphonuclear leukocytes and macrophages during inflammatory processes. Stents with different drug loading were reproducibly produced by a spray-coating apparatus. Confocal laser scanning micrographs of fluorescent dye loaded stents were made to investigate the film homogeneity. The abluminal stent site was loaded more than the luminal site, which is superior for DES. The deposition of the layers was confirmed by TOF-SIMS investigations. Referring to the stent surface, the drug loading is 0.32μg (±0.05) (once coated), 0.53μg (±0.11) (twice coated), or 0.73μg (±0.06) (three times coated) Paclitaxel per mm2 stent surface. The in vitro release mechanism during non-degradation conditions can be explained by diffusion-controlled drug release slightly influenced by swelling of PEC, revealing that 100% of the loaded Paclitaxel will be released via diffusion within 2months. So, the in vivo release kinetic is a combination of diffusion-controlled drug release and degradation-controlled drug release depending on the presence or absence of superoxide anions and accordingly depending on the presence or absence of macrophages. We conclude that the specific release kinetics of PEC, its biocompatibility, and the favorable mechanical properties will be beneficial for a next generation drug eluting stent meriting further investigations under in vivo conditions.

Biocompatibility of poly(ethylene glycol)‐based hydrogels in the brain: An analysis of the glial response across space and time

Poly(ethylene glycol) or PEG-based hydrogels provide a useful methodology for tissue engineering and the controlled-release of drugs within the central nervous system (CNS). To be successful, the local neuroinflammatory response to an implant must be well understood. Toward this end, the focus was to examine the localized recruitment and activation of microglia and astrocytes following implantation of PEG-based hydrogels in the brain. Because they are of clinical relevance and may impact brain tissue differently, hydrogels with different mass loss profiles were examined. At all time points, a needle penetration in sham animals evoked a greater astrocytic response than hydrogel conditions. The astrocyte response that ensued varied with degradation rate. An attenuated response was present in more slowly degrading and nondegrading conditions. Relative to sham, hydrogel conditions attenuated the acute microglial response during the week after implant. By 56 days, microglial levels in shams decreased below the observed response in slowly degrading and nondegradable gels, which remained constant overtime. Although the inflammatory response to PEG-based hydrogels was complex depending on degradation rates, the magnitude of the acute microglia response and the long-term astrocyte response were attenuated suggesting the use of these materials for drug and cell delivery to the CNS.

Toward a full characterization of native starch: Separation and detection by size-exclusion chromatography

The structure of starch molecules is relevant to nutrition and industrial applications. Size-exclusion chromatography (SEC, also known as GPC) of native starch generally suffers non-satisfactory repeatability and reproducibility of the dissolution and separation. This work combines two polar organic solvents: dimethylsulfoxide for complete dissolution and dimethylacetamide to limit shear degradation. The separation is as repeatable as that of polystyrene standards performing dissolution and separation at 80 °C. Successful covalent-labeling on the glucose unit is claimed to be published here for the first time in non-degradative conditions and allows the use of UV detector with significantly higher sensitivity than with a refractometer.

Coping with Polychlorinated Biphenyl (PCB) Toxicity: Physiological and Genome-Wide Responses of Burkholderia xenovorans LB400 to PCB-Mediated Stress

The biodegradation of polychlorinated biphenyls (PCBs) relies on the ability of aerobic microorganisms such as Burkholderia xenovorans sp. LB400 to tolerate two potential modes of toxicity presented by PCB degradation: passive toxicity, as hydrophobic PCBs potentially disrupt membrane and protein function, and degradation-dependent toxicity from intermediates of incomplete degradation. We monitored the physiological characteristics and genome-wide expression patterns of LB400 in response to the presence of Aroclor 1242 (500 ppm) under low expression of the structural biphenyl pathway (succinate and benzoate growth) and under induction by biphenyl. We found no inhibition of growth or change in fatty acid profile due to PCBs under nondegrading conditions. Moreover, we observed no differential gene expression due to PCBs themselves. However, PCBs did have a slight effect on the biosurface area of LB400 cells and caused slight membrane separation. Upon activation of the biphenyl pathway, we found growth inhibition from PCBs beginning after exponential-phase growth suggestive of the accumulation of toxic compounds. Genome-wide expression profiling revealed 47 differentially expressed genes (0.56% of all genes) under these conditions. The biphenyl and catechol pathways were induced as expected, but the quinoprotein methanol metabolic pathway and a putative chloroacetaldehyde dehydrogenase were also highly expressed. As the latter protein is essential to conversion of toxic metabolites in dichloroethane degradation, it may play a similar role in the degradation of chlorinated aliphatic compounds resulting from PCB degradation.

