[Costicartilage analysis inspection technology in the application of forensic medicine]

The traditional costicartilage analysis inspection is limited to morphological inspection. In recent years, with the development of forensic radiology and molecular genetics, the costicartilage analysis inspection technology has been further enriched and developed. At present, the costicartilage analysis inspection technology have been able to be used in the practice of forensic medicine. This paper reviews the research advances about the costicartilage analysis inspection technology in the identification of human gender, age and so on in order to provide the references for forensic appraisers.

Comparative study of the angle-resolved backscattering properties of collagen fibers in bovine tendon and cartilage

In a biological tissue, light scattering is based on the size and type of scatterers seen as refractive index variations that describe the optical properties shown. In this paper, we have implemented the variable incidence angle technique of multiple angle of illumination experiment on tendon and cartilage samples whose dominant constituents are genetically different types of collagen fibers, type I and type II, respectively. It is found that tendon displays a much greater angular anisotropy in its optical backscattering coefficient than the healthy cartilage. We propose that this is due to a more uniform distribution of fine fibrils than is found in tendon. Rayleigh-Gans approximation is used to give qualitative support to this idea.

1H and 13C NMR studies of glycine in anisotropic media: double-quantum transitions and the effects of chiral interactions

The (1)H NMR spectrum of glycine in stretched gelatin gel and in cromolyn liquid crystal displays a well-resolved doublet due to (1)H-(1)H dipolar interaction. Multiple spectra were obtained within a wide range of offset frequencies of partially saturating radio-frequency (RF) radiation to generate steady-state irradiation envelopes or z-spectra of glycine. Maximal suppression of the doublet occurred when the irradiation was applied exactly at the centre frequency, between the two glycine peaks. This phenomenon is due to double-quantum transitions and is similar to our previous work on quadrupolar nuclei (2)H (HDO) and (23)Na(+). When the (13)C isotopomer glycine-2-(13)C was used, the same effect was found in twice, split by (1)J(CH)+2D(CH). Additional signals in (1)H and (13)C NMR due to prochiral-chiral interactions were found when glycine-2-(13)C was dissolved in chiral anisotropic gelatin and κ-carrageenan gels. The NMR spectra were successfully simulated assuming a (2)J(HH) coupling constant of -16.5Hz and two distinct dipolar coupling constants for the -(13)CH(2)- group (D(C,HA), and D(C,HB)).

Anomalous NMR relaxation in cartilage matrix components and native cartilage: fractional-order models

We present a fractional-order extension of the Bloch equations to describe anomalous NMR relaxation phenomena (T(1) and T(2)). The model has solutions in the form of Mittag-Leffler and stretched exponential functions that generalize conventional exponential relaxation. Such functions have been shown by others to be useful for describing dielectric and viscoelastic relaxation in complex, heterogeneous materials. Here, we apply these fractional-order T(1) and T(2) relaxation models to experiments performed at 9.4 and 11.7 Tesla on type I collagen gels, chondroitin sulfate mixtures, and to bovine nasal cartilage (BNC), a largely isotropic and homogeneous form of cartilage. The results show that the fractional-order analysis captures important features of NMR relaxation that are typically described by multi-exponential decay models. We find that the T(2) relaxation of BNC can be described in a unique way by a single fractional-order parameter (α), in contrast to the lack of uniqueness of multi-exponential fits in the realistic setting of a finite signal-to-noise ratio. No anomalous behavior of T(1) was observed in BNC. In the single-component gels, for T(2) measurements, increasing the concentration of the largest components of cartilage matrix, collagen and chondroitin sulfate, results in a decrease in α, reflecting a more restricted aqueous environment. The quality of the curve fits obtained using Mittag-Leffler and stretched exponential functions are in some cases superior to those obtained using mono- and bi-exponential models. In both gels and BNC, α appears to account for micro-structural complexity in the setting of an altered distribution of relaxation times. This work suggests the utility of fractional-order models to describe T(2) NMR relaxation processes in biological tissues.

Chemical changes demonstrated in cartilage by synchrotron infrared microspectroscopy in an antibody-induced murine model of rheumatoid arthritis

Collagen antibody-induced arthritis develops in mice following passive transfer of monoclonal antibodies (mAbs) to type II collagen (CII) and is attributed to effects of proinflammatory immune complexes, but transferred mAbs may react directly and damagingly with CII. To determine whether such mAbs cause cartilage damage in vivo in the absence of inflammation, mice lacking complement factor 5 that do not develop joint inflammation were injected intravenously with two arthritogenic mAbs to CII, M2139 and CIIC1. Paws were collected at day 3, decalcified, paraffin embedded, and 5-μm sections were examined using standard histology and synchrotron Fourier-transform infrared microspectroscopy (FTIRM). None of the mice injected with mAb showed visual or histological evidence of inflammation but there were histological changes in the articular cartilage including loss of proteoglycan and altered chondrocyte morphology. Findings using FTIRM at high lateral resolution revealed loss of collagen and the appearance of a new peak at 1635 cm(-1) at the surface of the cartilage interpreted as cellular activation. Thus, we demonstrate the utility of synchrotron FTIRM for examining chemical changes in diseased cartilage at the microscopic level and establish that arthritogenic mAbs to CII do cause cartilage damage in vivo in the absence of inflammation.

[Effect of acupuncture on expression of matrix metalloproteinase and tissue inhibitor in cartilage of rats with knee osteoarthritis]

OBJECTIVE

To explore the curative mechanism of acupuncture treatment on osteoarthritis (OA).

METHODS

Forty cases of female SD rats were randomly divided into a normal group, a model group, an acupuncture group and a medication group, 10 cases in each group. OA animal model was established by using the method of heel tendon resection for unilateral hind limb. The acupuncture group was treated with electroacupuncture at "Xiqian"(ST 35) and "Housanli"(ST 36), and the medication group with inunction of Diclofenac cream, and the normal group and the model group without any treatment. The expression of matrix metalloproteinase-1, 3 (MMP-1, MMP-3) and tissue inhibitor of metalloproteinase-1 (TIMP-1) in the cartilage were observed by immunohistochemistry.

RESULTS

There were significant differences among four groups. The expressions of MMP-1, MMP-3 and TIMP-1 in the model, acupuncture and medication groups were all significantly stronger than those in the normal group (all P < 0.01). The expressions of MMP-1 and MMP-3 in the acupuncture and medication groups were down regulated and TIMP-1 expression up-regulated with significant differences as compared with the model group (all P < 0.01), and the expressions of MMP-1 and MMP-3 in acupuncture group were significantly lower, while TIMP-1 expression significantly higher than that in the medication group (all P < 0.01).

CONCLUSION

Acupuncture can down-regulate the expression of MMP-1 and MMP-3 and up-regulate the expression of TIMP1, which is superior to that of Diclofenac cream, showing that acupuncture has a certain protective effect on cartilage from OA.

Multifunctional hybrid three-dimensionally woven scaffolds for cartilage tissue engineering

The successful replacement of large-scale cartilage defects or osteoarthritic lesions using tissue-engineering approaches will likely require composite biomaterial scaffolds that have biomimetic mechanical properties and can provide cell-instructive cues to control the growth and differentiation of embedded stem or progenitor cells. This study describes a novel method of constructing multifunctional scaffolds for cartilage tissue engineering that can provide both mechanical support and biological stimulation to seeded progenitor cells. 3-D woven PCL scaffolds were infiltrated with a slurry of homogenized CDM of porcine origin, seeded with human ASCs, and cultured for up to 42 d under standard growth conditions. These constructs were compared to scaffolds derived solely from CDM as well as 3-D woven PCL fabric without CDM. While all scaffolds promoted a chondrogenic phenotype of the ASCs, CDM scaffolds showed low compressive and shear moduli and contracted significantly during culture. Fiber-reinforced CDM scaffolds and 3-D woven PCL scaffolds maintained their mechanical properties throughout the culture period, while supporting the accumulation of a cartilaginous extracellular matrix. These findings show that fiber-reinforced hybrid scaffolds can be produced with biomimetic mechanical properties as well as the ability to promote ASC differentiation and chondrogenesis in vitro.

[Extraction and antihypertensive activity analysis of chondroitin sulfate from different animals]

OBJECTIVE

Chondroitin Sulfate (CS) from different animals were extracted, which antihypertensive activities were compared.

METHODS

CS from the bovine and chicken cartilages were extracted by diluted alkali-enzyme hydrolysis method, with removed free protein by Sevag method, separated and purified by quaternary ammonium complex. Their antihypertensive activities were tested by the modal of SPF rat.

RESULTS

The extracted CS didn't have peptide, amino acid or other acid mucopolysaccharides determined by electrophoresis and chromatography, the results of IR was consisted with that of chondroitin sulfate supplied by Sigma Both BCCS and CCCS indicated the antihypertensive activities in the low dosage. Besides, BCCS had faster efficacy but shorter duration than that of CCCS.