Controlled release of paclitaxel from photocrosslinked chitosan hydrogels and its subsequent effect on subcutaneous tumor growth in mice

A photocrosslinkable chitosan (Az–CH–LA) aqueous solution containing paclitaxel resulted in an insoluble hydrogel within 30 s of ultrtaviolet light (UV)-irradiation. About 35–40% of the paclitaxel was released from the paclitaxel-incorporated chitosan hydrogel into phosphate buffered saline (PBS) within 1 day, after which gradual release occurred during 3 days under in vitro non-degradation conditions of the hydrogel. The paclitaxel remaining in the chitosan hydrogel retained its biological activity in vitro for at least 21 days, and was released from the chitosan hydrogel in vivo upon degradation of the hydrogel. The paclitaxel-incorporated Az–CH–LA hydrogel inhibited the growth of subcutaneously induced tumors with Lewis lung cancer (3LL) cells more effectively than those treated with only Az–CH–LA, only paclitaxel, and a non-treated group (control) for at least 11 days. Furthermore, paclitaxel-incorporated chitosan hydrogel markedly reduced the number of CD34-positive vessels in subcutaneous 3LL tumors, indicating a strong inhibition of angiogenesis. These results suggested that application of paclitaxel-incorporated Az–CH–LA hydrogel has an inhibitory activity on angiogenesis and tumor growth.

Photocrosslinkable chitosan hydrogel containing fibroblast growth factor-2 stimulates wound healing in healing-impaired db/db mice

Application of ultraviolet light (UV-) irradiation to a photocrosslinkable chitosan (Az-CH-LA) aqueous solution including fibroblast growth factor-2 (FGF-2) resulted within 30 s in an insoluble, flexible hydrogel. About 20% of the FGF-2 molecules were released from the FGF-2-incorporated chitosan hydrogel into phosphate buffered saline (PBS) within 1 day, after which no further significant release occurred under in vitro non-degradation conditions of the hydrogel. The FGF-2 molecules retained in the chitosan hydrogel remained biologically active, and were released from the chitosan hydrogel upon the in vivo biodegradation of the hydrogel. In order to evaluate its accelerating effect on wound healing, full thickness skin incisions were made on the back of healing-impaired diabetic ( db/db) mice and their normal ( db/+) littermates. Application of the chitosan hydrogel significantly induced wound contraction and accelerated wound closure in both db/db and db/+ mice. However, the addition of FGF-2 in the chitosan hydrogel further accelerated wound closure in db/db mice, although not in db/+ mice. Histological examination also has demonstrated an advanced granulation tissue formation, capillary formation and epithelialization in wounds treated with FGF-2-incorporated chitosan hydrogels in db/db mice.

Controlled release of fibroblast growth factors and heparin from photocrosslinked chitosan hydrogels and subsequent effect on in vivo vascularization.

Application of ultraviolet (UV) irradiation to a photocrosslinkable chitosan (Az-CH-LA) aqueous solution resulted within 10 s in an insoluble, flexible hydrogel. A low molecular weight acidic molecule like trypan blue and various high molecular weight molecules such as bovine serum albumin (BSA), heparin and protamine were all retained within the hydrogel, while a low molecular weight basic molecule like toluidine blue was rapidly released from the hydrogel. In the present work, we examined the retaining capability of the chitosan hydrogel for growth factors and controlled release of growth factors from the chitosan hydrogel in vitro and in vivo. Fibroblast growth factor-1 (FGF-1), fibroblast growth factor-2 (FGF-2), vascular endothelial growth factor(165) (VEGF(165)), heparin-binding epidermal growth factor (HB-EGF) in phosphate buffered saline (PBS) were mixed with Az-CH-LA aqueous solution to form growth factor-incorporated chitosan hydrogels. About 10-25% of the growth factor was released from a growth factor-incorporated chitosan hydrogel into PBS within the first day, after which no further substantial release took place. The growth factors interacted with Az-CH-LA molecules poly-ion complexation, and probably were unable to be released after the first day under the in vitro nondegradation conditions of the hydrogel. Although the FGF-1, FGF-2, and VEGF(165)-incorporated chitosan hydrogels on a culture plate significantly stimulated HUVEC growth, the stimulating activity of the growth factor-incorporated chitosan hydrogel was completely cancelled out by washing the hydrogel with PBS solution for 3 days or more. The stimulating activity on the HUVEC growth were however highly recovered by treating the washed growth factor-incorporated chitosan hydrogel during 7 days with chitinase and chitosanase to partly degrade the hydrogel, strongly suggesting that the growth factors within the hydrogel retained their biologically active forms. The chitosan hydrogel (100 microl) when implanted into the back of a mouse was biodegraded in about 10-14 days. When FGF-1- and FGF-2-incorporated chitosan hydrogels were subcutaneously implanted into the back of a mouse, significant neovascularization was induced near the implanted site of the FGF-1- and FGF-2-incorporated chitosan hydrogels. Furthermore, addition of heparin with either FGF-1 or FGF-2 into the hydrogel resulted in a significantly enhanced and prolonged vascularization effect. These results indicate that the controlled release of biologically active FGF-1 and FGF-2 with heparin is caused by biodegradation of the chitosan hydrogel, and subsequent induction of vascularization.