CONCLUSION

Both BCCS and CCCS had high purity. Animal experiments showed that BCCS and CCCS have the effect of the antihypertensive, which activity of CCCS was more significant than that of BCCS.

Transmission electron microscopy of cartilage and bone

This review of cartilage microscopy is restricted to a brief description of the major molecular components in cartilage and bone and an in-depth discussion of methods for the preparation of these tissues for examination by transmission electron microscopy. Included within are simple methods for the isolation of cartilage-specific macromolecules, methods for immunoidentification of tissue components, bone decalcification protocols, and fixative recipes designed to stabilize cells and proteoglycan within the cartilage matrix. A discussion of cartilage prepared by high-pressure freezing (HPF)/freeze substitution (FS) is also presented.

SHP-1, a novel peptide isolated from seahorse inhibits collagen release through the suppression of collagenases 1 and 3, nitric oxide products regulated by NF-kappaB/p38 kinase

Considerable efforts have been taken to identify natural peptides as potential bioactive substances. In this study, novel peptide (SHP-1) derived from seahorse (Hippocampus, Syngnathidae) hydrolysate was explored for its inhibitory effects on collagen release in arthritis with the investigation of its underlying mechanism of action. The efficacy of SHP-1 was determined on cartilage protective effects such as inhibition of collagen and GAG release. SHP-1 was able to suppress not only the expression of collagenases 1 and 3, but also the production of NO via down-regulation of iNOS. However, it presented an irrelevant effect on the level of GAG release in chondrocytic and osteoblastic cells. Inhibition of collagen release by SHP-1 is associated with restraining the phosphorylation of NF-kappaB and p38 kinase cascade. Therefore, it could be suggested that SHP-1 has a potential to be used in arthritis treatment.

Stable-isotope comparisons between embryos and mothers of a placentatrophic shark species

Stable nitrogen (delta(15)N) and carbon (delta(13)C) isotopes of Atlantic sharpnose shark Rhizoprionodon terraenovae embryos and mothers were analysed. Embryos were generally enriched in (15)N in all studied tissue relative to their mothers' tissue, with mean differences between mother and embryo delta(15)N (i.e. Deltadelta(15)N) being 1.4 per thousand for muscle, 1.7 per thousand for liver and 1.1 per thousand for cartilage. Embryo muscle and liver were enriched in (13)C (both Deltadelta(13)C means = 1.5 per thousand) and embryo cartilage was depleted (Deltadelta(13)C mean = -1.01 per thousand) relative to corresponding maternal tissues. While differences in delta(15)N and delta(13)C between mothers and their embryos were significant, muscle delta(15)N values indicated embryos to be within the range of values expected if they occupied a similar trophic position as their respective mothers. Positive linear relationships existed between embryo total length (L(T)) and Deltadelta(15)N for muscle and liver and embryo L(T) and Deltadelta(13)C for muscle, with those associations possibly resulting from physiological differences between smaller and larger embryos or differences associated with the known embryonic nutrition shift (yolk feeding to placental feeding) that occurs during the gestation of this placentatrophic species. Together these results suggest that at birth, the delta(15)N and delta(13)C values of R. terraenovae are likely higher than somewhat older neonates whose postpartum feeding habits have restructured their isotope profiles to reflect their postembryonic diet.

Classification of degraded cartilage through multiparametric MRI analysis

MRI analysis of cartilage matrix may play an important role in early detection and development of therapeutic protocols for degenerative joint disease. Correlations between MRI parameters and matrix integrity have been established in many studies, but the substantial overlap in values observed for normal and for degraded cartilage greatly limits the specificity of these analyses. We implemented established multiparametric analysis methods to define data clusters corresponding to control and degraded bovine nasal cartilage in two-, three-, and four-dimensional parameter spaces, and applied these results to discriminant analysis of a validation data set. Analyses were performed using the parameters (T(1), T(2), k(m), ADC), where k(m) is the magnetization transfer rate and ADC is the apparent diffusion coefficient. Results were compared to univariate analyses. Multiparametric k-means clustering led to no improvement over univariate analyses, with a maximum sensitivity and specificity in the range of 60-70% for the detection of degradation using T(1), and in the range of 80% sensitivity but only 36% specificity using the parameter pair (T(1), k(m)). In contrast, model-based analysis using more general Gaussian clusters resulted in markedly improved classification, with sensitivity and specificity reaching levels of 80-90% using the pair (T(1), k(m)). Finally, a fuzzy clustering technique was implemented which may be still more appropriate to the continuum of degradation seen in degenerative cartilage disease. In view of its success in identifying mild cartilage degradation, the formal multiparametric approach implemented here may be applicable to the nondestructive evaluation of other biomaterials using MRI.

The cytoskeleton of chondrocytes of Sepia officinalis (Mollusca, Cephalopoda): an immunocytochemical study

Our previous electron microscope study showed that chondrocytes from cephalopod cartilage possess a highly developed cytoskeleton and numerous cytoplasmic processes that ramify extensively through the tissue. We have now carried out a light microscope immunocytochemical study of chondrocytes from the orbital cartilage of Sepia officinalis to obtain indications as to the nature of the cytoskeletal components. We found clear positivity to antibodies against mammalian tubulin, vimentin, GFAP, and actin, but not keratin. The simultaneous presence of several cytoskeletal components is consistent with the hypothesis that cephalopod chondrocytes have the characteristics of both chondrocytes and osteocytes of vertebrates, which endow the tissue as a whole with some of the properties of vertebrate bone. We confirm, therefore, the presence in molluscs of the ubiquitous cytoskeletal proteins of metazoan cells that have remained highly conserved throughout phylogenetic evolution.

The bioaccumulation of fluoride ion (F(-)) in Siberian sturgeon (Acipenser baerii) under laboratory conditions

A 90-d growth trial was conducted to determine the accumulation of fluoride ions (F(-)) in juvenile Siberian sturgeon (Acipenser baerii). Fish were exposed to nominal F(-) concentrations of 4, 10, 25, 62.5 mg L(-1) (added as NaF), along with a control group. Fish growth was determined and F(-) concentrations in bone, cartilage, skin, gill, muscle, liver, gut and pylorus were analyzed by fluoride specific electrode method. Fish growth was inhibited for groups exposed to 10, 25, and 62.5 mg F(-) L(-1) compared to the control group. Significant increases in F(-) concentrations were observed in bone, cartilage, skin and gill of Siberian sturgeon exposed to 4 mg F(-) L(-1). The highest F(-) concentration was in bone (3204.4 mg kg(-1), dry weight), followed by cartilage (1401.2 mg kg(-1)), gill (389.4 mg kg(-1)), skin (100.1 mg kg(-1)). Muscle, liver, gut and pylorus did not show increasing accumulation with increasing F(-) levels in the water, but liver, gut, pylorus accumulated higher F(-) concentration compared to muscle. It is summarized that F(-) accumulates mainly in bone and cartilage in Siberian sturgeon, with 10 mg F(-) L(-1) in water harmful to growth. Even 4 mg F(-) L(-1) may be harmful to Siberian sturgeon growth during a long-term waterborne exposure.

[The effects of microenvironment on tissue-engineered osteochondral composite]

It is currently reported that extracellular matrix, biological scaffolds, conditions of stress, nutrients and metabolic waste play very important roles in tissue-engineered osteochondral composite. In this paper, we have made a review of their effects on such composite.

Alcian blue/alizarin red staining of cartilage and bone of short-tailed fruit bat (Carollia perspicillata)

This protocol is used to stain embryo skeleton with alcian blue and alizarin red at later stages of development, when there is significant replacement of the cartilaginous early skeleton with ossified bone. It has been used with good results on the short-tailed fruit bat Carollia perspicillata and other bat species from CS 20 through neonatal stages.

[Morphological characteristics of bone tissue regeneration process in young and old animals]

The paper describes the results of the morphological study of the bone tissue repair process in young and old animals on the model of bone skeleton damage. The defect of the cortical bone was reached by means of bringing in a teflon fistula to make a tunnel surrounded by bone tissue, providing condition for studying the character of bone marrow elements migration to the created hollow space. Repair processes in the bone tissue of old animals were found to elapse much slower than in young ones. However, administration of embryonic cartilaginous and bone tissue extracts into the area of bone defect in old animals facilitated the process of bone tissue repair. The obtained results may serve as a prerequisite for the development of methods for optimization of rehabilitation in old and senile patients with fractures of cortical bones.