An estuarine benthic index of biotic integrity for the Mid-Atlantic region of the United States. II. Index development

A benthic index of biotic integrity was developed for use in estuaries of the mid-Atlantic region of the United States (Delaware Bay estuary through Albemarle-Pamlico Sound). The index was developed for the Mid-Atlantic Integrated Assessment Program (MAIA) of the U.S. Environmental Protection Agency using procedures similar to those applied previously in Chesapeake Bay and southeastern estuaries, and was based on sampling in July through early October. Data from seven federal and state sampling programs were used to categorize sites as degraded or non-degraded based on dissolved oxygen, sediment contaminant, and sediment toxicity criteria. Various metrics of benthic community structure and function that distinguished between degraded and reference (non-degraded) sites were selected for each of five major habitat types defined by classification analysis of assemblages. Each metric was scored according to thresh- olds established on the distribution of values at reference sites, so that sites with low scoring metrics would be expected to show signs of degradation. For each habitat, metrics that correctly classified at least 50% of the degraded sites in the calibration data set were selected whenever possible to derive the index. The final index integrated the average score of the combination of metrics that performed best according to several criteria. Selected metrics included measures of productivity (abundance), diversity (number of taxa, Shannon-Wiener diversity, percent dominance), species composition and life history (percent abundance of pollution-indicative taxa, percent abundance of pollution-sensitive taxa, percent abundance of Bivalvia, Tanypodinae-Chironomidae abundance ratio), and trophic composition (percent abundance of deep-deposit feeders). The index correctly classified 82% of all sites in an independent data set. Classification efficiencies of sites were higher in the mesohaline and polyhaline habitats (81-92%) than in the oligohaline (71%) and the tidal freshwater (61%). Although application of the index to low salinity habitats should be done with caution, the MAIA index appeared to be quite reliable with a high likelihood of correctly identifying both degraded and non-degraded conditions. The index is expected to be of great utility in regional assessments as a tool for evaluating the integrity of benthic assemblages and tracking their condition over time.

Controlled release of growth factors based on biodegradation of gelatin hydrogel

To develop a carrier for the controlled release of biologically-active growth factors, biodegradable hydrogels were prepared through glutaraldehyde cross-linking of gelatin with isoelectric points (IEP) of 5.0 and 9.0, i.e. 'acidic' and 'basic' gelatins, respectively. Radioiodinated growth factors were used to investigate their sorption and desorption from the hydrogel of both types of gelatin. Basic fibroblast growth factor (bFGF) and transforming growth factor-β1 (TGF-β1) were well sorbed with time to the acidic gelatin hydrogel, while less sorption was observed for the basic gelatin hydrogel. This could be explained in terms of the electrostatic interaction between the growth factors and the acidic gelatin. However, bone morphogenetic protein-2 (BMP-2) and vascular endothelial growth factor (VEGF), though their IEPs are higher than 7.0, were sorbed to the acidic gelatin hydrogel to a smaller extent than the two other growth factors. Under in vitro non-degradation conditions, approximately 20% of the incorporated bFGF and TGF-β1 was desorbed from the hydrogels within the initial 40 min, followed by no further substantial desorption, whereas large initial desorption was observed for BMP-2 and VEGF. When implanted in the back subcutis of mice, gelatin hydrogels were degraded over time. Each growth factor was retained in vivo being incorporated in the acidic gelatin hydrogel: the smaller the in vitro desorption amount from the hydrogel, the longer the in vivo retention time. The in vivo profile of bFGF and TGF-β1 retention was in good accordance with that of the hydrogel. These findings indicate that the growth factor immobilized to the acidic gelatin hydrogel through ionic interaction was released in vivo as a result of hydrogel degradation.

Surfactant-Free Preparation of Biodegradable Hydrogel Microspheres for Protein Release

The preparation of biodegradable hydrogel microspheres in the absence of surfactants was carried out by a two-step procedure which involved the formation of non-crosslinked microspheres from gelatin based on its inherent gelation nature at low temperatures and the subsequent glutaraldehyde (GA) crosslinking. The size of the microspheres was controlled in the range of 3 to 100 μm by changing the concentration of gelatin or GA, the emulsification method, and the crosslinking time. Neutral aqueous solutions of proteins with different isoelectric points (IEPs) and molecular weights (Mws) were infused into freeze-dried hydrogel microspheres to produce protein-incorporated gelatin microspheres. In vitro protein release from the microspheres depended on the protein's IEP but not on the Mw. The incorporated basic proteins with IEPs > 7.0 were released initially from the acidic gelatin microspheres, followed by no substantial release, whereas a larger initial release of the incorporated acidic proteins with IEPs < 7.0 was observed. The basic gelatin microspheres exhibited an opposite relationship between proteins IEP and protein release. Noncharged dextran rapidly diffused out of acidic gelatin microspheres, irrespective of the Mw. These findings indicate that an ionic interaction with gelatin constituted hydrogel microspheres prevented oppositely charged protein from being released from gelatin under in vitro non-degradation conditions.