Lifetime accumulation of (137)Cs and (40)K in the ribs and sternum of an Austrian "mountain pasture" cow

The accumulation of natural and artificial radionuclides in humans and domestic animals is of interest in estimating effective doses of exposed humans and to decide whether animal products can be used for nutrition of the population. In this paper we present an investigation of the (137)Cs- and (40)K-activity levels of the ribs and sternum of a "mountain pasture" cow, born in a highly contaminated region of Styria, Austria, at the time of the radioactive fallout following the Chernobyl accident. This is the first systematic investigation of the variation in activity levels of a contaminated animal. The International Commission on Radiological Protection (ICRP) assumes that cesium and potassium are homogenously distributed throughout the whole body of an organism. However, the presented results show that there is a non-uniform distribution of (137)Cs and (40)K in different skeletal bones and their adherent tissues of a dairy cattle. We found that activity concentrations of (137)Cs and (40)K varied up to a factor 2.5 in different components of the ribs. The minimum values of (137)Cs and (40)K in the ribs were 29.9 and 21Bqkg(-1) fresh mass for trabecular bone in the vertebral half of asternal ribs, and the maximum values 332 and 132Bqkg(-1) fresh mass for a mixed sample composed of a cartilaginous tissue layer and parts of the perichondrium, both originating from asternal costal cartilages, respectively.

A compact, multidimensional spectrofluorometer exploiting supercontinuum generation

We report a novel, compact and automated multidimensional spectrofluorometer that exploits a fibre-laser-pumped ultrafast supercontinuum source to provide resolution with respect to intensity, excitation and emission wavelength, decay time and polarisation. This instrument has been applied to study the photophysics of the phase-sensitive membrane probe di-4-ANEPPDHQ and to characterise protein-protein interactions via Förster resonance energy transfer. It can be applied to in situ measurements via a fibre-optic probe in medical and other contexts and is demonstrated here to provide a comprehensive characterisation of tissue autofluorescence.

Mineralization of annexin-5-containing lipid-calcium-phosphate complexes: modulation by varying lipid composition and incubation with cartilage collagens

Matrix vesicles (MVs) in the growth plate bind to cartilage collagens and initiate mineralization of the extracellular matrix. Native MVs have been shown to contain a nucleational core responsible for mineral formation that is comprised of Mg(2+)-containing amorphous calcium phosphate and lipid-calcium-phosphate complexes (CPLXs) and the lipid-dependent Ca(2+)-binding proteins, especially annexin-5 (Anx-5), which greatly enhances mineral formation. Incorporation of non-Ca(2+)-binding MV lipids impedes mineral formation by phosphatidylserine (PS)-CPLX. In this study, nucleators based on amorphous calcium phosphate (with or without Anx-5) were prepared with PS alone, PS + phosphatidylethanolamine (PE), or PS + PE and other MV lipids. These were incubated in synthetic cartilage lymph containing no collagen or containing type II or type X collagen. Dilution of PS with PE and other MV lipids progressively retarded nucleation. Incorporation of Anx-5 restored nucleational activity to the PS:PE CPLX; thus PS and Anx-5 proved to be critical for nucleation of mineral. Without Anx-5, induction of mineral formation was slow unless high levels of Ca(2+) were used. The presence of type II collagen in synthetic cartilage lymph improved both the rate and amount of mineral formation but did not enhance nucleation. This stimulatory effect required the presence of the nonhelical telopeptides. Although type X collagen slowed induction, it also increased the rate and amount of mineral formation. Both type II and X collagens markedly increased mineral formation by the MV-like CPLX, requiring Anx-5 to do so. Thus, Anx-5 enhances nucleation by the CPLXs and couples this to propagation of mineral formation by the cartilage collagens.

Spectrocolorimetric assessment of cartilage plugs after autologous osteochondral grafting: correlations between color indices and histological findings in a rabbit model

We investigated the use of a commercial spectrocolorimeter and the application of two color models (L* a* b* colorimetric system and spectral reflectance distribution) to describe and quantify cartilage plugs in a rabbit model of osteochondral autografting. Osteochondral plugs were removed and then replaced in their original positions in Japanese white rabbits. The rabbits were sacrificed at 4 or 12 weeks after the operation and cartilage samples were assessed using a spectrocolorimeter. The samples were retrospectively divided into two groups on the basis of the histological findings (group H: hyaline cartilage, successful; group F: fibrous tissue or fibrocartilage, failure) and investigated for possible significant differences in the spectrocolorimetric analyses between the two groups. Moreover, the relationships between the spectrocolorimetric indices and the Mankin histological score were examined. In the L* a* b* colorimetric system, the L* values were significantly lower in group H than in group F (P = 0.02), whereas the a* values were significantly higher in group H than in group F (P = 0.006). Regarding the spectral reflectance distribution, the spectral reflectance percentage 470 (SRP470) values, as a coincidence index for the spectral reflectance distribution (400 to 470 nm in wavelength) of the cartilage plugs with respect to intact cartilage, were 99.8 +/- 6.7% in group H and 119.8 +/- 10.6% in group F, and the difference between these values was significant (P = 0.005). Furthermore, the a* values were significantly correlated with the histological score (P = 0.004, r = -0.76). The SRP470 values were also significantly correlated with the histological score (P = 0.01, r = 0.67). Our findings demonstrate the ability of spectrocolorimetric measurements to predict the histological findings of cartilage plugs after autologous osteochondral grafting. In particular, the a* values and SRP470 values can be used to judge the surface condition of an osteochondral plug on the basis of objective data. Therefore, spectrocolorimetry may contribute to orthopedics, rheumatology and related research in arthritis, and arthroscopic use of this method may potentially be preferable for in vivo assessment.

A cartilage ECM-derived 3-D porous acellular matrix scaffold for in vivo cartilage tissue engineering with PKH26-labeled chondrogenic bone marrow-derived mesenchymal stem cells

We developed a natural, acellular, 3-D interconnected porous scaffold derived from cartilage extracellular matrix (ECM). Human cartilage was physically shattered, then decellularized sequentially with use of hypotonic buffer, TritonX-100, and a nuclease solution and made into a suspension. The scaffold was fabricated by simple freeze-drying and cross-linking techniques. On histology, scaffolds showed most of the ECM components after removal of the cell fragments, and scanning electron microscopy revealed a 3-D interconnected porous structure. Cellular viability assay revealed no cytotoxic effects. In vitro study showed that the novel scaffold could provide a suitable 3-D environment to support the adheration, proliferation and differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) to chondrocytes in culture with chondrogenic medium after 21 days. Chondrogenically induced BMSCs labeled with fluorescent dye PKH26 were then grown on scaffolds and implanted subcutaneously into nude mice. Four weeks later, cartilage-like tissue formed, with positive staining for Safranin O, tuoluidine blue and collagen II. Cells in the samples seemed to confirm that they originated from the labeled BMSCs, as confirmed by in vivo fluorescent imaging and immunofluorescence examination. In conclusion, the cartilage ECM-derived porous scaffold shows potential as biomaterial for cartilage tissue engineering, and PKH26 fluorescent labeling and in vivo fluorescent imaging can be useful for cell tracking and analyzing cell-scaffold constructs in vivo.

Characterization of bovine patellar cartilage by NMR

Metabolic and structural changes in cartilage tissue are thought to be at the root of degenerative joint disease. We identify here the NMR resonances in bovine patellar cartilage tissue by static and high-resolution magic angle spinning (HRMAS) NMR spectroscopy, (1)H-(13)C heteronuclear single-quantum correlation (HSQC) spectroscopy, total correlation spectroscopy (TOCSY), and saturation transfer experiments. Some differences between the patellar cartilage samples studied here and earlier nasal cartilage and intervertebrate disc studies were found. In addition, we show assignments downfield of the water signal, which also includes the assignment of amide and hydroxy protons on the basis of their exchangeability with water. These results will allow an identification of spectroscopic markers of cartilage degradation using techniques such as chemical exchange saturation transfer imaging.

Biofunctional polymer nanoparticles for intra-articular targeting and retention in cartilage

The extracellular matrix of dense, avascular tissues presents a barrier to entry for polymer-based therapeutics, such as drugs encapsulated within polymeric particles. Here, we present an approach by which polymer nanoparticles, sufficiently small to enter the matrix of the targeted tissue, here articular cartilage, are further modified with a biomolecular ligand for matrix binding. This combination of ultrasmall size and biomolecular binding converts the matrix from a barrier into a reservoir, resisting rapid release of the nanoparticles and clearance from the tissue site. Phage display of a peptide library was used to discover appropriate targeting ligands by biopanning on denuded cartilage. The ligand WYRGRL was selected in 94 of 96 clones sequenced after five rounds of biopanning and was demonstrated to bind to collagen II alpha1. Peptide-functionalized nanoparticles targeted articular cartilage up to 72-fold more than nanoparticles displaying a scrambled peptide sequence following intra-articular injection in the mouse.